آزمایشگاه جداسازی وشناسایی ترکیبات آلی

آزمایشگاه جداسازی وشناسایی ترکیبات آلی

Chromatography

Pictured is a sophisticated gas chromatography system. This instrument records concentrations of acrylonitrile in the air at various points throughout the chemical laboratory.

Chromatography (from Greek χρῶμα chroma "color" and γράφειν graphein "to write") is the collective term for a set of laboratory techniques for the separation of mixtures. It involves passing a mixture dissolved in a "mobile phase" through a stationary phase, which separates the analyte to be measured from other molecules in the mixture based on differential partitioning between the mobile and stationary phases. Subtle differences in a compound's partition coefficient result in differential retention on the stationary phase and thus changing the separation.

Chromatography may be preparative or analytical. The purpose of preparative chromatography is to separate the components of a mixture for further use (and is thus a form of purification). Analytical chromatography is done normally with smaller amounts of material and is for measuring the relative proportions of analytes in a mixture. The two are not mutually exclusive.

 

History

Main article: History of chromatography

The history of chromatography begins during the mid-19th century. Chromatography, literally "color writing", was used—and named— in the first decade of the 20th century, primarily for the separation of plant pigments such as chlorophyll. New types of chromatography developed during the 1930s and 1940s made the technique useful for many types of separation process.

Chromatography became developed substantially as a result of the work of Archer John Porter Martin and Richard Laurence Millington Synge during the 1940s and 1950s. They established the principles and basic techniques of partition chromatography, and their work encouraged the rapid development of several types of chromatography method: paper chromatography, gas chromatography, and what would become known as high performance liquid chromatography. Since then, the technology has advanced rapidly. Researchers found that the main principles of Tsvet's chromatography could be applied in many different ways, resulting in the different varieties of chromatography described below. Simultaneously, advances continually improve the technical performance of chromatography, allowing the separation of increasingly similar molecules.

Chromatography terms

  • The analyte is the substance to be separated during chromatography.
  • Analytical chromatography is used to determine the existence and possibly also the concentration of analyte(s) in a sample.
  • A bonded phase is a stationary phase that is covalently bonded to the support particles or to the inside wall of the column tubing.
  • A chromatogram is the visual output of the chromatograph. In the case of an optimal separation, different peaks or patterns on the chromatogram correspond to different components of the separated mixture.

 

Plotted on the x-axis is the retention time and plotted on the y-axis a signal (for example obtained by a spectrophotometer, mass spectrometer or a variety of other detectors) corresponding to the response created by the analytes exiting the system. In the case of an optimal system the signal is proportional to the concentration of the specific analyte separated.

  • A chromatograph is equipment that enables a sophisticated separation e.g. gas chromatographic or liquid chromatographic separation.
  • Chromatography is a physical method of separation in which the components to be separated are distributed between two phases, one of which is stationary (stationary phase) while the other (the mobile phase) moves in a definite direction.
  • The eluate is the mobile phase leaving the column.
  • The eluent is the solvent that will carry the analyte.
  • An eluotropic series is a list of solvents ranked according to their eluting power.
  • An immobilized phase is a stationary phase which is immobilized on the support particles, or on the inner wall of the column tubing.
  • The mobile phase is the phase which moves in a definite direction. It may be a liquid (LC and CEC), a gas (GC), or a supercritical fluid (supercritical-fluid chromatography, SFC). The mobile phase consists of the sample being separated/analyzed and the solvent that moves the sample through the column. In the case of HPLC the mobile phase consists of a non-polar solvent(s) such as hexane in normal phase or polar solvents in reverse phase chromotagraphy and the sample being separated. The mobile phase moves through the chromatography column (the stationary phase) where the sample interacts with the stationary phase and is separated.
  • Preparative chromatography is used to purify sufficient quantities of a substance for further use, rather than analysis.
  • The retention time is the characteristic time it takes for a particular analyte to pass through the system (from the column inlet to the detector) under set conditions. See also: Kovats' retention index
  • The sample is the matter analyzed in chromatography. It may consist of a single component or it may be a mixture of components. When the sample is treated in the course of an analysis, the phase or the phases containing the analytes of interest is/are referred to as the sample whereas everything out of interest separated from the sample before or in the course of the analysis is referred to as waste.
  • The solute refers to the sample components in partition chromatography.
  • The solvent refers to any substance capable of solubilizing other substance, and especially the liquid mobile phase in LC.
  • The stationary phase is the substance which is fixed in place for the chromatography procedure. Examples include the silica layer in thin layer chromatography

Chromatography is based on the concept of partition coefficient. Any solute will partition between two immissible solvents. When we make one solvent immobile (by adsorption on a solid support matrix) and another mobile it results in most common applications of chromatography. If matrix support is polar (e.g. paper, sillica etc.) it is forward phase chromatography, and if it is non polar (C-18) it is reverse phase.

Techniques by chromatographic bed shape

Column chromatography

For more details on this topic, see Column chromatography.

Column chromatography is a separation technique in which the stationary bed is within a tube. The particles of the solid stationary phase or the support coated with a liquid stationary phase may fill the whole inside volume of the tube (packed column) or be concentrated on or along the inside tube wall leaving an open, unrestricted path for the mobile phase in the middle part of the tube (open tubular column). Differences in rates of movement through the medium are calculated to different retention times of the sample.[1]

In 1978, W. C. Still introduced a modified version of column chromatography called flash column chromatography (flash).[2][3] The technique is very similar to the traditional column chromatography, except for that the solvent is driven through the column by applying positive pressure. This allowed most separations to be performed in less than 20 minutes, with improved separations compared to the old method. Modern flash chromatography systems are sold as pre-packed plastic cartridges, and the solvent is pumped through the cartridge. Systems may also be linked with detectors and fraction collectors providing automation. The introduction of gradient pumps resulted in quicker separations and less solvent usage.

In expanded bed adsorption, a fluidized bed is used, rather than a solid phase made by a packed bed. This allows omission of initial clearing steps such as centrifugation and filtration, for culture broths or slurries of broken cells.

Planar chromatography

Thin layer chromatography is used to separate components of chlorophyll

Planar chromatography is a separation technique in which the stationary phase is present as or on a plane. The plane can be a paper, serving as such or impregnated by a substance as the stationary bed (paper chromatography) or a layer of solid particles spread on a support such as a glass plate (thin layer chromatography). Different compounds in the sample mixture travel different distances according to how strongly they interact with the stationary phase as compared to the mobile phase. The specific Retention factor (Rf) of each chemical can be used to aid in the identification of an unknown substance.

Paper chromatography

For more details on this topic, see Paper chromatography.

Paper chromatography is a technique that involves placing a small dot or line of sample solution onto a strip of chromatography paper. The paper is placed in a jar containing a shallow layer of solvent and sealed. As the solvent rises through the paper, it meets the sample mixture which starts to travel up the paper with the solvent. This paper is made of cellulose, a polar substance, and the compounds within the mixture travel farther if they are non-polar. More polar substances bond with the cellulose paper more quickly, and therefore do not travel as far.

Thin layer chromatography

For more details on this topic, see Thin layer chromatography.

Thin layer chromatography (TLC) is a widely employed laboratory technique and is similar to paper chromatography. However, instead of using a stationary phase of paper, it involves a stationary phase of a thin layer of adsorbent like silica gel, alumina, or cellulose on a flat, inert substrate. Compared to paper, it has the advantage of faster runs, better separations, and the choice between different adsorbents. For even better resolution and to allow for quantification, high-performance TLC can be used.

Displacement chromatography

The basic principle of displacement chromatography is: A molecule with a high affinity for the chromatography matrix (the displacer) will compete effectively for binding sites, and thus displace all molecules with lesser affinities.[4] There are distinct differences between displacement and elution chromatography. In elution mode, substances typically emerge from a column in narrow, Gaussian peaks. Wide separation of peaks, preferably to baseline, is desired in order to achieve maximum purification. The speed at which any component of a mixture travels down the column in elution mode depends on many factors. But for two substances to travel at different speeds, and thereby be resolved, there must be substantial differences in some interaction between the biomolecules and the chromatography matrix. Operating parameters are adjusted to maximize the effect of this difference. In many cases, baseline separation of the peaks can be achieved only with gradient elution and low column loadings. Thus, two drawbacks to elution mode chromatography, especially at the preparative scale, are operational complexity, due to gradient solvent pumping, and low throughput, due to low column loadings. Displacement chromatography has advantages over elution chromatography in that components are resolved into consecutive zones of pure substances rather than “peaks”. Because the process takes advantage of the nonlinearity of the isotherms, a larger column feed can be separated on a given column with the purified components recovered at significantly higher concentrations.

Techniques by physical state of mobile phase

Gas chromatography

For more details on this topic, see Gas chromatography.

Gas chromatography (GC), also sometimes known as Gas-Liquid chromatography, (GLC), is a separation technique in which the mobile phase is a gas. Gas chromatography is always carried out in a column, which is typically "packed" or "capillary" (see below) .

Gas chromatography (GC) is based on a partition equilibrium of analyte between a solid stationary phase (often a liquid silicone-based material) and a mobile gas (most often Helium). The stationary phase is adhered to the inside of a small-diameter glass tube (a capillary column) or a solid matrix inside a larger metal tube (a packed column). It is widely used in analytical chemistry; though the high temperatures used in GC make it unsuitable for high molecular weight biopolymers or proteins (heat will denature them), frequently encountered in biochemistry, it is well suited for use in the petrochemical, environmental monitoring and remediation, and industrial chemical fields. It is also used extensively in chemistry research.

Liquid chromatography

 

Preparative HPLC apparatus

Liquid chromatography (LC) is a separation technique in which the mobile phase is a liquid. Liquid chromatography can be carried out either in a column or a plane. Present day liquid chromatography that generally utilizes very small packing particles and a relatively high pressure is referred to as high performance liquid chromatography (HPLC).

In the HPLC technique, the sample is forced through a column that is packed with a stationary phase composed of irregularly or spherically shaped particles, a porous monolithic layer, or a porous membrane by a liquid (mobile phase) at high pressure. HPLC is historically divided into two different sub-classes based on the polarity of the mobile and stationary phases. Methods in which the stationary phase is more polar than the mobile phase (e.g. toluene as the mobile phase, silica as the stationary phase) are termed normal phase liquid chromatography (NPLC) and the opposite (e.g. water-methanol mixture as the mobile phase and C18 = octadecylsilyl as the stationary phase) is termed reversed phase liquid chromatography (RPLC). Ironically the "normal phase" has fewer applications and RPLC is therefore used considerably more.

Specific techniques which come under this broad heading are listed below. It should also be noted that the following techniques can also be considered fast protein liquid chromatography if no pressure is used to drive the mobile phase through the stationary phase. See also Aqueous Normal Phase Chromatography.

Affinity chromatography

For more details on this topic, see Affinity chromatography.

Affinity chromatography[5] is based on selective non-covalent interaction between an analyte and specific molecules. It is very specific, but not very robust. It is often used in biochemistry in the purification of proteins bound to tags. These fusion proteins are labeled with compounds such as His-tags, biotin or antigens, which bind to the stationary phase specifically. After purification, some of these tags are usually removed and the pure protein is obtained.

Affinity chromatography often utilizes a biomolecule's affinity for a metal (Zn, Cu, Fe, etc.). Columns are often manually prepared. Traditional affinity columns are used as a preparative step to flush out unwanted biomolecules.

However, HPLC techniques exist that do utilize affinity chromatogaphy properties. Immobilized Metal Affinity Chromatography (IMAC) is useful to separate aforementioned molecules based on the relative affinity for the metal (I.e. Dionex IMAC). Often these columns can be loaded with different metals to create a column with a targeted affinity.

Supercritical fluid chromatography

For more details on this topic, see Supercritical fluid chromatography.

Supercritical fluid chromatography is a separation technique in which the mobile phase is a fluid above and relatively close to its critical temperature and pressure.

Techniques by separation mechanism

Ion exchange chromatography

For more details on this topic, see Ion exchange chromatography.

Ion exchange chromatography (usually referred to as ion chromatography) uses an ion exchange mechanism to separate analytes based on their respective charges. It is usually performed in columns but can also be useful in planar mode. Ion exchange chromatography uses a charged stationary phase to separate charged compounds including anions, cations, amino acids, peptides, and proteins. In conventional methods the stationary phase is an ion exchange resin that carries charged functional groups which interact with oppositely charged groups of the compound to be retained. Ion exchange chromatography is commonly used to purify proteins using FPLC.

Size-exclusion chromatography

For more details on this topic, see Size-exclusion chromatography.

Size-exclusion chromatography (SEC) is also known as gel permeation chromatography (GPC) or gel filtration chromatography and separates molecules according to their size (or more accurately according to their hydrodynamic diameter or hydrodynamic volume). Smaller molecules are able to enter the pores of the media and, therefore, molecules are trapped and removed from the flow of the mobile phase. The average residence time in the pores depends upon the effective size of the analyte molecules. However, molecules that are larger than the average pore size of the packing are excluded and thus suffer essentially no retention; such species are the first to be eluted. It is generally a low-resolution chromatography technique and thus it is often reserved for the final, "polishing" step of a purification. It is also useful for determining the tertiary structure and quaternary structure of purified proteins, especially since it can be carried out under native solution conditions.

Special techniques

Reversed-phase chromatography

For more details on this topic, see Reversed-phase chromatography.

Reversed-phase chromatography is an elution procedure used in liquid chromatography in which the mobile phase is significantly more polar than the stationary phase.

This section requires expansion.

Two-dimensional chromatography

In some cases, the chemistry within a given column can be insufficient to separate some analytes. It is possible to direct a series of unresolved peaks onto a second column with different physico-chemical (Chemical classification) properties. Since the mechanism of retention on this new solid support is different from the first dimensional separation, it can be possible to separate compounds that are indistinguishable by one-dimensional chromatography. The sample is spotted at one corner of a square plate,developed, air-dried, then rotated by 90° and usually redeveloped in a second solvent system.

This section requires expansion.

Simulated moving-bed chromatography

For more details on this topic, see Simulated moving bed.

This section requires expansion.

Pyrolysis gas chromatography

Pyrolysis gas chromatography mass spectrometry is a method of chemical analysis in which the sample is heated to decomposition to produce smaller molecules that are separated by gas chromatography and detected using mass spectrometry.

Pyrolysis is the thermal decomposition of materials in an inert atmosphere or a vacuum. The sample is put into direct contact with a platinum wire, or placed in a quartz sample tube, and rapidly heated to 600 – 1000° C. Depending on the application even higher temperatures are used. Three different heating techniques are used in actual pyrolyzers: Isothermal furnace, inductive heating (Curie Point filament), and resistive heating using platinum filaments. Large molecules cleave at their weakest points and produce smaller, more volatile fragments. These fragments can be separated by gas chromatography. Pyrolysis GC chromatograms are typically complex because a wide range of different decomposition products is formed. The data can either be used as fingerprint to prove material identity or the GC/MS data is used to identify individual fragments to obtain structural information. To increase the volatility of polar fragments, various methylating reagents can be added to a sample before pyrolysis.

Besides the usage of dedicated pyrolyzers, pyrolysis GC of solid and liquid samples can be performed directly inside Programmable Temperature Vaporizer (PTV) injectors that provide quick heating (up to 30°C/sec) and high maximum temperatures of 600 - 650° C. This is sufficient for some pyrolysis applications. The main advantage is that no dedicated instrument has to be purchased and pyrolysis can be performed as part of routine GC analysis. In this case quartz GC inlet liners have to be used. Quantitative data can be acquired, and good results of derivatization inside the PTV injector are published as well.

Fast protein liquid chromatography

For more details on this topic, see Fast protein liquid chromatography.

Fast protein liquid chromatography (FPLC) is a term applied to several chromatography techniques which are used to purify proteins. Many of these techniques are identical to those carried out under high performance liquid chromatography, however use of FPLC techniques are typically for preparing large scale batches of a purified product.

Countercurrent chromatography

For more details on this topic, see Countercurrent chromatography.

Countercurrent chromatography (CCC) is a type of liquid-liquid chromatography, where both the stationary and mobile phases are liquids. It involves mixing a solution of liquids, allowing them to settle into layers and then separating the layers.

Chiral chromatography

Chiral chromatography involves the separation of stereoisomers. In the case of enantiomers, these have no chemical or physical differences apart from being three-dimensional mirror images. Conventional chromatography or other separation processes are incapable of separating them. To enable chiral separations to take place, either the mobile phase or the stationary phase must themselves be made chiral, giving differing affinities between the analytes. Chiral chromatography HPLC columns (with a chiral stationary phase) in both normal and reversed phase are commercially available

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RECYCLING

ORGANIC WASTE

Introduction

Organic waste is produced wherever there is human habitation. The main forms of organic waste are household food waste, agricultural waste, human and animal waste. In industrialised countries the amount of organic waste produced is increasing dramatically each year. Although many gardening enthusiasts ‘compost’ some of their kitchen and garden waste, much of the household waste goes into landfill sites and is often the most hazardous waste. The organic waste component of landfill is broken down by micro-organisms to form a liquid ‘leachate’ which contains bacteria, rotting matter and maybe chemical contaminants from the landfill. This leachate can present a serious hazard if it reaches a watercourse or enters the water table. Digesting organic matter in landfills also generates methane, which is a harmful greenhouse gas, in large quantity. Human organic waste is usually pumped to a treatment plant where it is treated, and then the effluent enters a watercourse, or it is deposited directly into the sea. Little effort is made to reclaim the valuable nutrient or energy content of this waste.

In developing countries, there is a different approach to dealing with organic waste. In fact, the word ‘waste’ is often an inappropriate term for organic matter, which is often put to good use. The economies of most developing countries dictates that materials and resources must be used to their full potential, and this has propagated a culture of reuse, repair and recycling. In many developing countries there exists a whole sector of recyclers, scavengers and collectors, whose business is to salvage ‘waste’ material and reclaim it for further use.

Where large quantities of waste are created, usually in the major cities, there are inadequate facilities for dealing with it, and much of this waste is either left to rot in the streets, or is collected and dumped on open land near the city limits. There are few environmental controls in these countries to prevent such practices.

There are a variety of ways of using organic waste and in this technical brief we hope to outline a few of the principle methods used for putting it to good use. The three main ways of using organic waste that we will look at are for soil improvement, for animal raising and to provide a source of energy.

Organic waste – types, sources and uses

As mentioned earlier, there a number of types of organic waste which are commonly discarded. Below we will look at the types and sources of organic waste and some examples of common uses for this waste.

Domestic or household waste

This type of waste is usually made up of food scraps, either cooked or uncooked, and garden waste such as grass cuttings or trimmings from bushes and hedges. Domestic kitchen waste is often mixed with non-organic materials such as plastic packaging, which cannot be composted. It is beneficial if this type of waste can be separated at source – this makes recycling of both types of waste far easier. Domestic or household waste is usually produced in relatively small quantities. In developing countries, there is a much higher organic content in domestic waste. From Figure 1 we can see that up to 60% (or more in some cases) of all municipal waste is organic matter, much higher than the figure for an industrialised country. It is therefore well worth intercepting this supply of useful material where it can be used effectively.

Recycling of organic waste Practical Action

0102030405060PaperGlass,ceramicsMetalsPlasticsLeather,rubberWood, bones,strawTextilesVegetablematterMiscellaneousDevelopingcountries -

frontIndustrialisedcountries -

back

Figure 1: Composition of municipal waste in a typical developing and industrialised country (actual figures vary significantly – this figure is only an example).

Commercially produced organic waste.

By this, we mean waste generated at institutional buildings, such as schools, hotels and restaurants. The quantities of waste here are much higher and the potential for use in conjunction with small-scale enterprise is good (see box 2).

Animal and human waste.

It is worth mentioning at the start of this section that there are serious health risks involved with handling sewage. Raw sewage contains bacteria and pathogens that cause serious illness and disease. It should be stressed that health and safety procedures should be followed when dealing with sewage and that people involved with its handling should have a clear understanding of the health risks involved. Raw sewage should never be applied to crops which are for consumption by humans or animals.

Human faecal residue is produced in large quantities in urban areas and is dealt with in a variety of ways. In the worst cases, little is done to remove or treat the waste and it can present enormous health risks. This is often the case in the slum districts or poor areas of some large cities. Sewage is often dealt with crudely and is pumped into the nearest water body with little or no treatment. There are methods for large-scale treatment and use of sewage as a fertiliser and a source of energy. The most commonly used method is anaerobic digestion to produce biogas and liquid fertiliser. Composting toilets (see later section) facilitate the conversion of human faecal waste into rich compost.

Animal residue is rarely wasted. This fertile residue is commonly used as a source of fertiliser, being applied directly to the land, or as a source of energy, either through direct combustion (after drying) or through digestion to produce methane gas.

Agricultural residue

This is the ‘waste’ which remains after the processing of crops (e.g. maize stalks, rice husks, foliage, etc.). There are a wide variety of applications for this residue, ranging from simple combustion on an open fire to complex energy production processes that use this waste as a fuel stock. It is not within the scope of this paper to deal with the many and varied uses of agricultural residues.

2

Recycling of organic waste Practical Action

Methods of processing organic waste

As mentioned in the introduction, there are three main ways in which organic waste can be used:

♦ soil improvement

♦ animal raising and

♦ to provide a source of energy

Differing levels of processing are required for achieving the above and in this section we will take a brief look at just some of the common approaches to using organic waste. Figure 2 below, shows some of the options in the form of a flow diagram.

Urban organic/ vegetable waste

Composting

Briquetting

Anaerobicdigestion

Compost toilets

Co-composting

Compost

Fertiliser

Fuel

Compost

Fuel

Animal feed

Compost

Human and animal waste

Figure 2: Processes and products from organic waste

Composting

Composting is simply the method of breaking down organic materials in a large container or heap. The decomposition occurs because of the action of naturally occurring micro-organisms such as bacteria and fungi. Small invertebrates, such as earthworms and millipedes, help to complete the process. Composting can convert organic waste into rich, dark coloured compost, or humus, in a matter of a few weeks or months. There is nothing mysterious or complicated about composting. Natural composting, or decomposition, occurs all the time in the natural world. Organic material, the remains of dead animals and plants, is broken down and consumed by micro-organisms and eaten by small invertebrates. Under controlled conditions, however, the process can be speeded up.

Composting has many benefits;

• It provides a useful way of reclaiming nutrients from organic refuse

• Saves valuable landfill space and possible contamination of land and water due to landfill ‘leachate’

• Can be used as fertiliser on farmland or in the garden

• Improves the condition of soils

In composting, provided the right conditions are present, the natural process of decay is speeded up. This involves controlling the composting environment and obtaining the following conditions:

3

Recycling of organic waste Practical Action

• The correct ratio of carbon to nitrogen. The correct ratio is in the range of 25 to 30 parts carbon to 1 part nitrogen (25:1 to 30:1). This is because the bacteria which carry out the composting process digest carbon twenty five to thirty times faster than they digest nitrogen. This is often seen as being a roughly equal amounts of "greens" and "browns". Carbon to nitrogen ratio will be referred to hereafter as the C:N ratio. The C:N ratio can be adjusted by mixing together organic materials with suitable contents.

• The correct amount of water. Plants have a liquid rather than a solid diet and therefore the compost pile should be kept moist at all times. On the other hand, a wet compost pile will produce only a soggy, smelly mess.

• Sufficient oxygen. A compost pile should be turned often to allow all parts of the pile to receive oxygen.

• The optimum pH level of the compost is between 5.5 and 8.

In these conditions, bacteria and fungi feed and multiply, giving off a great deal of heat. In well managed heaps, this temperature can reach as high as 60 C, which is sufficient to kill weed seeds and organisms that cause disease in plants and animals. While the temperature remains high, invertebrates are not present in compost heaps, but when the temperature drops, the invertebrates enter the heap from the surrounding soil and complete the process of decomposition.

Forms of decomposition

Anaerobic. In anaerobic decomposition, the breakdown of the organic material is caused by bacteria and fungi that thrive in low or no-oxygen conditions. It is the type of decomposition that takes place in closed containers. This type of system is more complex and difficult to control and requires complex equipment for larger scale composting (see Box 4).

Aerobic. In aerobic decomposition, bacteria and fungi which thrive in high oxygen conditions are responsible for the decomposition. This form of decomposition occurs in open heaps and containers that allow air to enter. With open heaps and more ventilated containers, compost can be formed in a matter of a few months, and even faster if the organic material is turned regularly. In heaps or bins where aerobic decomposition is occurring, there should be no unpleasant odours.

Some methods of composting

Composting systems can be opened or closed, that is the organic matter will either be placed in open piles or rows or in a closed container or reactor. The open system is rarely used in low-income countries due to its technical complexity, so we look at some of the open systems in use.

Backyard composting at the household level is a simple technique. It requires only suitable organic waste, space to construct the heap and time to carry out the necessary work. The waste can be placed in a pit (say 2m x 2m x 1m deep) and left to decompose for 2 – 3 months. Alternatively, the waste can be piled up within an enclosure of 4 poles and surrounded by boards or chicken wire and left for a similar period. This produces a rich compost which can be used as a fertiliser on fields or gardens.

Neighbourhood composting. A commonly used technique for neighbourhood composting is the use of windrows. Here waste is simply laid out in long rows and turned occasionally. Another method is the rotating bin method which uses a series of closed, aerated bins (see Lardinois3).

Co-composting is technique whereby organic food waste is mixed with human or animal excreta and composted Similar techniques are used to those described above. See Box 3 for an example of co-composting. There are many examples of successful co-composting systems throughout the world (see Lardinois3).

4

Recycling of organic waste Practical Action

Large-scale, centralised composting has tended to be unsuccessful in developing countries for a number of technical and organisational reasons. It is not dealt with in this paper.

Medium scale biogas and compost production from market garbage in Colombo, Sri Lanka

A pilot project being implemented by the Colombo Municipal Council uses organic waste from local city vegetable markets to produce biogas and compost. The digesters were developed by the National Energy Research and Development Centre and accept dry batches of organic waste. There are four 20 foot diameter floating dome digesters (see figure 3) each with a capacity of 40 tonnes dry waste. The residence time for the organic matter is 4 months and thus the four tanks are able to deal with a total of 480 tonnes of market waste each year.

The waste produces approximately 1 cubic metre of biogas per tonne per day and this translates to a total of 7500 kilowatt hours of electricity each year. The system also yields 300 tonnes of saleable fertiliser each year. Before this, all the waste had to be landfilled outside the city.

The digester is made from concrete with a floating fibreglass cover. The gas is piped from the digester and is used to power a 220 volt, 5 kilowatt converted engine. There is also a baker’s oven and a catering size gas burner at the site to demonstrate the uses of the gas.

Now we will look at an example of animal rearing using organic food scraps. This is a typical example of waste being put to good use and benefiting a number of groups.

Pig-feeding in Metro Manila

In the outlying urban areas of Manila, backyard pig- rearing has long been a traditional source of income. Commercially produced feed for this activity is expensive and pig raisers often turn to organic scraps to supplement or replace the commercial product. A network of collectors has developed that collects organic waste from restaurants in the city centre, and then distribute it amongst the backyard farmers. The farmers can purchase the scrap at about half the price of the commercial feed. A cost comparison carried out under the WAREN project (cited in a report titled ‘Recycling activities in Metro Manila’) shows that profit is more than doubled by feeding the pigs on organic scraps, even after all other costs, such as veterinary costs, transport, fuel, etc., are taken into consideration.

Such ventures are beneficial not only to the pig raisers, but also to the municipality who would otherwise have to dispose of the waste in a landfill.

Biogas production

Biogas is produced by means of a process known as anaerobic digestion. It is a process whereby organic matter is broken down by microbiological activity and takes place in the absence of air (anaerobic means ‘in the absence of air’). It is a phenomenon that occurs naturally at the bottom of ponds and marshes and gives rise to ‘marsh gas’ or methane, which is a combustible gas. It also takes place naturally in landfill sites and contributes to harmful greenhouse gases. Biogas can be produced by digesting human, animal or vegetable waste in specially designed digesters (see Box 2). Animal waste is particularly suitable for biogas production because it is often available is large quantities and also has a suitable C:N ratio. The scale of simple biogas plants can vary from a small ‘household’ system to large commercial plants of several thousand cubic metres. The process is sensitive to both temperature and feedstock (the correct C:N ratio is required as with composting) and both need to be controlled carefully for digestion to take place. Digestion time varies from a couple of weeks to a couple of months.

The digestion of waste yields several benefits:

• the production of methane for use as a fuel.

• the waste is reduced to slurry which has a high nutrient content which makes an

5

Recycling of organic waste Practical Action

ideal fertiliser; in some cases this fertiliser is the main product from the digester and the biogas is merely a by-product.

• during the digestion process pathogens in the manure are killed, which is a great benefit to environmental health.

Figure 3: a typical floating cover biogas digester

Two popular simple designs of digester have been developed for use in developing countries; the Indian ‘floating cover’ biogas digester (see figure 3 above) and the Chinese fixed dome digester. Both operate in the same way but the storage chambers have a slightly different design.

The residual slurry is removed at the outlet and can be used as a fertiliser. Biogas can be used for a number of applications, including lighting, cooking, electricity generation and as a replacement for diesel in diesel engines. Some countries have initiated large-scale biogas programmes, Tanzania being an example. The Tanzanian model is based on integrated resource recovery from municipal and industrial waste for grid-based electricity and fertiliser production (Karekezi 1997).

Waste Material

C:N Ratio

Gas yield (litres per kg)

Human excreta

6 – 10

-

Cow dung (up to 12kg per cow per day)

18

90 – 300

Pig manure (up to 2.5kg per pig per day)

-

370 – 500

Chicken manure

7

300

Grass (hay)

12

Not suitable alone

Grass with chicken manure

-

350

Paper

-

Not suitable alone

Paper with chicken manure

-

400 – 500

Sewage sludge

-

600

Wheat straw

150

Not suitable alone

Bagasse (sugar cane waste)

150

Not suitable alone

Sawdust

200 – 500

Not suitable alone

A gas-cooking burner needs 300 – 600 litres of gas per hour.

A peasant family uses 4000 – 5000 litres per month per person.

The ideal C:N ratio is between 25:1 and 30:1.

Table 1: Ability of waste to produce methane (Source: Vogler, Work from Waste)

6

Recycling of organic waste Practical Action

Composting toilet

There are a number of methods commonly used for home composting (or small-scale community composting) of human excreta. The simplest and most elegant solution is the composting toilet. Usually the design of such a toilet incorporates two chambers, each capable of holding at least one years deposit of excreta for the proposed site. No water is added to the chamber, but sawdust or ash can be added to improve the Carbon:Nitrogen ratio. When the first chamber is full it is sealed off and allowed to aerobically compost. The process produces a rich, pathogen-free compost. When the second chamber is full, the first chamber is emptied and the cycle begins again. For a single dwelling, the structure need be no bigger than that of a typical pit latrine. Other methods of home composting of excreta include co-composting with vegetable matter or anaerobic digestion in a biogas reactor (see later) or in a septic tank, which yield a rich slurry compost. For more information on these techniques see Franceys3.

Health, environment, and social aspects of waste reclamation

Waste collection and disposal is often seen as being the responsibility of the government or municipality. In many cases the municipality is unable to fulfil this role either due to financial constraints, lack of will or lack of organisational skills. In many cities, collection and separation of waste by the private or informal sector is seen as being too time consuming because of the content of the waste, often a mixture of organic and non-organic substances, such as plastic film. For there to emerge a successful organic waste reclamation process, it has been noted that it is of great help if the organic and non-organic waste is separated at source. It is here that the responsibility is thrown back onto the generator of the waste, the public. Many successful schemes are only successful because of community participation in the activities on a day-to-day basis. Where waste is separated at source, this lessens the risk of contamination from such items as batteries, means that the organic waste is cleaner (and will therefore fetch a higher price), it is easier to sort and the incidence of injury and disease related to sorting is decreased. There are a number of good examples of community recycling or resource recovery schemes in developing countries. Two such schemes are outlined below.

Accra, Ghana

In the Ghanaian capital, Accra, small-scale composting of domestic waste has been introduced to help ease the waste situation. The project has been running since 1985 with 3 collection points in low-income districts. As soon as it arrives at the collection points (delivered by workers from the city’s waste management department) the waste is pre-sorted – immediately reusable material is separated from organic waste. More solid waste is removed after the compost has been turned over for the first time. The waste is sorted a further two times during the composting process and finally sieved before being sold by the container-load to local farmers. (GATE Questions and Answers No3/89).

Mérida, Mexico

In early 1978 a new drainage and recycling system was commissioned as part of a new low-cost housing project in Mérida, a city in south-eastern Mexico. The system is known as SIRDO (Sistema Integrada para la Reciclaje de Derecho Organico - Integrated System for Organic Waste Recycling). Each house is connected to a drainage system that distinguishes between grey (washing) and black (toilet) water. The grey water is filtered and used for irrigation, and the solids in the black water are settled out and used in a co-composting process (with household waste) to produce a nutrient rich, dry-powder fertiliser. The dual chamber system yields compost every 6 months. The treated black water is also used for irrigation.

The system was designed to be managed by the community. In the early days there was considerable opposition to the system, not only from the community but also from the local council and private companies, but this soon dissipated as it became clear that the system improved the communities sanitation and yielded a good quality saleable compost.

7

Recycling of organic waste Practical Action

The system is maintained by community members on a voluntary basis and revenue from the sale of compost (usually to middle class residents for garden use) is reinvested in micro-enterprises or used to pay for larger maintenance jobs.

Where the informal sector carries out reclamation activities there is also a direct benefit to the municipality. A reduction in the quantity of refuse to be collected means a proportional reduction in the collection costs. Some progressive authorities actually encourage collection by members of the informal sector and will provide facilities to aid community recycling, as it is realised that it is cheaper than collection and disposal of waste. The municipality also often realise the value of contracting the work of collection and disposal to private companies. In Bogota, a city of 4 million people in Colombia with a waste generation level of 0.5kg per capita per day, it has been estimated that the cost of public waste collection is approximately US$35 per tonne whereas the private sector can make the collection for US$17 per tonne, less than half the cost.

There is often a health benefit when the municipality supports the local informal sector in recycling activities. With proper facilities for collection and processing of waste, many of the health hazards associated with this work can be removed or reduced.

Where the refuse collection activities are carried out by members of the informal sector, this is usually characterised by a complex network of interrelated activities. There is usually a hierarchy of scavengers, collectors, middlemen, dealers, small-scale recycling activities, micro-enterprise, etc. One of the most institutionalised scavenging systems in the world exists in Cairo, Egypt. There, a group of former oasis dwellers, called Wahis, have controlled garbage collection for the last 100 years. Another group, the Zabaleen, pay a fee to the Wahi for the right to collect garbage. The Zabaleen, with less than one third of the staff of the municipal sanitation department, collect 1,600 tons of trash each day to the cities 1,450 tons. Even so, 15% of the cities rubbish piles up in the streets. The Zabaleen haul home the day’s receipts in donkey carts. Later, in residential courtyards, the women and children of the household sort the trash. Organic materials feed the pigs – their primary income earners – while glass, paper, plastics, metal and cloth are sold. A report has suggested that systematic garbage collection by the city would cost more than the entire municipal budget. Without the Zabaleen, much of the city’s waste would simply not be collected (Worldwatch Paper 76).

 

 

+ نوشته شده در  یکشنبه یکم خرداد 1390ساعت 13:41  توسط ساناز رضائی معصومه سرافراز  | 

Material Safety Data Sheet
Ninhydrin, reagent ACS
ACC# 01021
Section 1 - Chemical Product and Company Identification
MSDS Name: Ninhydrin, reagent ACS
Catalog Numbers: AC415720000, AC415720100, AC415720250
Synonyms: 1,2,3-Indantrione; 1,2,3-Triketohydrindene; 2,2-Dihydroxy-1,3-indandione; 2,2-Dihydroxy-1H-indene-1,3(2H)-dione; 1H-Indene-1,2,3-trione.
Company Identification:
              Acros Organics N.V.
              One Reagent Lane
              Fair Lawn, NJ 07410
For information in North America, call: 800-ACROS-01
For emergencies in the US, call CHEMTREC: 800-424-9300

Section 2 - Composition, Information on Ingredients

CAS# Chemical Name Percent EINECS/ELINCS
485-47-2 Ninhydrin 100.0 207-618-1

Hazard Symbols: XN
Risk Phrases: 22 36/37/38

Section 3 - Hazards Identification

EMERGENCY OVERVIEW

Appearance: slightly yellow. Light sensitive. Causes eye and skin irritation. Warning! Causes respiratory tract irritation. Harmful if swallowed. May be harmful if absorbed through skin or if inhaled.
Target Organs: Eyes, skin, mucous membranes.


Potential Health Effects
Eye: Causes eye irritation.
Skin: Causes skin irritation. May cause skin sensitization, an allergic reaction, which becomes evident upon re-exposure to this material. May be harmful if absorbed through the skin. May cause reddening of the skin.
Ingestion: Harmful if swallowed. May cause irritation of the digestive tract. The toxicological properties of this substance have not been fully investigated.
Inhalation: The toxicological properties of this substance have not been fully investigated. May be harmful if inhaled. Inhalation of dust causes respiratory tract irritation with cough and sore throat.
Chronic: No information found.

Section 4 - First Aid Measures

Eyes: In case of contact, immediately flush eyes with plenty of water for at least 15 minutes. Get medical aid.
Skin: In case of contact, immediately flush skin with soap and plenty of water. Remove contaminated clothing and shoes. Get medical aid if symptoms occur. Wash clothing before reuse.
Ingestion: If swallowed, do not induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. Get medical aid.
Inhalation: If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical aid.
Notes to Physician: Treat symptomatically and supportively.

Section 5 - Fire Fighting Measures

General Information: As in any fire, wear a self-contained breathing apparatus in pressure-demand, MSHA/NIOSH (approved or equivalent), and full protective gear. Dusts at sufficient concentrations can form explosive mixtures with air.
Extinguishing Media: Use water spray, dry chemical, carbon dioxide, or chemical foam.

Section 6 - Accidental Release Measures

General Information: Use proper personal protective equipment as indicated in Section 8.
Spills/Leaks: Vacuum or sweep up material and place into a suitable disposal container. Avoid generating dusty conditions. Provide ventilation.

Section 7 - Handling and Storage

Handling: Wash thoroughly after handling. Remove contaminated clothing and wash before reuse. Use with adequate ventilation. Minimize dust generation and accumulation. Avoid contact with eyes, skin, and clothing. Keep container tightly closed. Avoid ingestion and inhalation.
Storage: Do not store in direct sunlight. Store in a tightly closed container. Store in a cool, dry, well-ventilated area away from incompatible substances. Store protected from light. Refrigeration has been recommended.

Section 8 - Exposure Controls, Personal Protection

Engineering Controls: Facilities storing or utilizing this material should be equipped with an eyewash facility and a safety shower. Use adequate ventilation to keep airborne concentrations low.
Exposure Limits
Chemical Name ACGIH NIOSH OSHA - Final PELs
Ninhydrin none listed none listed none listed

OSHA Vacated PELs: Ninhydrin: No OSHA Vacated PELs are listed for this chemical.
Personal Protective Equipment
Eyes: Wear appropriate protective eyeglasses or chemical safety goggles as described by OSHA's eye and face protection regulations in 29 CFR 1910.133 or European Standard EN166.
Skin: Wear appropriate protective gloves to prevent skin exposure.
Clothing: Wear appropriate protective clothing to prevent skin exposure.
Respirators: Follow the OSHA respirator regulations found in 29CFR 1910.134 or European Standard EN 149. Always use a NIOSH or European Standard EN 149 approved respirator when necessary.

Section 9 - Physical and Chemical Properties

Physical State: Crystalline powder
Appearance: slightly yellow
Odor: characteristic odor
pH: Not available.
Vapor Pressure: Negligible.
Vapor Density: 6.16 (air=1)
Evaporation Rate:Not applicable.
Viscosity: Not available.
Boiling Point: Not available.
Freezing/Melting Point:466 deg F (dec)
Autoignition Temperature: Not applicable.
Flash Point: Not applicable.
Decomposition Temperature:466 deg F
NFPA Rating: (estimated) Health: 2; Flammability: 1; Reactivity: 0
Explosion Limits, Lower:Not available.
Upper: Not available.
Solubility: Soluble in water.
Specific Gravity/Density:0.86
Molecular Formula:C9H6O4
Molecular Weight:178.14

Section 10 - Stability and Reactivity

Chemical Stability: Stable under normal temperatures and pressures. May discolor on exposure to light. Ninhydrin becomes anhydrous with reddening at 257°F, swells at 282°F and decomposes at 466°F. Ninhydrin is sensitive to prolonged exposure to light. UV spectrophotometric stability screening indicates that solutions of this compound in ethanol are stable for at least 24 hours.
Conditions to Avoid: High temperatures, light, dust generation.
Incompatibilities with Other Materials: Strong oxidizing agents, bases, amines.
Hazardous Decomposition Products: Carbon monoxide, carbon dioxide.
Hazardous Polymerization: Will not occur.

Section 11 - Toxicological Information

RTECS#:
CAS# 485-47-2: NK5425000
LD50/LC50:
Not available.

Carcinogenicity:
CAS# 485-47-2: Not listed by ACGIH, IARC, NIOSH, NTP, or OSHA.
Epidemiology: No information found.
Teratogenicity: No information found.
Reproductive Effects: No information found.
Neurotoxicity: No information found.
Mutagenicity: No information found.
Other Studies: See actual entry in RTECS for complete information.

Section 12 - Ecological Information

Ecotoxicity: No data available. No information available.
Environmental: No information available.
Physical: Log P (octanol-water): 0.67
Other: No information available.

Section 13 - Disposal Considerations
Chemical waste generators must determine whether a discarded chemical is classified as a hazardous waste. US EPA guidelines for the classification determination are listed in 40 CFR Parts 261.3. Additionally, waste generators must consult state and local hazardous waste regulations to ensure complete and accurate classification.
RCRA P-Series: None listed.
RCRA U-Series: None listed.

Section 14 - Transport Information

US DOT IATA RID/ADR IMO Canada TDG
Shipping Name: No information available.


No information available.
Hazard Class:




UN Number:




Packing Group:





Section 15 - Regulatory Information
US FEDERAL

TSCA
CAS# 485-47-2 is listed on the TSCA inventory.
Health & Safety Reporting List
None of the chemicals are on the Health & Safety Reporting List.
Chemical Test Rules
None of the chemicals in this product are under a Chemical Test Rule.
Section 12b
None of the chemicals are listed under TSCA Section 12b.
TSCA Significant New Use Rule
None of the chemicals in this material have a SNUR under TSCA.
SARA

Section 302 (RQ)
None of the chemicals in this material have an RQ.
Section 302 (TPQ)
None of the chemicals in this product have a TPQ.
SARA Codes
CAS # 485-47-2: acute.
Section 313
No chemicals are reportable under Section 313.
Clean Air Act:
This material does not contain any hazardous air pollutants. This material does not contain any Class 1 Ozone depletors. This material does not contain any Class 2 Ozone depletors.
Clean Water Act:
None of the chemicals in this product are listed as Hazardous Substances under the CWA. None of the chemicals in this product are listed as Priority Pollutants under the CWA. None of the chemicals in this product are listed as Toxic Pollutants under the CWA.
OSHA:
None of the chemicals in this product are considered highly hazardous by OSHA.
STATE
CAS# 485-47-2 is not present on state lists from CA, PA, MN, MA, FL, or NJ.
California No Significant Risk Level: None of the chemicals in this product are listed. European/International Regulations
European Labeling in Accordance with EC Directives
Hazard Symbols:
XN
Risk Phrases:

R 22 Harmful if swallowed.
R 36/37/38 Irritating to eyes, respiratory system
and skin.

Safety Phrases:

S 26 In case of contact with eyes, rinse immediately
with plenty of water and seek medical advice.
S 28A After contact with skin, wash immediately with
plenty of water.

WGK (Water Danger/Protection)

CAS# 485-47-2: 2
Canada
CAS# 485-47-2 is listed on Canada's DSL List. CAS# 485-47-2 is listed on Canada's DSL List.
This product has a WHMIS classification of D1B, D2B.
CAS# 485-47-2 is not listed on Canada's Ingredient Disclosure List.
Exposure Limits

Section 16 - Additional Information
MSDS Creation Date: 9/23/1998
Revision #3 Date: 11/17/2000
The information above is believed to be accurate and represents the best information currently available to us. However, we make no warranty of merchantability or any other warranty, express or implied, with respect to such information, and we assume no liability resulting from its use. Users should make their own investigations to determine the suitability of the information for their particular purposes. In no event shall Fisher be liable for any claims, losses, or damages of any third party or for lost profits or any special, indirect, incidental, consequential or exemplary damages, howsoever arising, even if Fisher has been advised of the possibility of such damages.

+ نوشته شده در  دوشنبه بیست و ششم اردیبهشت 1390ساعت 20:35  توسط ساناز رضائی معصومه سرافراز  | 

Chapter 27: Amino Acids, Peptides and Proteins Ch 27 contents

Ninhydrin Test

  • Amines (including α-amino acids) react with ninhydrin to give a coloured product.
  • It can be used qualitatively (e.g. for chromatographic visualisation) or quantitatively (e.g. for peptide sequencing).
  • The α-amino acids typically give a blue-purple product.
  • Proline, a secondary amine, gives a yellow-orange product.
  • The test is sensitive enough that ninhydrin can be used for the visualisation of fingerprints.
+ نوشته شده در  دوشنبه بیست و ششم اردیبهشت 1390ساعت 20:31  توسط ساناز رضائی معصومه سرافراز  | 

Copper Complex Formation



 

Amino Acid

Copper complex formation for amino acids.


 

Procedure

A small amount of the compound is dissolved in 1 mL of water. Two drops of 1 M copper(II) sulfate are added. If a blue color is not formed immediately, then heat the test tube in a hot water bath for 5 min.

Positive Test

A moderate to deep blue color of a liquid or a dark blue solid is a positive test.

Complications

Some a-amino acids are not very soluble in cold water. However, these amino acids are soluble in hot water and will give a positive test when the solution is heated. Aliphatic amines yield a blue precipitate. Anilines give a brown or green color, but other aromatic amines produce a blue-purple color.

+ نوشته شده در  یکشنبه بیست و پنجم اردیبهشت 1390ساعت 23:43  توسط ساناز رضائی معصومه سرافراز  | 

Acid hydrolysis using sulphuric acid and water (equilibrium reaction). The ester splits into a carboxylic acid and alcohol, protons donated from the acid. The solution can then be distilled and the remaining acid can be checked using UV indicator.

Acid hydrolysis using sulphuric acid and water (equilibrium reaction). The ester splits into a carboxylic acid and alcohol, protons donated from the acid. The solution can then be distilled and the remaining acid can be checked using UV indicator.

Esters RCOOR'

R = H, alkyl or aryl

R' = alkyl or aryl

There is no simple test for an ester. Usually a colourless liquid with a pleasant 'odour'.

The ester can be reacted with saturated ethanolic hydroxylamine hydrochloride + 20% methanolic KOH and gently heated until boiling. Then mixture acidified with 1M HCl(aq) and FeCl3(aq) added dropwise. Deep red or purple colour formed. The test depends on the formation of a hydroxamic acid R-C(=NOH)OH which forms coloured salts with Fe3+(aq) ion. The reaction is also given by acid chlorides and acid anhydrides, and phenols give a purple colour with iron(III) chloride, so frankly, the test is not that good. This test is not likely to be expected 
Iodoform test

The formation of CHI3, triiodomethane (or old name 'iodoform'.

NaOH(aq) is added to a solution of iodine in potassium iodide solution until most of the colour has gone. The organic compound is warmed with this solution. A yellow solid is formed with the smell of an antiseptic, CHI3, tri-iodomethane, melting point 119oC. This reaction is given by the alcohol ethanol CH3CH2OH and all alcohols with the 2-ol structure -CHOH-CH3 and

the aldehyde ethanal CH3CHO and all ketones with the 2-one structure R-CO-CH3  ('methyl ketones')

Its a combination of halogenation and oxidation and is not a definitive test for anything, it just indicates a possible part of a molecules structure.Advanced Chemistry Page Index and Links

Refrense:

Read more: http://wiki.answers.com/Q/How_do_you_test_for_a_ester#ixzz1ekUawXtl
+ نوشته شده در  یکشنبه بیست و پنجم اردیبهشت 1390ساعت 23:41  توسط ساناز رضائی معصومه سرافراز  | 

NaOH Treatment



 

Ammonium Salt

NaOH treatment for ammonium salts.

Amine Salt

NaOH treatment for amine salts.


 

Procedure

Place 5 mL of 10% sodium hydroxide solution in a test tube, add 0.2-0.4 g of the compound, and shake the mixture vigorously. Note the odor of ammonia or the formation of an oily layer of the amine. Moistened pink litmus paper placed in the vapor above the solution will turn blue if ammonia or a volatile amine is present.

Positive Test

ammonium salts - ammonia smell is a positive test.

amine salts - separation of an oily layer of the amine is a positive test.

Complications

None.



 

Nitro Compounds

NaOH treatment for nitro compounds.


 

Procedure

To 5 mL of 20% sodium hydroxide solution add 2 mL of ethanol and a drop or a crystal of the unknown, and shake vigorously. Note the color of the solution.

Positive Test

mononitro compounds - light yellow color is a positive test.

dinitro compounds - bluish purple color is a positive test.

trinitro compounds - blood red color is a positive test.

Complications

The presence of amino or hydroxyl groups inhibits the formation of these colored solutions.

+ نوشته شده در  یکشنبه بیست و پنجم اردیبهشت 1390ساعت 23:20  توسط ساناز رضائی معصومه سرافراز  | 

Sodium Detection of Active Hydrogen



Alcohol

Sodium detection for alcohols.

Amine

Sodium detection for amines.

Alkyne

Sodium detection for alkynes.


Procedure

To 0.25 mL or 0.25 g of the sample, add small thin slices of freshly cut sodium until no more will dissolve. Evolution of hydrogen gas indicates the presence of an acidic hydrogen, such as a hydroxyl group in an alcohol, a hydrogen attached to the nitrogen in a primary or secondary amine, or a hydrogen in a terminal alkyne. Cool the solution, and observe. Add an equal volume of ether. Another positive test is the formation of the solid salt. Liquid samples should be dried with calcium sulfate, prior to testing. This test may be applied to solid compounds or very viscous liquids by dissolving them in an inert solvent such as anhydrous ligroin or toluene.

Positive Test

Formation of hydrogen gas is a positive test.

Complications

Dealing with sodium metal can be exciting. Make sure that all samples are dry before proceeding with test.

+ نوشته شده در  یکشنبه بیست و پنجم اردیبهشت 1390ساعت 23:19  توسط ساناز رضائی معصومه سرافراز  | 

Nitrous Acid Test



1o Aliphatic Amine

Nitrous acid test for primary aliphatic amine.

1o Aromatic Amine

Nitrous acid test for primary aromatic amine.

2o Amine

Nitrous acid test for secondary amine.

3o Aliphatic Amine

Nitrous acid test for tertiary aliphatic amine.

3o Aromatic Amine

Nitrous acid for tertiary aromatic amine.

Amino Acid

Nitrous acid for amino acid.


Procedure

Dissolve 0.5 mL or 0.5 g of unknown in 1.5 mL of conc. HCl diluted with 2.5 mL of water, and cool the solution to 0oC in a beaker of ice. Dissolve 0.5 g of sodium nitrite in 2.5 mL of water and add this solution dropwise, with shaking, to the cold solution of the amine hydrochloride. Continue the addition until the mixture gives a positive test for nitrous acid. The test is carried out by placing a drop of the solution on starch-iodide paper; a blue color indicates the presence of nitrous acid. If the test is positive, move 2 mL of the solution to another test tube, warm gently, and examine for evolution of gas.

Positive Test

1o aliphatic amines- rapid bubbling upon addition of sodium nitrite is a positive test.

1o aromatic amines- rapid bubbling after addition of sodium nitrite (with heating) is a positive test.

2o amines- pale yellow oil with no evolution of gas is a positive test.

3o aliphatic amines- immediate positive test for nitrous acid with no evolution of gas is a positive test.

3o aromatic amines- dark-orange solution or orange solid, when treated with base turns green is a positive test.

Complications

Compounds having a methylene group adjacent to a carbonyl group give a positive test.

Alkyl mercaptans yield red thionitroso compounds.

Nitrous acid will react with amides and phenols.

+ نوشته شده در  یکشنبه بیست و پنجم اردیبهشت 1390ساعت 23:18  توسط ساناز رضائی معصومه سرافراز  | 

Nickel Chloride and 5-Nitrosalicylaldehyde Test



2o Amine

Nickel chloride test for amine.


Procedure

Add 1 or 2 drops or 50 mg of unknown to 5 mL of water. If necessary, 1 or 2 drops of conc. HCl may be added to dissolve the amine. Add 0.5 mL of amine solution to 3 mL of the nickel chloride and 5-nitrosalicylaldehyde reagent. To make reagent: to 15 mL of triethanolamine is added a solution of 0.5 g of 5-nitrosalicylaldehyde dissolved in 25 mL of water. Then 0.5 g of nickel chloride hexahydrate dissolved in 10 mL of water is added, and the total volume of the solution is brought to 100 mL.

Positive Test

1o aliphatic amines- immediate copious precipitate is a positive test.

1o aromatic amines- copious precipitate (after 2 - 3 minutes) is a positive test.

Complications

Extremely sensitive reagent and could give erroneous results.

Hydroxyl amines and hydrazines give positive test.

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Nickel Chloride, Carbon Disulfide, Ammonium Hydroxide Test



2o Amine

Nickel chloride test for secondary amine.


Procedure

Add 1 or 2 drops or 50 mg of unknown to 5 mL of water. If necessary, 1 or 2 drops of conc. HCl may be added to dissolve the amine. To 1 mL of nickel chloride in carbon disulfide reagent in a test tube, add 0.5 - 1 mL of conc. ammonium hydroxide, followed by 0.5 - 1 mL of amine solution.

Positive Test

2o amines- precipitate is a positive test.

Complications

Primary and tertiary amines with secondary amine impurities will yield a positive test

+ نوشته شده در  یکشنبه بیست و پنجم اردیبهشت 1390ساعت 23:15  توسط ساناز رضائی معصومه سرافراز  | 

Hinsberg Test



1o Amine

Hinsberg test for primary amine.

2o Amine

Hinsberg test for secondary amine.

3o Amine

Hinsberg test for tertiary amine.


Procedure

To 0.3 mL or 300 mg of unknown in a test tube, add 5 mL of 10% NaOH solution and 0.4 mL of benzenesulfonyl chloride. Stopper the test tube, and shake the mixture vigorously. Test the solution to make sure that it is still alkaline. After all of the benzenesulfonyl chloride has reacted, cool the solution and separate the residue, if present, from the solution. Test the residue for solubility in 10% HCl solution. If no residue remains, then treat the solution with 10% HCl solution and observe whether a precipitate forms.

Positive Test

1o amines - dissolves in base and precipitates from acid is a positive test.

2o amines - precipitates from base and no change from acid is a positive test.

3o amines - precipitates from base and dissolves in acid is a positive test.

Complications

Amphoteric compounds give erroneous results.

Some sodium salts of benzenesulfonamides of primary amines are insoluble in the Hinsberg solution and may appear to be secondary amines.

Some tertiary amine hydrochloride salts are insoluble in dilute HCl and water and may also appear to be secondary amines.

+ نوشته شده در  یکشنبه بیست و پنجم اردیبهشت 1390ساعت 23:14  توسط ساناز رضائی معصومه سرافراز  | 

Acetyl chloride test for alcohol.

Phenol

Acetyl chloride test for phenol.

1o amine

Acetyl chloride test for primary amine.

2o amine

Acetyl chloride test for secondary amine.


 

Procedure

In hood: Add drop by drop 0.2 mL of acetyl chloride to 0.2 mL or 0.2 g of the unknown. Allow the mixture to stand for a minute or two and then pour it cautiously into 1 mL of water.

Positive Test

Evolution of heat and HCl gas or a precipitate is a positive test.

Alcohols and phenols produce esters indicated by the formation of a top layer in the flask.

Primary and secondary amines form amides which precipitate.

Complications

Moisture present in the unknown will give positive test.

+ نوشته شده در  یکشنبه بیست و پنجم اردیبهشت 1390ساعت 23:11  توسط ساناز رضائی معصومه سرافراز  | 

Amine

From Wikipedia, the free encyclopedia

Primary amine Secondary amine Tertiary amine
primary amine
secondary amine
tertiary amine
Jump to: navigation, search

For other uses, see Amine (disambiguation).

Primary amine

Secondary amine

Tertiary amine

 

Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group.[1] Important amines include amino acids, biogenic amines, trimethylamine, and aniline; see Category:Amines for a list of amines. Inorganic derivatives of ammonia are also called amines, such as chloramine (NClH2).

Compounds with the nitrogen atom attached to a carbonyl of the structure R-C(=O)NR'R'‌' are called amides and have different chemical properties from amines.

Contents

[hide]

[edit] Classes of amines

[edit] Aliphatic amines

Primary amines arise when one of three hydrogen atoms in ammonia is replaced by an alkyl. Important primary alkyl amines include methylamine, ethanolamine (2-aminoethanol), and the buffering agent tris). Secondary amines have two alkyl substituents bound to N together with one hydrogen. Important representatives include dimethylamine and methylethanolamine. In tertiary amines, all three hydrogen atoms are replaced by organic substituents. Examples include trimethylamine, a distinctively fishy smell. Cyclic amines are either secondary or tertiary amines. Examples of cyclic amines include the 3-member ring aziridine and the six-membered ring piperidine. N-methylpiperidine is a cyclic tertiary amine. It is also possible to have four alkyl substituents on the nitrogen. These compounds are not amines but are called quaternary ammonium cations, have a charged nitrogen center, and necessarily come with an anion.

[edit] Aromatic amines

Main article: Aromatic amine

Aromatic amines have the nitrogen atom connected to an aromatic ring as in anilines. The aromatic ring decreases the alkalinity of the amine, depending on its substituents. The presence of an amine group strongly increases the reactivity of the aromatic ring, due to an electron-donating effect.

[edit] Naming conventions

Amines are named in several ways. Typically, the compound is given the prefix "amino-" or the suffix: "-amine." The prefix "N-" shows substitution on the nitrogen atom. An organic compound with multiple amino groups is called a diamine, triamine, tetraamine and so forth.

Systematic names for some common amines:

Lower amines are named with the suffix -amine.


methylamine
Primary amine Secondary amine Tertiary amine
primary amine
secondary amine
tertiary amine

Higher amines have the prefix amino as a functional group.


2-aminopentane
(or sometimes: pent-2-yl-amine or pentane-2-amine)

[edit] Physical properties

Hydrogen bonding significantly influences the properties of primary and secondary amines.[2] Thus the boiling point of amines is higher than those of the corresponding phosphines, but generally lower than those of the corresponding alcohols. For example, methylamine and ethylamine are gases under standard conditions, whereas the corresponding methyl alcohol and ethyl alcohols are liquids. Gaseous amines possess a characteristic ammonia smell, liquid amines have a distinctive "fishy" smell.

Also reflecting their ability to form hydrogen bonds, most aliphatic amines display some solubility in water. Solubility decreases with the increase in the number of carbon atoms. Aliphatic amines display significant solubility in organic solvents, especially polar organic solvents. Primary amines react with ketones such as acetone.

The aromatic amines, such as aniline, have their lone pair electrons conjugated into the benzene ring, thus their tendency to engage in hydrogen bonding is diminished. Their boiling points are high and their solubility in water low

[edit] Chirality

Amines of the type NHRR' and NRR'R" are chiral: the nitrogen atom bears four substituents counting the lone pair. The energy barrier for the inversion of the stereocenter is relatively low, e.g., ~7 kcal/mol for a trialkylamine. The interconversion of the stereoisomers has been compared to the inversion of an open umbrella in to a strong wind. Because of this low barrier, amines such as NHRR' cannot be resolved optically and NRR'R" can only be resolved when the R, R', and R" groups are constrained in cyclic structures such as aziridines. Quaternary ammonium salts with four distinct groups on the nitrogen are capable of exhibiting optical activity.

[edit] Properties as bases

Like ammonia, amines are bases. Compared to alkali metal hydroxides, amines are weaker (see table for examples of conjugate acid Ka values). The basicity of amines depends on:

  1. The electronic properties of the substituents (alkyl groups enhance the basicity, aryl groups diminish it).
  2. Steric hindrance offered by the groups on nitrogen.
  3. The degree of solvation of the protonated amine.

The nitrogen atom features a lone electron pair that can bind H+ to form an ammonium ion R3NH+. The lone electron pair is represented in this article by a two dots above or next to the N. The water solubility of simple amines is largely due to hydrogen bonding between protons in the water molecules and these lone electron pairs.

Ions of compound

Kb

Ammonia NH3

1.8·10−5 M

Propylamine CH3CH2CH2NH2

4.7·10−4 M

2-Propylamine (CH3)2CHNH2

3.4·10−4 M

Methylamine CH3NH2

4.4·10−4 M

Dimethylamine (CH3)2NH

5.4·10−4 M

Trimethylamine (CH3)3N

5.9·10−5 M

+I effect of alkyl groups raises the energy of the lone pair of electrons, thus elevating the basicity. Thus the basicity of an amine may be expected to increase with the number of alkyl groups on the amine. However, there is no strict trend in this regard, as basicity is also governed by other factors mentioned above. Consider the Kb values of the methyl amines given above. The increase in Kb from methylamine to dimethylamine may be attributed to +I effect; however, there is a decrease from dimethylamine to trimethyl amine due to the predominance of steric hindrance offered by the three methyl groups to the approaching Brönsted acid.

Ions of compound

Kb

Ammonia NH3

1.8·10−5 M

Aniline C6H5NH2

3.8·10−10 M

4-Methylaniline 4-CH3C6H4NH2

1.2·10−9 M

2-Nitroaniline

1.5·10−15 M

3-Nitroaniline

2.8·10−13 M

4-Nitroaniline

9.5·10−14 M

-M effect of aromatic ring delocalises the lone pair of electrons on nitrogen into the ring, resulting in decreased basicity. Substituents on the aromatic ring, and their positions relative to the amine group may also considerably alter basicity as seen above.

  • The degree of solvation of protonated amines:

Ions of compound

Maximum number of H-bond

NH4+

4 Very Soluble in H2O

RNH3+

3

R2NH2+

2

R3NH+

1 Least Soluble in H2O

In sterically hindered amines, as in the case of trimethylamine, the protonated form is not well-solvated. For this reason the parent amine is less basic than expected. In the case of aprotic polar solvents (like DMSO and DMF), wherein the extent of solvation is not as high as in protic polar solvents (like water and methanol), the basicity of amines is almost solely governed by the electronic factors within the molecule.

[edit] Synthesis

[edit] Alkylation

The most industrially significant amines are prepared from ammonia by alkylation with alcohols:

ROH + NH3 → RNH2 + H2O

These reactions require catalysts, specialized apparatus, and additional purification measures since the selectivity can be problematic. Treatment of Haloalkanes with amines give the corresponding alkyl-substituted amine, with the release of a halogen acid, which in turn reacts with the amine product or precursor:

RX + 2 R'NH2 → RR'NH + [RR'NH2]X

Such reactions, which are most useful for alkyl iodides and bromides, are rarely employed because the degree of alkylation is difficult to control.[3]

[edit] Reductive routes

Via the process of hydrogenation, nitriles are reduced to amines using hydrogen in the presence of a nickel catalyst. Reactions are sensitive acidic or alkaline conditions, which can cause hydrolysis of -CN group. LiAlH4 is more commonly employed for the reduction of nitriles on the laboratory scale. Similarly, LiAlH4 reduces amides to amines. Many amines are produced from aldehydes and ketones via reductive amination, which can use either catalytic hydrogenation or stoichiometric reagents.

Aniline and its derivatives are prepared by reduction of the nitroaromatics. In industry, hydrogen is the preferred reductant, whereas in the laboratory, tin and iron are often employed.

[edit] Specialized methods

Many laboratory methods exist for the preparation of amines, many of these methods being rather specialized.

Reaction name

Substrate

Comment

Gabriel synthesis

organohalide

reagent: potassium phthalimide

Staudinger reduction

Azide

This reaction also takes place with a reducing agent such as lithium aluminium hydride.

Schmidt reaction

carboxylic acid

Aza-Baylis–Hillman reaction

imine

Synthesis of allylic amines

Hofmann degradation

amide

This reaction is valid for preparation of primary amines only. Gives good yields of primary amines uncontaminated with other amines.

Hofmann Elimination

Quaternary ammonium salt

upon treatment with strong base

Amide reduction

amides

Nitrile reduction

nitriles

Reduction of nitro compounds

nitro compounds

can be accomplished with elemental zinc, tin or iron with an acid.

Amine alkylation

haloalkane

Delepine reaction

organohalide

reagent hexamine

Buchwald-Hartwig reaction

aryl halide

specific for aryl amines

Menshutkin reaction

tertiary amine

reaction product a quaternary ammonium cation

hydroamination

alkenes and alkynes

Hofmann-Löffler reaction

haloamine

[edit] Reactions

[edit] Alkylation, acylation, and sulfonation

The dominant reactivity of amines is their nucleophilicity.[4] Most primary amines are good ligands for metal ions to give coordination complexes. Amines are alkylated by alkyl halides. Acyl chlorides and acid anhydrides react with primary and secondary amines to form amides (the "Schotten-Baumann reaction").

Similarly, with sulfonyl chlorides, one obtains sulfonamides. This transformation, known as the Hinsberg reaction, is a chemical test for the presence of amines.

Because amines are basic, they neutralize acids to form the corresponding ammonium salts R3NH+. When formed from carboxylic acids and primary and secondary amines, these salts thermally dehydrate to form the corresponding amides.

[edit] Diazotization

Amines react with nitrous acid to give diazonium salts. The most important members are derivatives of aromatic amines such as aniline ("phenylamine") (Ar = aryl or naphthyl):

ArNH2 + HNO2 + HX → ArN2+X- + 2 H2O

Anilines and naphthylamines form more stable diazonium salts, which can be isolated in the crystalline form.[5] Diazonium salts undergo a variety of useful transformations involving replacement of the N2 group with anions. For example, cuprous cyanide gives the corresponding nitriles:

ArN2+X- + Y- → ArY + N2 + X-

Aryldiazonium couple with electron-rich aromatic compounds such as a phenol to form azo compounds, which are widely used as dyes. The alkyl diazonium salts are of little synthetic importance because the diazonium derivatives are too unstable.

[edit] Conversion to imines

Imine formation is an important reaction. Primary amines react with ketones and aldehydes to form imines. In the case of formaldehyde (R' = H), these products typically exist as cyclic trimers.

RNH2 + R'2C=O → R'2C=NR + H2O

Reduction of these imines gives secondary amines:

R'2C=NR + H2 → R'2CH-NHR

Similarly, secondary amines react with ketones and aldehydes to form enamines:

R2NH + R'(R"CH2)C=O → R"CH=C(NR2)R' + H2O

[edit] Overview

An overview of the reactions of amine is given below:

Reaction name

Reaction product

Comment

Amine alkylation

amines

degree of substitution increases

Schotten-Baumann reaction

amides

Reagents: acyl chlorides, acid anhydrides

Hinsberg reaction

sulfonamides

Reagents: sulfonyl chlorides

Amine-carbonyl condensation

imines

Organic oxidation

nitroso compounds

Reagent: peroxymonosulfuric acid

Organic oxidation

diazonium salt

Reagent: nitrous acid

Zincke reaction

Zincke aldehyde

reagent pyridinium salts , with primary and secondary amines

Emde degradation

tertiary amine

reduction of quaternary ammonium cations

Hofmann-Martius rearrangement

aryl substituted anilines

Von Braun reaction

Organocyanamide

By cleavage (tertiary amines only) with cyanogen bromide

[edit] Biological activity

Amines are ubiquitous in biology. The breakdown of amino acids releases amines, famously in the case of decaying fish which smell of trimethylamine. Many neurotransmitters are amines, including epinephrine, norepinephrine, dopamine, serotonin, and histamine. Protonated amino groups (-NH3+) are the most common positively charged moieties in proteins, specifically in the amino acid lysine.[6] The anionic polymer DNA is typically bound to various amine-rich proteins.[7] Additionally, the charged ammonium centers on lysine form salt bridges with carboxylate groups of other amino acids in polypeptides, which influences the three-dimensional structures of proteins.[8]

[edit] Application of amines

[edit] Dyes

Primary aromatic amines are used as a starting material for the manufacture of azo dyes. It reacts with nitric(III) acid to form diazonium salt, which can undergo coupling reaction to form azo compound. As azo-compounds are highly coloured, they are widely used in dyeing industries, such as:

[edit] Drugs

Many drugs are designed to mimic or to interfere with the action of natural amine neurotransmitters, exemplified by the amine drugs:

[edit] Gas treatment

  • Aqueous monoethanolamine (MEA), diglycolamine (DGA), diethanolamine (DEA), diisopropanolamine (DIPA) and methyldiethanolamine (MDEA) are widely used industrially for removing carbon dioxide (CO2) and hydrogen sulfide (H2S) from natural gas streams and refinery process streams. They may also be used to remove CO2 from combustion gases / flue gases and may have potential for abatement of greenhouse gases.

[edit] Safety

Low molecular weight amines are toxic, and some are easily absorbed through the skin. Many higher molecular weight amines are highly active biologically.

[edit] External links

[edit] See also

[edit] References

1.      ^ McMurry, John E. (1992), Organic Chemistry (3rd ed.), Belmont: Wadsworth, ISBN 0-534-16218-5 

2.      ^ Lide, D. R., ed. (2005), CRC Handbook of Chemistry and Physics (86th ed.), Boca Raton (FL): CRC Press, ISBN 0-8493-0486-5 

3.      ^ Karsten Eller, Erhard Henkes, Roland Rossbacher, Hartmut Höke "Amines, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a02_001

4.      ^ March, Jerry (1992), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (4th ed.), New York: Wiley, ISBN 0-471-60180-2 

5.      ^ A. N. Nesmajanow (1943), "β-Naphthylmercuric chloride", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv2p0432 ; Coll. Vol. 2: 432 

6.      ^ Miguel A. Andrade, Sean I. O'Donoghue, Burkhard Rost, Adaptation of protein surfaces to subcellular location, Journal of Molecular Biology, Volume 276, Issue 2, 20 February 1998, Pages 517-525, ISSN 0022-2836

7.      ^ Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.

8.      ^ Dominant forces in protein folding, Ken A. Dill, Biochemistry 1990 29 (31), 7133-7155

Retrieved from "http://en.wikipedia.org/wiki/Amine"

Categories: Amines

 

 

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 Elemental Analysis

 Introduction: 
  More mixed resolution Kybat organic: organic chemist in identifying compounds less than a pure object, but will deal mainly with the object byproducts and raw materials are mixed. However, despite the new separation methods, especially chromatographic methods to isolate pure compounds from the past is easier with however, should not ignore the importance of classical methods. 
General based methods often separate organic mixtures'm going to use the polarity that exists in the components of a mixture or it occurs. This difference in nearly all separation techniques including distillation - crystallization - the extraction and chromatography work is produced.'s largest polarity that makes it easier for the separation of the difference in Qtybt salts and non-polar organic materials there. Jzaz Whenever one or more salts of a mixture to be distinguished easily can be related to the components to help extraction or distillation completely non-polar component was isolated. 
Classical organic qualitative analysis method: 
The analysis includes six basic steps that the pudding is in the following: 
Preliminary experiments on physical and chemical properties 
  Elemental analysis 

 related to the solubility experiments 
experiments related groupings (different factors other than activity Asydv opening reactions) 
preparation is derived
This method is very valuable. The method can be an organic compound commonly known mineral composition than the one diagnosed with more confidence.
Elemental analysis

. Na Sr Mvjvddrtrkybat conventional organic hydrogen Vaksyzhn Ben is deaf sometimes other elements such as nitrogen - sulfur - oxygen and halogen Hahm chemists are found. 
. For oxygen, a simple test, there Ndardv other elements transplanted Kvalansy connecting Hstndv Therefore experiments ionic conventional straight answers do not. But if the object of organic unknowns with sodium molten melt in Agsr cases such compound is the N and S and X to the ions CN and S and CNS and X becomes . After excess sodium was destroyed exactly the aqueous solution containing the normal method of mineral analysis Yvnhast are. a more complete explanation in this case is that it outlines the following.
Carbon-hydrogen Vaksyzhn 
  To prove the existence of carbon and hydrogen dry powder samples Raba Cu (II) oxide, which has led to heated carbon dioxide and water are. . Carbon present in the sample gas passing to generated from within the rim or calcium hydroxide solution is not clear that this case is the corresponding carbonate deposits. . Hydrogen can be caused by drops of water condensed on the upper tube was diagnosed.  No qualitative test for the existence of oxygen in organic compounds, there is no quantitative analysis to determine the oxygen must get done. If this method if the total percentage of all the elements constituting the composition to less than 100 are related to the Sdaksyzhn. 
Nitrogen, sulfur and halogens 
Qualitative diagnosis of these elements in organic compounds, inorganic compounds the problem is in the balance.  Because most organic compounds in solution mode Drab considerable amounts are not ionized. Since the qualitative analysis experiments are based on ionic reactions they can not be directly applied to organic compounds. For example sodium chloride or sodium bromide with aqueous solution of silver nitrate to a significant amount of silver halide precipitation should occur while the carbon tetrachloride - benzene and often Halydhay Brvmv organic aqueous solution when reacted with silver silver halide deposition Nyrat shall not create them because the amount of halide ion solution is not in production.
: In this case it is necessary for qualitative detection of N first elements - sulfur - and the halogen compound to be ionized into self. One of the most common method of doing this conversion Hajht melting sodium metal samples is done with the elements mentioned the compound sodium cyanide - Sodium Svlfydv sodium halide are converted. The anion can be obtained by routine tests can identify minerals. reactivity with the molten sodium is as follows: 

In cases where sodium enough applied not matter desired with sulfur Vnytrvzhn (both) is sometimes separated well is not conducted Wayne two elements as composition NaSCN are displayed. To identify the composition of Klrv formic 10 percent is used.

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In compounds containing carbonyl groups are operating, if the carbonyl groups with hydrogen atoms or alkyl groups is substituted, aldehyde (RCHO) or ketone (RCOR) are called. Chemical compounds in the carbonyl functional group is chemistry. The compounds identified by the characteristic functional group carbonyl reactions are possible. 

 

آلدهید و کتون



Aldehydes and ketones is to identify the different tests, there can be of them test 2and 4 - nitro phenyl hydrazine in the , chromic acid test, test Ydvfrm, Talnz test test test Fuchsin Benedict noted.



Test 2 and 4 -  nitro phenyl hydrazine:



Aldehydes and ketones with the reagent 2 and 4 - nitro phenyl hydrazine formation of the deposits are orange to red. The test for the detection of aldehyde and ketone other compounds are used. If the aldehyde or ketone Law to be tested if the red color of the precipitation trends will find.
تست 2 و 4 – دی نیترو فنیل هیدرازین


In the figure below represents the reaction between a ketone and 2 and 4 - nitro phenyl hydrazine reagent will see:


Method of preparation reagent 2 and 4 - nitro phenyl hydrazine:
1 g 2 and 4 - nitro phenyl hydrazine in 5 ml of concentrated sulfuric acid solution and the solution cautiously to 7 ml water and 25 ml add 95 percent ethanol. , it separated from the solids unresolved.

Methods to identify:
Two or three drops of liquid X (05 / 0 g of solid) in 2 mL of ethanol solution and drops of reagent 2 and 4 - nitro phenyl hydrazine add to it. Deposits formed on the orange to red because there is an aldehyde or ketone. Presence of conjugated double bond with the carbonyl group causes sediment to be red.

Talnz test or Tvlns:
Talnz test (Tvlns) Another practice that is used to detect aldehydes of ketones are used. Talnz reagent react with aldehydes (Tvlns) produced a silver mirror on the wall to test tubes.

Reaction in the form below to test Talnz (Tvlns) will see:
واکنش مربوط به تست تالنز
 
Reagent preparation method Talnz (Tvlns):

A solution of silver nitrate dissolving 3 g in 30 ml of water is available in soda solution and solution B is 10 percent. Reagent must be used immediately after preparation. Reagent for the preparation Talnz (Tvlns), one ml of solution A with one ml of solution B mix. Silver oxide deposits are formed. Then concentrated ammonia solution drop by drop to add to silver oxide deposits is resolved. Now reagent is ready for testing.

In the following reactions to prepare reagent Talnz (Tvlns) will see:
تهیه معرف تالنز

Note: Reactive Talnz (Tvlns) should be prepared and consumed during the remainder will be excreted within laundering. If the solution is maintained, the possibility of forming explosive Fulminating silver deposits there. This precipitated a mixture of silver nitride (Ag3N) and silver AZyd (AgN3) is.

Methods:

5 0 / ml reagent Talnz (Tvlns) to 3 drops or 1 / 0 grams of Article X to add. Forming a silver mirror or black deposits indicate positive are tested. If did not perform reaction in normal temperature,heat in a little hot water temperature .

Note 1: If the test tube is not clean, silver, silver mirror to the wall of test tube is not formed, and to deposit or suspension appeared to be black.

Note 2: Some simple Ketons like acetone and methyl ethyl ketone also give positive response to the test.

Fuchsin Test:

in Fuchsin test  reagent should not be heated and  solution should not be alkaline. During tests on the unknowns, it is best seen as an known aldehyde used.

 

 Fuchsin reagent preparation method or indicator:
5 / 0 grams of pure Fuchsin (rosaniline hydrochloride) in 500 ml distilled water solution and the solution can smooth; 500 ml distilled water with sulfur dioxide, saturate, with a fully mixed solution of Fuchsin overnight and had to leave. This method, produces colorless reagent.


Fuchsin reagent in the form of infrastructure or Rvzanylyn hydrochloride can see:

فوشین
Methods:

2 ml of reagent Fuchsin - aldehyde in a test tube and poured a drop of aldehyde tested to add. Color produced in minutes See. (Eg willing to violet purple Bvtanal within 3 to 4 minutes to appear.) Reminded that the referral should not be heated.


Benedict test:

Benedict reagent, a reagent called by name an American chemist (Stanley Rossiter Benedict) is. Aliphatic Ldhydhay to identify (non-aromatic) no sulfur and alpha-hydroxy ketone is used. In response following an aldehyde and an alpha hydroxy ketone with Benedict reagent see:

بندیکت


 

 

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IDENTIFY OF ALKANS,ALKENS,ALKYNS,ALYFATIK HALYDS,AROMATIK HYDROCARONS & CARBON HYDRATSتصویر

ALKENS functional group, links _ double carbon carbon. Therefore, to identify an unknown compound Alkens, must be shown that the typical reaction _ carbon-carbon double transplant does. Due to the number of such reactions, this may seem an easy task.


If possible, identify a reaction as a test, we choose to do quickly and easily be modified to be observational and lead.we choose a few minutes to test time and require multiple test tube test, in which color is formed or broken, or bubbles rising Gar, or sedimentary formation or be resolved.


The best way to identify alkens.
experience is the best way to identify ALKENS, the decolorization properties in carbon tetrachloride solution of bromine in the cold solution, permanganate is diluted. Doing both tests is easy. In one, red is destroyed and replaced by another purple to brown manganese dioxide does.


Error and uncertainty in identifying
After choosing the best tests to identify stammerer, to examine other questions. Bromine in carbon tetrachloride to an unknown combination of organic and suppose we add the red color is destroyed. Truly this was the phenomenon of what could result? One can only say that we brominated material is unknown. A course may be aLkan.
Knowing that a certain type of combination with a particular and specific reagent to react spontaneously is not enough. But must also know which other compounds react with this reagent? In this case, the unknown compound may also be a Lkyn. Any other combination is also possible to react rapidly with bromine substitution will, be. However, in this case, hydrogen bromide gas will evaporate the simplest way to detect it, blowing into the test tube and observed cloud mass formed, is.

Also, decolorization permanganate stammerer Nmyrsand be combined to prove, but there just kind of drop oxide functional group shows with permanganate. Combined test may be a stammerer, but likely Lkyn aldehyde or any other compound that oxidizes easily, also there. May even contain some combination that is conducive oxide impurities. For example, stammerer in such circumstances are not oxidized, but often, the oxide impurities that are conducive. For example, alcohols, such circumstances are not oxidized, but often that impurities are oxidized. To fix this ambiguity, can be two or three drops of decolorization reagent ensuring.

With a detection test, can rarely be proved unknown composition. Probability of a test can only reduce, so that additional tests, the final decision is possible. Consequently, bromine or permanganate test for detection of Lkan stammerer or stammerer of alkyl halide or alcohol stammerer enough.

 alkens a great bunch of hydrocarbons that includes the unsaturated hydrocarbons (unsaturated) Mvsvmnd. Total hydrogenated compounds, carbon is less than Lknhay time. Stammerer may separate one or more double bond and far apart or have married.



 experience is the best way to identify a stammerer, the decolorization properties in carbon tetrachloride solution of bromine in the cold solution, permanganate is diluted Khnsay. Doing both tests is easy. In one, red is destroyed and replaced by another purple to brown manganese dioxide is
 

   
 
A) bromine solution in carbon tetrachloride: incremental reaction to go on double and triple bond takes place
Bromine test for alkenes.

METHOD 

0.1 g (0.2 mg Lytrmay) Aznmvnh review Lytrttra chloride to 2 mm carbon add 5% bromine solution in Wake Ttraklrydkrbn drop (with shaking) to add color to go until it is stabilized.

Be taking over from two drops of bromine solution represents the response is an increase or Substituted and colorless with Azmhlvl drops from two to go over with the release if Gazbrmydhydrvzhn Nbashdnshan donor response is increasing. Almost all compounds or Lkyn Sakhtaralkn Darndbh easily brominated by it are colorless, but this result should also Tayydshvd permanganate test







2) Test permanganate ion (Bayer test)

Methods: 30-25 mg of the compound Drab or alcohol-acetone solution and then drop 1% watery solution of potassium permanganate and poured a good stir. If more than one drop of permanganate was used to combine or unsaturated or Aksydshvndh easily. Agrnmvnh to test both the first and second incremental positive response to the reaction I was done and the desired compound can be stammerer or Lkyn.





Alkyne


Physical peropertis

 Generally, physical properties similar Lkanhast stammerer. Stammerer in nonpolar solvents such as ether, chloroform and methane Dyklrv solution but are insoluble in water and also are lighter than water. Stammerer boiling point with increasing the number of carbon increases. Except for small Lknhay, boiling point increases stammerer a carbon atom per 20 to 30 degrees Celsius increase. Like Lkanha, being Shakhhdar stammerer boiling point is reduced.

Qtbytr are of little stammerer Lkanha low polarity of the character of the electron and electron week group is created. When the stammerer, groups with more power is being induced, dipole moment slightly increases.

 

Chemical propertise


 Generally, two types of reaction is achieved in the alkens. The first group are those that are performed in the link and therefore π π transplant is destroyed and new bonds are formed. Latter reaction, the reactions of other solutions that are associated with a particular double bond have happen. Like alkyl groups, or other factors that are connected Krbnhay sp2.


  
Complication
Decolorization permanganate stammerer Nmyrsand being combined to prove, but there just kind of drop oxide functional group shows with permanganate. Combined test may be a stammerer, but likely Lkyn aldehyde or any other compound that oxidizes easily, there is also
most aldehydes give a positive test
formic acid and its esters give a positive test
phenols and aryl amines give a positive test
  
carbon tetrachloride MSDS
 

Aromatic hydrocarbons:
Friedel Krafts test:
Method: 1 / 0 or 3 g of solid sample / ml Azmay 0 items dry and clean a test tube poured And it can add 2 ml chloroform. The size of the head on the wall of aluminum chloride Aspatvl test tube fold. Wall color is a sign of positive test.
Ann Vhmvlvg·hay benzene: Orange Red
Ftantrn: Purple
Anthracene: Green
 

 
Positive test showing red color for 1,2,3-trimethylbenzene
.
Complication
Aromatic esters - ketone is more oxygen containing amine is Vtrkybat Vnytrvzhn may also be blue or green to create.
In doing this test should also use the reagent and how to test accuracy. If ALCL3 humidity should become aluminum hydroxide are other ALCL3 for reaction Friedel Craft Asfadh not enmity acres the heat do to the aluminum oxide is converted. In performing the test water should not be entered if the water logged into the system problems make them

 

Compound MSD

 Safety data for aluminium chloride, anhydrous

 

 

Carbohydrates (sugars or carbohydrates) are a type of biological molecule that is chemically carbohydrates Vqndha them: the Plyhydrvksyaldyyd or Plyhydrvksyktvn know. Carbohydrates from carbon atoms, hydrogen and oxygen are


                 

                        

Structure of lactose (milk sugar).
 
Krbv Hydratha compounds that are soluble in water but can not be solved in ether S2 compounds are therefore only due to the polar groups like the only polar compounds are dissolved in water to identify the carbohydrates of the following tests are used:

 
 
1) Test Mvlysh: concentrated sulfuric acid hydrolysis caused by fitting glycoside, will create Mvnvsakaryd. Mvnvsakaryd generated loses its water and is converted into furfural and its derivatives. Then combined with alpha Nftl create complex color purple.
 
Method: 1 ml of sugar solution poured into a test tube, two drops of the solution and add alpha Nftl stir well. Sure to 3 ml of concentrated sulfuric acid tube walls add. Slowly add the acid to the solution within the tube and did not below, a phase (part) is formed.





a negative test (left) and a positive test (right
 
 Safety data for 2-naphthol
 
 
2) Barfvd Test: This test is to detect polysaccharide from January Saka me to the Reed used a red sediment is obtained which is due to copper oxide.
If the test sugars reclamation occurs in weak acid environments, and duration of heating is controlled, because only mono polysaccharide produced strong restore power to the test are positive.

 RHCO+2CU+++2H2O=RHOCO+CU2O+4H+


 
Methods: A Barfvd ml solution in test tube and poured into the 2 ml solution add 2% sugar. Test tubes in boiling water bath place. If the red deposits were formed within two minutes, is a polysaccharide sugar test mono. Disaccharide should be longer (eg 10 minutes) to sediment red Jvshanyd be created.
 


a negative test (left) and a positive test (right)
 

3)Test Benedict:

Benedict reagent, a reagent called by name an American chemist (Stanley Rossiter Benedict) is. Aliphatic Ldhydhay to identify (non-aromatic) no sulfur and alpha-hydroxy ketone is used.

Benedict reagent preparation methods:

To a solution of 2 / 0 g samples in 5 ml distilled Lytrab Asydklrydryk thick add 2 drops of solution to boil for one minute Zhs of the cold solution you can then neutralized by a diluted earnings ml reagent Benedict Ramlahzh Tghyyrrng can add.

Methods:

To a solution of 2 / 0 g sample in 5 ml distilled Lytrab Asydklrydryk thick add 2 drops of solution to boil for one minute Zhs of the cold solution you can then neutralized by a diluted earnings ml reagent Benedict Ramlahzh Tghyyrrng can add.

Benedict test

 Safety data for hydrochloric acid

 

Aliphatic Halyd:


Silver Nitrate in Ethanol Test1)

 

Procedure


Place approximately 0.25 mL of each compound into a test tube. Add 2 mL of a 1% ethanolic silver nitrate solution to the material in each test tube, noting the time of addition. After the addition, shake the test tube well to ensure adequate mixing of the compound and the solution. Record the time required for any precipitates to form. If no precipitates are seen after 5 minutes, heat the solution on the steam bath for approximately 5 minutes. Note whether a precipitate forms in the test tube. Continue slow reactions for up to 45 minutes at room temperature.

 

Complications
 

Carboxylic acids have been known to react in this test, giving false positives

 

Beilstein Test(۲

Procedure

 Heat the tip of a copper wire in a burner flame until there is no further coloration of the flame. Let the wire cool slightly, then dip it into the unknown (solid or liquid" and again, heat it in the flame. A green flash is indicative of chlorine, bromine, and iodine; fluorine is not detected because copper fluoride is not volatile. The Beilstein test is very sensitive, thus halogen-containing impurities may give misleading results.

 

+ نوشته شده در  دوشنبه دوازدهم اردیبهشت 1390ساعت 13:50  توسط ساناز رضائی معصومه سرافراز  | 

تست 2 و 4 – دی نیترو فنیل هیدرازین

+ نوشته شده در  دوشنبه دوازدهم اردیبهشت 1390ساعت 12:39  توسط ساناز رضائی معصومه سرافراز  | 

At first it is better to existing differences between the alcohols, phenols and a Anvl be pointed  . Compounds that are alcohols hydroxyl groups attached to sp2 carbon atoms are saturated, while phenols with hydroxyl groups are attached to aromatic rings.  : HOH با ROH  Ar-OH . Both can be derived from water as considered in which a hydrogenated water by a group of organic change is: HOH or ROH compared with Ar-OH.  Note that is Anvl compounds hydroxyl group are attached to a vinyl carbon. Due to the different chemical compounds in most cases to be discussed separately.
: Figure infrastructure; alcohol, phenol and Anvl will see:

: Alcohols identified:
. Alcohols are neutral compounds  . Other neutral compounds; aldehyde, the ketone and ester are. معمولاً . Usually to test alcohol and ester 2 and 4 - nitro phenyl hydrazine in the Persian month Dey do not respond, but the resulting aldehyde and ketone test is positive. استر ها  . Vaknshgrhay ester with acetyl chloride or Lukas reagent not reactive, but the reaction of alcohols with this reagent are doing both. . This is because the ease of identifying them is alcohol. . Alcohol type I and II are easily oxidized, but the third type of esters and alcohols are not oxidized.   Conducted two experiments with Lucas and chromic acids, alcohols can be kind of first, second and third detected. 
  . To identify alcohols, there are different tests that can test them; detect active hydrogen or sodium metal testing, test hex Nytratv ammonium cerium (IV) ammonium nitrate or Sryk testing, the diagnosis of alcoholic OH or being tested by Ester Steele chloride, chromic acid test or Jones, xanthan formation, Lucas test, test, N - Brmv Aymyd succinate (NBS) and the acid test Prydyk noted.
: Active detection of hydrogen or sodium metal test: 
Including the basic properties of hydroxyl groups make hydrogen bonds and hydrogen chemical exchange.  . Metallic hydrogen (especially samples that are fresh cut) readily reacts with hydroxyl groups are hydrogen.

 . Note: functional groups attached to nitrogen, hydrogen and sulfur, can also produce hydrogen gas drawn.

 . Acetylene compounds also reacts with sodium are. ،  But leaving hydrogen gas is not observed, because as fast as the hydrogen is produced with the same velocity hydrogen reacts with double bonds will increase.
: Test Methods for identifying alcohol sodium metal:
. About 5 0 / ml of the unknown sample in a test tube and put a piece of sodium to the grain size of the cast. . If removal of hydrogen gas can be proved the presence of active hydrogen. 
  . NOTE: moisture present in the composition of hydrogen gas is led out.

  NH4)2Ce(NO3)6): Ammonium nitrate test Sryk NH4) 2Ce (NO3) 6): 
  . Sryk reagent with ammonium nitrate compounds containing alcoholic hydroxyl groups, are a red complex forms.  . Answer test for the type of alcohols first, second and third are less than 10 carbon, is positive.   . All types of glycol, the poly L, the carbohydrates, hydroxy acids, hydroxy aldehydes and hydroxy ketones, the positive response to this test and they produce a red solution.

 . Must be careful, the red-complex formation, an intermediate in the oxidation of alcohols is by representing the above.  (Ce(lll است . Part II reactions include loss of color and form a colorless complex (Ce (lll is.

 : Ammonium nitrate reagent preparation method Sryk: 
Sryk 200 g ammonium nitrate in 500 ml of 2N nitric acid solution to a yellow solution 
. Obtained. 
Methods: 
One ml of the above reagent in a test tube and poured about 5 to 6 drops of unknowns on the add. . Formation of red because of the alcoholic hydroxyl group is there. 
. Note: The phenols in red do not make clear, and when they check in Dioxane solution to brown or black color products are oxidized. 
. Note: The time required for the loss of red color on the first type of alcohol one to five hours, the second type of alcohols 3 to 12 hours and the third type of alcohols, more than two days.
. Note: Aliphatic amines by forming white deposits are Sryk hydroxide.
: OH detection by alcohol to ester (acetyl chloride test):
. Acid chloride in the reaction of alcohols, to produce polyester.   . Acetyl chloride in response to acetate esters.   . Usually the reaction is exothermic and heat is easily detectable. 
  . 5 0 / ml of compound X in a test tube to the 5 0 / ml acetyl chloride to add.  . About 3 to 4 minutes, stir the solution.  5  . Then about 2 ml of water solution added drop by drop sodium bicarbonate solution, add 5 percent.   . Ester formation due to the pleasant smell is there reason alcohol functional group is combined.
: Acetyl chloride following the reaction with alcohol you will see:

Note: As with phenol alcohol reacts with acetyl chloride are.
: Test chromic acid (Jones reagent): 
  . The reaction to detect and diagnose all types of alcohol alcohol first and second third type is based on reduction of chromium (VI) yellow - orange, the chromium (III) is green. . Alcohol is oxidized by this reagent. . Reagent color change from orange to green as a positive response to the experiment.  . The first and second alcohols by this reagent, respectively, to carboxylic acids and ketones are converted.

 . Alcohol should be noted that the first type of aldehyde oxidation first and then are converted to carboxylic acid, but the second type of alcohol that is produced ketones, oxidation stops. 
. Note: The first and second type of alcohol test chromic acid (Jones reagent) are positive responses, but the third type of alcohol test do not respond.
. Note: aldehyde also to test chromic acid (Jones reagent) give a positive response. 
: Methods: 
  . In a test tube about 1 ml acetone and poured about 3 to 4 drops of the desired alcohol in it can solve.  . Then just a drop of chromic acid (Jones reagent) to add.  . Rapid formation of the green suspension - because the water has tested positive.
: Xanthan formation test: 
. The test to detect type of alcohol first, second and third time is.
ر : Methods:
. In a test tube a small piece of the potash and put about 5 / 0 X ml of alcohol to add.   . KOH with stirring in alcohol can solve.  . If necessary you can also use heat. . After cooling the solution in the Persian month Dey approximately 1 ml ethyl ether added to it and drop it onto carbon disulfide.
. Alcohol Type III: This test is not responding.
. Alcohol Type II: After about five seconds of yellow deposits appear to xanthan.
CS2 . The first type of alcohol: a fast and sediment entering the CS2 to produce. 
Note: Only consider sediment is formed, producing a brown color because the sediment is created. 
: Lucas test:
. Lucas test to detect the third type of alcohol, and benzyl alcohol Lyly type is the first and second.
. This test is based on the reaction of alcohol with a mixture of hydrochloric acid and zinc chloride (reagent Lucas) that the alkyl chloride product as a layer that is insoluble. 
   . The first type of alcohols at room temperature with Lucas reagent, and therefore do not react . The second type of alcohol test Lukas respond slowly, so that this test is considered negative about them. . But the third type of alcohol, and Lylyk Bnzylyk participate immediately in response. 
   . This reaction mechanism point of view they are SN1 reactions, which form ion goes.  : In the figure below represents the reaction mechanism Lucas III to a type of alcohol you will see:

 : Lyly alcohol reaction with a reagent Lucas:

 : Benzyl alcohol react with a reagent Lucas:

: Lucas reagent preparation methods:
Amount of 136 grams (1 mole) ZnCl2 dried at 105 grams (1 mol) concentrated hydrochloric acid solution on.
: Methods: 
. 5 / 0 ml of the desired alcohol, 1 ml reagent Lucas added it immediately in water bath at a temperature of 60 degrees Celsius place. . The third type of alcohols, benzyl and Lyly shortly after, first opaque and ultimately produce the two phases are separated.
. Note: Because Lucas test appearing alkyl chloride as the second liquid phase depends on the result only in this referral Alklhayy are solved, can be used. . Therefore, this test alcohol-related single-agent that are less than six carbon atoms. 
: Test N - Brmv Aymyd succinate (NBS) to identify alcohols: 
N – : Infrastructure in the form N - Brmv Aymyd succinate (NBS) will see:

 (NBS) : Methods Identification of alcohol by (NBS): 
  . In a clean test tube about 1 ml of alcohol and poured into the desired size of the combined tip Aspatvl N - Brmv succinate Aymyd it and add it in the water bath temperature 75 to 80 degrees Celsius can. 
. The first type of alcohol: about 1 minute or more for the loss of color is needed.
. Alcohol Type III: a quick and immediate positive response to this test.
(HIO4) : Prydyk acid test (HIO4): 
(HIO4) ، (Vicinal Diols). Prydyk acid test (HIO4), to identify factors OH alcohols with adjacent or nearby El Persian month Dey (Vicinal Diols) is. 
: Prydyk acid reagent preparation methods: 
. 5 / 0 g para Prydyk acid (H5IO6) in 100 ml distilled water, dissolve. 
(H (HIO4) را : Para Prydyk acid in the form of infrastructure (H5IO6) and Prydyk acid (HIO4) will see:

 : Methods:
2. 2 ml Prydyk acid (HIO4) in a test tube and poured a drop it (no more) and add concentrated nitric acid, stir well . Then a drop of sample tested and added to the mixture for 15 to 20 seconds Shake. . Now a solution of silver nitrate drops to two juicy 5 percent to add the contents into test tubes. (AgIO3)  . Silver white sediment formed Ydat (AgIO3) indicate factors is adjacent OH. or brown formed because of the test result is negative. 
   . Note: If the test compound is insoluble in water, can be used to facilitate the reaction of Dioxane solvent used. 
  : Prydyk acid reaction in the form below (HIO4) with an alcohol (Dec L) will see:

  : Preparation of solid derivatives for alcohols: 
. Derivatives on alcohols that are common include: phenyl urethane, urethane Nftyl alpha, 2 and 5 - Persian month Dey nitro benzoate and 3 - nitro phthalate. 
: Method of preparation derived urethane Nftyl alpha (α - Nftyl urethane): 
. One gram of alcohol or phenol without water poured into a test tube and 5 / 0 ml phenyl iso CNN to add.  . If the phenol compound is unknown, should react with two or three drops of pyridine or anhydrous ethanol amine will catalyze  . If the reaction to his own failed, the solution for 5 minutes to warm on the steam bath.  . Then the desired solution containing a human ice, cold, and women with the human wall of glass to scratch, and get through this Krystalyz·h crystallization is accelerated. g it with 5 ml of petroleum ether or carbon tetrachloride can recrystallization.
Alcohol in the following reaction with phenyl iso CNN and preparing urethane derivative of alpha Nftyl will see:

 : Method of preparation derived from 3 and 5 - nitro benzoate Persian month Dey: 5. About 5 / g 0, 3 and 5 - nitro-benzoyl chloride in the Persian month Dey with 2 ml of the unknown substance (alcohol) in a test tube and mix gently boil for about 5 minutes.  . Then 10 ml distilled water added to the solution in ice bath, cool to give a deposition. 10   . And smooth deposits with 10 ml of 2 percent solution of sodium carbonate wash.   . Recrystallization with 5 to 10 ml of ethanol and water solution can do.
: Alcohol reactions in Figure 3 and 5 - nitro benzoyl chloride and production of the Persian month Dey derivatives 3 and 5 - nitro benzoate Persian month Dey will see:

 : Method of preparation derived from 3 - nitro-phthalate: 
. Mixture of 4 / 0 g, 3 - nitro Ftalyk anhydride and 5 / 0 ml of alcohol (if the temperature of the weld is less than 150 degrees Celsius.) In a very small balloon attached to the condenser (condenser) to gently boil.  . After the liquid was mixed, heated to 5 to 10 minutes longer continue. . The mixture cooled diluted with 5 ml of water and heat until boiling can. . If dissolution is not complete, 5 to 10 ml of hot water can add.  . Cold crystallization solution for you.  . If oily substance was formed, in order to form crystals should stay one night.  . The product once or twice with hot water can recrystallization. 
  : In the following three reactions - Ftalyk anhydride with alcohol and nitro derivatives produced 3 - nitro phthalate can see: 
: Phthalate derivatives:










+ نوشته شده در  یکشنبه چهارم اردیبهشت 1390ساعت 12:34  توسط ساناز رضائی معصومه سرافراز  | 

Tests for Alcohols

Jones Oxidation for Primary and Secondary Alcohols

Lucas Test for Secondary and Tertiary Alcohols


Jones Oxidation for Primary and Secondary Alcohols

Alcohol

Standards
1-Butanol, 2-Butanol, t-Butyl alcohol

Procedure
Dissolve 10 mg or 2 drops of the unknown in 1 mL of pure acetone in a test tube and add to the solution 1 small drop of Jones reagent (chronic acid in sulfuric acid). A positive test is marked by the formation of a green color within 15 seconds upon addition of the orange-yellow reagent to a primary or secondary alcohol. Aldehydes also give a positive test, but tertiary alcohols do not.
The Jones reagent will already be prepared for you.

Positive Test
A positive test for aldehydes and primary or secondary alcohols consists in the production of an opaque suspension with a green to blue color. Tertiary alcohols give no visible reaction within 2 seconds, the solution remaining orange in color. Disregard any changes after 15 seconds.

Complications

  • Enols may give a positive test.
  • Phenols give a dark colored solution which is not blue-green like a positive test.

Cleaning up
Place all solutions in the appropriate waste container.

 

Lucas Test for Secondary and Tertiary Alcohols

Alcohols

Standards
1-Butanol, 2-Butanol, t-Butyl alcohol.

Procedures
To 0.2 mL or 0.2 g of the unknown in a test tube add 2 mL of the Lucas reagent at room temperature. Stopper the tube and shake vigorously, then allow the mixture to stand. Note the time required for the formation of the alkyl chloride, which appears as an insoluble layer or emulsion.
The Lucas reagent is already prepared for you.

Positive test
Appearance of a cloudy second layer or emulsion

  • 3o alcohols: immediate to 2-3 minutes
  • 2o alcohols: 5 -10 minutes
  • 1o alcohols: no reaction

Complications
The test applies only to those alcohols soluble in the reagent (monofunctional alcohols lower than hexyl and some polyfunctional alcohols.) This often means that alcohols with more than six carbon atoms cannot be tested.

Cleaning Up
Place all solutions in the appropriate waste container.

+ نوشته شده در  سه شنبه سی ام فروردین 1390ساعت 13:5  توسط ساناز رضائی معصومه سرافراز  | 


1. Product Identification

Synonyms: Oil of vitriol; Babcock acid; sulphuric acid
CAS No.: 7664-93-9
Molecular Weight: 98.08
Chemical Formula: H2SO4 in H2O
Product Codes:
J.T. Baker: 5030, 5137, 5374, 5802, 5815, 5858, 5859, 5868, 5889, 5897, 5961, 5971, 5997, 6163, 6902, 9671, 9673, 9674, 9675, 9676, 9679, 9680, 9681, 9682, 9684, 9687, 9690, 9691, 9693, 9694, 9697
Mallinckrodt: 21201, 2468, 2876, 2878, 2879, 2900, 2904, 3780, 4222, 5524, 5557, H644, H850, H976, H996, V651, XL003

2. Composition/Information on Ingredients


  Ingredient                                CAS No         Percent        Hazardous                                  
  ---------------------------------------   ------------   ------------   ---------   
 
  Sulfuric Acid                             7664-93-9        52 - 100%       Yes                                                                    
  Water                                     7732-18-5         0 - 48%        No                                                                    
 

3. Hazards Identification

Emergency Overview
--------------------------
POISON! DANGER! CORROSIVE. LIQUID AND MIST CAUSE SEVERE BURNS TO ALL BODY TISSUE. MAY BE FATAL IF SWALLOWED OR CONTACTED WITH SKIN. HARMFUL IF INHALED. AFFECTS TEETH. WATER REACTIVE. CANCER HAZARD. STRONG INORGANIC ACID MISTS CONTAINING SULFURIC ACID CAN CAUSE CANCER. Risk of cancer depends on duration and level of exposure.

SAF-T-DATA(tm) Ratings (Provided here for your convenience)
-----------------------------------------------------------------------------------------------------------
Health Rating: 4 - Extreme (Poison)
Flammability Rating: 0 - None
Reactivity Rating: 2 - Moderate
Contact Rating: 4 - Extreme (Corrosive)
Lab Protective Equip: GOGGLES & SHIELD; LAB COAT & APRON; VENT HOOD; PROPER GLOVES
Storage Color Code: White (Corrosive)
-----------------------------------------------------------------------------------------------------------

Potential Health Effects
----------------------------------

Inhalation:
Inhalation produces damaging effects on the mucous membranes and upper respiratory tract. Symptoms may include irritation of the nose and throat, and labored breathing. May cause lung edema, a medical emergency.
Ingestion:
Corrosive. Swallowing can cause severe burns of the mouth, throat, and stomach, leading to death. Can cause sore throat, vomiting, diarrhea. Circulatory collapse with clammy skin, weak and rapid pulse, shallow respirations, and scanty urine may follow ingestion or skin contact. Circulatory shock is often the immediate cause of death.
Skin Contact:
Corrosive. Symptoms of redness, pain, and severe burn can occur. Circulatory collapse with clammy skin, weak and rapid pulse, shallow respirations, and scanty urine may follow skin contact or ingestion. Circulatory shock is often the immediate cause of death.
Eye Contact:
Corrosive. Contact can cause blurred vision, redness, pain and severe tissue burns. Can cause blindness.
Chronic Exposure:
Long-term exposure to mist or vapors may cause damage to teeth. Chronic exposure to mists containing sulfuric acid is a cancer hazard.
Aggravation of Pre-existing Conditions:
Persons with pre-existing skin disorders or eye problems or impaired respiratory function may be more susceptible to the effects of the substance.

4. First Aid Measures

Inhalation:
Remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Call a physician immediately.
Ingestion:
DO NOT INDUCE VOMITING. Give large quantities of water. Never give anything by mouth to an unconscious person. Call a physician immediately.
Skin Contact:
In case of contact, immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before reuse. Excess acid on skin can be neutralized with a 2% solution of bicarbonate of soda. Call a physician immediately.
Eye Contact:
Immediately flush eyes with gentle but large stream of water for at least 15 minutes, lifting lower and upper eyelids occasionally. Call a physician immediately.

5. Fire Fighting Measures

Fire:
Concentrated material is a strong dehydrating agent. Reacts with organic materials and may cause ignition of finely divided materials on contact.
Explosion:
Contact with most metals causes formation of flammable and explosive hydrogen gas.
Fire Extinguishing Media:
Dry chemical, foam or carbon dioxide. Do not use water on material. However, water spray may be used to keep fire exposed containers cool.
Special Information:
In the event of a fire, wear full protective clothing and NIOSH-approved self-contained breathing apparatus with full facepiece operated in the pressure demand or other positive pressure mode. Structural firefighter's protective clothing is ineffective for fires involving this material. Stay away from sealed containers.

6. Accidental Release Measures

Ventilate area of leak or spill. Wear appropriate personal protective equipment as specified in Section 8. Isolate hazard area. Keep unnecessary and unprotected personnel from entering. Contain and recover liquid when possible. Neutralize with alkaline material (soda ash, lime), then absorb with an inert material (e. g., vermiculite, dry sand, earth), and place in a chemical waste container. Do not use combustible materials, such as saw dust. Do not flush to sewer! US Regulations (CERCLA) require reporting spills and releases to soil, water and air in excess of reportable quantities. The toll free number for the US Coast Guard National Response Center is (800) 424-8802.


J. T. Baker NEUTRASORB® acid neutralizers are recommended for spills of this product.

7. Handling and Storage

Store in a cool, dry, ventilated storage area with acid resistant floors and good drainage. Protect from physical damage. Keep out of direct sunlight and away from heat, water, and incompatible materials. Do not wash out container and use it for other purposes. When diluting, always add the acid to water; never add water to the acid. When opening metal containers, use non-sparking tools because of the possibility of hydrogen gas being present. Containers of this material may be hazardous when empty since they retain product residues (vapors, liquid); observe all warnings and precautions listed for the product.

8. Exposure Controls/Personal Protection

Airborne Exposure Limits:
For Sulfuric Acid:
- OSHA Permissible Exposure Limit (PEL) -
1 mg/m3 (TWA)
- ACGIH Threshold Limit Value (TLV) -
0.2 mg/m3(T) (TWA) for sulfuric acid - A2 Suspected Human Carcinogen for sulfuric acid contained in strong inorganic mists.
Ventilation System:
A system of local and/or general exhaust is recommended to keep employee exposures below the Airborne Exposure Limits. Local exhaust ventilation is generally preferred because it can control the emissions of the contaminant at its source, preventing dispersion of it into the general work area. Please refer to the ACGIH document, Industrial Ventilation, A Manual of Recommended Practices, most recent edition, for details.
Personal Respirators (NIOSH Approved):
If the exposure limit is exceeded and engineering controls are not feasible, a full facepiece respirator with an acid gas cartridge and particulate filter (NIOSH type N100 filter) may be worn up to 50 times the exposure limit, or the maximum use concentration specified by the appropriate regulatory agency or respirator supplier, whichever is lowest. If oil particles (e.g. lubricants, cutting fluids, glycerine, etc.) are present, use a NIOSH type R or P particulate filter. For emergencies or instances where the exposure levels are not known, use a full-facepiece positive-pressure, air-supplied respirator. WARNING: Air purifying respirators do not protect workers in oxygen-deficient atmospheres. Where respirators are required, you must have a written program covering the basic requirements in the OSHA respirator standard. These include training, fit testing, medical approval, cleaning, maintenance, cartridge change schedules, etc. See 29CFR1910.134 for details.
Skin Protection:
Wear impervious protective clothing, including boots, gloves, lab coat, apron or coveralls, as appropriate, to prevent skin contact.
Eye Protection:
Use chemical safety goggles and/or a full face shield where splashing is possible. Maintain eye wash fountain and quick-drench facilities in work area.

9. Physical and Chemical Properties

Appearance:
Clear oily liquid.
Odor:
Odorless.
Solubility:
Miscible with water, liberates much heat.
Specific Gravity:
1.84 (98%), 1.40 (50%), 1.07 (10%)
pH:
1 N solution (ca. 5% w/w) = 0.3; 0.1 N solution (ca. 0.5% w/w) = 1.2; 0.01 N solution (ca. 0.05% w/w) = 2.1.
% Volatiles by volume @ 21C (70F):
No information found.
Boiling Point:
ca. 290C (ca. 554F) (decomposes at 340C)
Melting Point:
3C (100%), -32C (93%), -38C (78%), -64C (65%).
Vapor Density (Air=1):
3.4
Vapor Pressure (mm Hg):
1 @ 145.8C (295F)
Evaporation Rate (BuAc=1):
No information found.

10. Stability and Reactivity

Stability:
Stable under ordinary conditions of use and storage. Concentrated solutions react violently with water, spattering and liberating heat.
Hazardous Decomposition Products:
Toxic fumes of oxides of sulfur when heated to decomposition. Will react with water or steam to produce toxic and corrosive fumes. Reacts with carbonates to generate carbon dioxide gas, and with cyanides and sulfides to form poisonous hydrogen cyanide and hydrogen sulfide respectively.
Hazardous Polymerization:
Will not occur.
Incompatibilities:
Water, potassium chlorate, potassium perchlorate, potassium permanganate, sodium, lithium, bases, organic material, halogens, metal acetylides, oxides and hydrides, metals (yields hydrogen gas), strong oxidizing and reducing agents and many other reactive substances.
Conditions to Avoid:
Heat, moisture, incompatibles.

11. Toxicological Information

Toxicological Data:
Oral rat LD50: 2140 mg/kg; inhalation rat LC50: 510 mg/m3/2H; standard Draize, eye rabbit, 250 ug (severe); investigated as a tumorigen, mutagen, reproductive effector.
Carcinogenicity:
Cancer Status: The International Agency for Research on Cancer (IARC) has classified "strong inorganic acid mists containing sulfuric acid" as a known human carcinogen, (IARC category 1). This classification applies only to mists containing sulfuric acid and not to sulfuric acid or sulfuric acid solutions.
  --------\Cancer Lists\------------------------------------------------------
                                         ---NTP Carcinogen---
  Ingredient                             Known    Anticipated    IARC Category
  ------------------------------------   -----    -----------    -------------
  Sulfuric Acid (7664-93-9)               No          No            None
  Water (7732-18-5)                       No          No            None

12. Ecological Information

Environmental Fate:
When released into the soil, this material may leach into groundwater. When released into the air, this material may be removed from the atmosphere to a moderate extent by wet deposition. When released into the air, this material may be removed from the atmosphere to a moderate extent by dry deposition.
Environmental Toxicity:
LC50 Flounder 100 to 330 mg/l/48 hr aerated water/Conditions of bioassay not specified; LC50 Shrimp 80 to 90 mg/l/48 hr aerated water /Conditions of bioassay not specified; LC50 Prawn 42.5 ppm/48 hr salt water /Conditions of bioassay not specified.
This material may be toxic to aquatic life.

13. Disposal Considerations

Whatever cannot be saved for recovery or recycling should be handled as hazardous waste and sent to a RCRA approved incinerator or disposed in a RCRA approved waste facility. Processing, use or contamination of this product may change the waste management options. State and local disposal regulations may differ from federal disposal regulations. Dispose of container and unused contents in accordance with federal, state and local requirements.

14. Transport Information

Domestic (Land, D.O.T.)
-----------------------
Proper Shipping Name: SULFURIC ACID (WITH MORE THAN 51% ACID)
Hazard Class: 8
UN/NA: UN1830
Packing Group: II
Information reported for product/size: 440LB

International (Water, I.M.O.)
-----------------------------
Proper Shipping Name: SULFURIC ACID (WITH MORE THAN 51% ACID)
Hazard Class: 8
UN/NA: UN1830
Packing Group: II
Information reported for product/size: 440LB


15. Regulatory Information

  --------\Chemical Inventory Status - Part 1\---------------------------------
  Ingredient                                       TSCA  EC   Japan  Australia
  -----------------------------------------------  ----  ---  -----  ---------
  Sulfuric Acid (7664-93-9)                         Yes  Yes   Yes      Yes                                      
  Water (7732-18-5)                                 Yes  Yes   Yes      Yes                                      
 
  --------\Chemical Inventory Status - Part 2\---------------------------------
                                                          --Canada--
  Ingredient                                       Korea  DSL   NDSL  Phil.
  -----------------------------------------------  -----  ---   ----  -----
  Sulfuric Acid (7664-93-9)                         Yes   Yes   No     Yes      
  Water (7732-18-5)                                 Yes   Yes   No     Yes
 
  --------\Federal, State & International Regulations - Part 1\----------------
                                             -SARA 302-    ------SARA 313------
  Ingredient                                 RQ    TPQ     List  Chemical Catg.
  -----------------------------------------  ---   -----   ----  --------------
  Sulfuric Acid (7664-93-9)                  1000  1000    Yes        No
  Water (7732-18-5)                          No    No      No         No
 
  --------\Federal, State & International Regulations - Part 2\----------------
                                                        -RCRA-    -TSCA-
  Ingredient                                 CERCLA     261.33     8(d) 
  -----------------------------------------  ------     ------    ------
  Sulfuric Acid (7664-93-9)                  1000       No         No    
  Water (7732-18-5)                          No         No         No                                                                
 
 
Chemical Weapons Convention:  No     TSCA 12(b):  No     CDTA:  Yes
SARA 311/312:  Acute: Yes      Chronic: Yes  Fire: No  Pressure: No
Reactivity: Yes         (Pure / Liquid) 


Australian Hazchem Code: 2P
Poison Schedule: None allocated.
WHMIS:
This MSDS has been prepared according to the hazard criteria of the Controlled Products Regulations (CPR) and the MSDS contains all of the information required by the CPR.

16. Other Information

NFPA Ratings: Health: 3 Flammability: 0 Reactivity: 2 Other: Water reactive
Label Hazard Warning:
POISON! DANGER! CORROSIVE. LIQUID AND MIST CAUSE SEVERE BURNS TO ALL BODY TISSUE. MAY BE FATAL IF SWALLOWED OR CONTACTED WITH SKIN. HARMFUL IF INHALED. AFFECTS TEETH. WATER REACTIVE. CANCER HAZARD. STRONG INORGANIC ACID MISTS CONTAINING SULFURIC ACID CAN CAUSE CANCER. Risk of cancer depends on duration and level of exposure.
Label Precautions:
Do not get in eyes, on skin, or on clothing.
Do not breathe mist.
Keep container closed.
Use only with adequate ventilation.
Wash thoroughly after handling.
Do not contact with water.
Label First Aid:
In all cases call a physician immediately. In case of contact, immediately flush eyes or skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Wash clothing before re-use. Excess acid on skin can be neutralized with a 2% bicarbonate of soda solution. If swallowed, DO NOT INDUCE VOMITING. Give large quantities of water. Never give anything by mouth to an unconscious person. If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen.
Product Use:
Laboratory Reagent.
Revision Information:
No Changes.
Disclaimer:
************************************************************************************************
Mallinckrodt Baker, Inc. provides the information contained herein in good faith but makes no representation as to its comprehensiveness or accuracy. This document is intended only as a guide to the appropriate precautionary handling of the material by a properly trained person using this product. Individuals receiving the information must exercise their independent judgment in determining its appropriateness for a particular purpose. MALLINCKRODT BAKER, INC. MAKES NO REPRESENTATIONS OR WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE WITH RESPECT TO THE INFORMATION SET FORTH HEREIN OR THE PRODUCT TO WHICH THE INFORMATION REFERS. ACCORDINGLY, MALLINCKRODT BAKER, INC. WILL NOT BE RESPONSIBLE FOR DAMAGES RESULTING FROM USE OF OR RELIANCE UPON THIS INFORMATION.
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Prepared by: Environmental Health & Safety
Phone Number: (314) 654-1600
+ نوشته شده در  سه شنبه بیست و سوم فروردین 1390ساعت 14:41  توسط ساناز رضائی معصومه سرافراز  | 

Solubility test
Factors affecting solubility
Usually polar compounds in polar solvents and non-polar compounds in polar solvents than are solved.
Similar increase in force between the molecular composition of reduced solubility is.
Compounds similar in molecular weight will decrease solubility.
No other side in the same compound solubility is increased.
 
Solubility in identification of unknown objects
Using solubility somewhat organic chemical agents in the body determines. For example, acidic compounds, usually in the profit and alkaline compounds, usually in 5% hydrochloric acid are resolved.
Using information about the solubility of some unknown combination of characteristics makes. Dissolution of a body of water to be polar enough to make sure it turns or while benzoic acid is not soluble in water, but if the earnings will be combined production of sodium benzoate, which is easily soluble in water.
Solubility of information about molecular weight gives unknown object, such as the series (homologous) are having a chemical agent, usually those less than 4 Total carbon is dissolved in water and those they count more than five carbon atoms Carbon is usually Namhlvlnd water.
 
Classification based on solubility
Solubility test for each object X must be done. The diagnostic test groups in the main importance is unknown compounds. Common solvents for solubility experiments are:
Acid 5% (HCl 5%)
Sodium hydrogen carbonate 5% (NaHCO3 5%)
Sodium hydroxide 5% (NaOH 5%)
Sulfuric acid (H2SO4)
Water (Water)
Organic solvents (Organic Solvent)
 
Hlalytshan compounds according to the seven groups are:
Group 1) compounds in water and in ether Mhlvlnd
Group 2) water soluble compounds and insoluble in ether
Group 3) insoluble in water but soluble in dilute sodium hydroxide solution, which are divided into two categories:
          
A) dilute solution of sodium hydroxide and sodium bicarbonate 5% solution
          
B) dilute solution of sodium hydroxide and hydrochloric acid in dilute solution
Group 4) insoluble in water but soluble in dilute acid Hydrvklrydryk
Group 5) Hydrvkrbnhayy including carbon, hydrogen and oxygen but not in group 1 to 4, but concentrated sulfuric acid Mhlvlnd
Group 6) All nitrogen or sulfur compounds that are concentrated sulfuric acid and Namhlvlnd
Group 7) compounds that have nitrogen or sulfur and in group 1 to 4 are not. Some compounds in this group Mhlvlnd concentrated sulfuric acid.
Classification based on solubility compounds can be demonstrated as follows. Each of the groups that are marked with the Latin letters as a class-specific groups of compounds solubility are known.
  
 
SA Factor single carboxylic acids of less than six carbon and aromatic acids Svlfvnyk
SB Mynhay single factor less than 7 carbon
S1 single factor alcohols, aldehydes, ketones, ethers, and hopes Nytrylha less than six carbon
S2 salt, organic acids, amine hydrochloride, amino acids, carbohydrates, poly Hydrvksyha, acids multifactorial
A1 strong organic acids, carboxylic acids containing more than six carbon Astkhlafhay phenols with ortho and para electron receptor, beta-D ketones
A2 weak organic acids, phenols, Anvlha, Aymynha, Aymydha, sulfonamides, less than 5 carbon Tyvfnvlha, beta-D ketones
B Mynhay Aliphatic more than 7 carbon aniline (only one phenyl group), some oxy ethers
MN Misc neutral compounds containing nitrogen or sulfur, less than five carbon
N1 less than 9 carbon alcohols, aldehydes, methyl ketones, Ktvnhay ring, esters single factor more than 5 carbon ethers of less than eight carbon Apvksydha
N2 stammerer, Lkynha, ethers, some of aromatic compounds containing active agents, non of high Ktvnhay
I saturated hydrocarbons, Halvalkanha, Holliday Ariel, Ariel D ethers, aromatic with disabled groups
 
Practical Section
Solubility in water
I warm a completely solid powder or 2 drops of liquid samples in test tubes and poured 3 ml of distilled water on it and fold the mixture with your fingers hit. After a while if the effect of liquid or solid sample dissolution has been observed. When the laboratory air is cold moments on the flames gentle heating solution is useful.
 
Solubility in ether
As solubility in water, ether solvent in a test tube completely dry, test to do. View boundary line between two liquid is usually so difficult with shaking, if the solution was cloudy dissolution has been done. Non-ionized compounds, a group factor and the ones that are usually solved in ether.
 
Solubility in 5% profit
Possible to increase the temperature Note. If it seems insoluble compound, the quantity of cortical supernatant removed by dropper and a small tube transfer. 5% hydrochloric acid solution to add to it drop by drop until the solution is acidic. If the deposit was formed, placed third in the group. Never Do not apply to such temperatures may lead to hydrolysis.
 
Solubility in 5% sodium bicarbonate
If desired composition in profit was 5% solution, its solubility in 5% bicarbonate try. Especially carbon dioxide removal note. Carboxylic acids, substituted phenols Svlfvnyk acids and are in this group.
 
Solubility in hydrochloric acid, 5% sodium
Some organic bases such Nftyl amine, chlorine hydrate give water soluble but are much acid deposition. If the solution is in the fourth group. If it seems a little non-soluble liquid with upper dropper and transferred to another tube of 5% soda solution is to add alkaline. Deposits formed in the fourth group X puts. Do not use heat
 
Sodium solubility in concentrated sulfuric acid
The test in dry tubes do. You can see a color change? To create charcoal, gas exit, or cause to be cured deposit note.
 
Solubility in sodium phosphoric acid 85%
Phenomena such as creating color or warming does not exist in this case

+ نوشته شده در  سه شنبه بیست و سوم فروردین 1390ساعت 14:35  توسط ساناز رضائی معصومه سرافراز  | 


Appearance
silvery metallic
General properties
Name, symbol, number chromium, Cr, 24
Pronunciation /ˈkroʊmiəm/ KROH-mee-əm
Element category transition metal
Group, period, block 64, d
Standard atomic weight 51.9961g·mol−1
Electron configuration [Ar] 3d5 4s1
Electrons per shell 2, 8, 13, 1 (Image)
Physical properties
Phase solid
Density (near r.t.) 7.19 g·cm−3
Liquid density at m.p. 6.3 g·cm−3
Melting point 2180 K, 1907 °C, 3465 °F
Boiling point 2944 K, 2671 °C, 4840 °F
Heat of fusion 21.0 kJ·mol−1
Heat of vaporization 339.5 kJ·mol−1
Specific heat capacity (25 °C) 23.35 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 1656 1807 1991 2223 2530 2942
Atomic properties
Oxidation states 6, 5, 4, 3, 2, 1, -1, -2
(strongly acidic oxide)
Electronegativity 1.66 (Pauling scale)
Ionization energies
(more)
1st: 652.9 kJ·mol−1
2nd: 1590.6 kJ·mol−1
3rd: 2987 kJ·mol−1
Atomic radius 128 pm
Covalent radius 139±5 pm
Miscellanea
Crystal structure body-centered cubic
Magnetic ordering AFM (rather: SDW[1])
Electrical resistivity (20 °C) 125 nΩ·m
Thermal conductivity (300 K) 93.9 W·m−1·K−1
Thermal expansion (25 °C) 4.9 µm·m−1·K−1
Speed of sound (thin rod) (20 °C) 5940 m/s
Young's modulus 279 GPa
Shear modulus 115 GPa
Bulk modulus 160 GPa
Poisson ratio 0.21
Mohs hardness 8.5
Vickers hardness 1060 MPa
Brinell hardness 1120 MPa
CAS registry number 7440-47-3
Most stable isotopes
Main article: Isotopes of chromium
iso NA half-life DM DE (MeV) DP
50Cr 4.345% > 1.8×1017y εε - 50Ti
51Cr syn 27.7025 d ε - 51V
γ 0.320 -
52Cr 83.789% 52Cr is stable with 28 neutrons
53Cr 9.501% 53Cr is stable with 29 neutrons
54Cr 2.365% 54Cr is stable with 30 neutrons
v · d · e

Chromium (play /ˈkrmiəm/ KROH-mee-əm) is a chemical element which has the symbol Cr and atomic number 24, first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable. The name of the element is derived from the Greek word "chrōma" (χρώμα), meaning colour,[2] because many of its compounds are intensely coloured. It was discovered by Louis Nicolas Vauquelin in the mineral crocoite (lead chromate) in 1797. Crocoite was used as a pigment, and after the discovery that the mineral chromite also contains chromium this latter mineral was used to produce pigments as well.

Chromium was regarded with great interest because of its high corrosion resistance and hardness. A major development was the discovery that steel could be made highly resistant to corrosion and discoloration by adding chromium to form stainless steel. This application, along with chrome plating (electroplating with chromium) are currently the highest-volume uses of the metal. Chromium and ferrochromium are produced from the single commercially viable ore, chromite, by silicothermic or aluminothermic reaction or by roasting and leaching processes. Although trivalent chromium (Cr(III)) is required in trace amounts for sugar and lipid metabolism, few cases have been reported where its complete removal from the diet has caused chromium deficiency. In larger amounts and different forms chromium can be toxic and carcinogenic. The most prominent example of toxic chromium is hexavalent chromium (Cr(VI)). Abandoned chromium production sites often require environmental cleanup.

 

 Characteristics

Physical

Chromium is remarkable for its magnetic properties: it is the only elemental solid which shows antiferromagnetic ordering at room temperature (and below). Above 38 °C, it transforms into a paramagnetic state.[1]

Passivation

Chromium metal left standing in air is passivated by oxygen, forming a thin protective oxide surface layer. This layer is a spinel structure only a few atoms thick. It is very dense, and prevents the diffusion of oxygen into the underlying material. This barrier is in contrast to iron or plain carbon steels, where the oxygen migrates into the underlying material and causes rusting.[3] The passivation can be enhanced by short contact with oxidizing acids like nitric acid. Passivated chromium is stable against acids. The opposite effect can be achieved by treatment with a strong reducing reactant that destroys the protective oxide layer on the metal. Chromium metal treated in this way readily dissolves in weak acids.[4]

Chromium, unlike metals such as iron and nickel, does not suffer from hydrogen embrittlement. However, it does suffer from nitrogen embrittlement, reacting with nitrogen from air and forming brittle nitrides at the high temperatures necessary to work the metal parts.[5]

Occurrence

Chromium is the 21st most abundant element in Earth's crust with an average concentration of 100 ppm.[6] Chromium compounds are found in the environment, due to erosion of chromium-containing rocks and can be distributed by volcanic eruptions. The concentrations range in soil is between 1 and 3000 mg/kg, in sea water 5 to 800 µg/liter, and in rivers and lakes 26 µg/liter to 5.2 mg/liter.[7]

Crocoite (PbCrO4)

Chromium is mined as chromite (FeCr2O4) ore.[8] About two-fifths of the chromite ores and concentrates in the world are produced in South Africa, while Kazakhstan, India, Russia, and Turkey are also substantial producers. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan and southern Africa.[9]

Although rare, deposits of native chromium exist.[10][11] The Udachnaya Pipe in Russia produces samples of the native metal. This mine is a kimberlite pipe, rich in diamonds, and the reducing environment helped produce both elemental chromium and diamond.[12]

The relation between Cr(III) and Cr(VI) strongly depends on pH and oxidative properties of the location, but in most cases, the Cr(III) is the dominating species,[7] although in some areas the ground water can contain up to 39 µg/liter of total chromium of which 30 µg/liter is present as Cr(VI).[13]

 Isotopes

Naturally occurring chromium is composed of three stable isotopes; 52Cr, 53Cr and 54Cr with 52Cr being the most abundant (83.789% natural abundance). Nineteen radioisotopes have been characterized with the most stable being 50Cr with a half-life of (more than) 1.8×1017 years, and 51Cr with a half-life of 27.7 days. All of the remaining radioactive isotopes have half-lives that are less than 24 hours and the majority of these have half-lives that are less than 1 minute. This element also has 2 meta states.[14]

53Cr is the radiogenic decay product of 53Mn. Chromium isotopic contents are typically combined with manganese isotopic contents and have found application in isotope geology. Mn-Cr isotope ratios reinforce the evidence from 26Al and 107Pd for the early history of the solar system. Variations in 53Cr/52Cr and Mn/Cr ratios from several meteorites indicate an initial 53Mn/55Mn ratio that suggests Mn-Cr isotopic composition must result from in-situ decay of 53Mn in differentiated planetary bodies. Hence 53Cr provides additional evidence for nucleosynthetic processes immediately before coalescence of the solar system.[15]

The isotopes of chromium range in atomic mass from 43 u (43Cr) to 67 u (67Cr). The primary decay mode before the most abundant stable isotope, 52Cr, is electron capture and the primary mode after is beta decay.[14] 53Cr has been posited as a proxy for atmospheric oxygen concentration.[16]

 Compounds


Chromium is a member of the transition metals, in group 6. Chromium(0) has an electronic configuration of 4s13d5, owing to the lower energy of the high spin configuration. Chromium exhibits a wide range of possible oxidation states, where the +3 state is most stable energetically; the +3 and +6 states are most commonly observed in chromium compounds, whereas the +1, +4 and +5 states are rare.[17][18]

The following is the Pourbaix diagram for chromium in pure water, perchloric acid or sodium hydroxide:[7][19] Chromium in water pourbiax diagram.png

(Chromium(III

Chromium(III) chloride hexahydrate ([CrCl2(H2O)4]Cl·2H2O)
Anhydrous chromium(III) chloride (CrCl3)

The oxidation state +3 is the most stable, and a large number of chromium(III) compounds are known. Chromium(III) can be obtained by dissolving elemental chromium in acids like hydrochloric acid or sulfuric acid. The Cr3+ ion has a similar radius (63 pm) to the Al3+ ion (radius 50 pm), so they can replace each other in some compounds, such as in chrome alum and alum. When a trace amount of Cr3+ replaces Al3+ in corundum (aluminium oxide, Al2O3), the red-colored ruby is formed.

Chromium(III) ions in water are invariably octahedrally coordinated with water molecules and anions. The commercially available chromium(III) chloride hydrate is the dark green complex [CrCl2(H2O)4]Cl, but two other forms are known: pale green [CrCl(H2O)5]Cl2, and the violet [Cr(H2O)6]Cl3. If water-free green chromium(III) chloride is dissolved in water then the green solution turns violet after some time, due to the substitution of water for chloride in the inner coordination sphere. This kind of reaction is also observed in chrome alum solutions and other water-soluble chromium(III) salts. The reverse reaction may be induced by heating the solution.

Chromium(III) hydroxide (Cr(OH)3) is amphoteric, dissolving in acidic solutions to form [Cr(H2O)6]3+, and in basic solutions to form [Cr(OH)6]3−. It is dehydrated by heating to form the green chromium(III) oxide (Cr2O3), which is the stable oxide with a crystal structure identical to that of corundum.[4]

Chromium(VI

Chromium(VI) oxide

Chromium(VI) compounds are powerful oxidants at low or neutral pH, and, except the hexafluoride, contain oxygen as a ligand, such as the chromate anion (CrO2−
4
) and chromyl chloride (CrO2Cl2).[4]

Chromium(VI) is most commonly encountered in the chromate (CrO2−
4
) and dichromate (Cr2O2−
7
) anions. Chromate is produced industrially by the oxidative roasting of chromite ore with calcium or sodium carbonate. The chromate and dichromate anions are in equilibrium:

2 CrO2−
4
+ 2 H3O+Cr2O2−
7
+ 3 H2O

The dominant species is therefore, by the law of mass action, determined by the pH of the solution. The change in equilibrium is visible by a change from yellow (chromate) to orange (dichromate), such as when an acid is added to a neutral solution of potassium chromate. At yet lower pH values, further condensation to more complex oxyanions of chromium is possible.

Both the chromate and dichromate anions are strong oxidizing reagents at low pH:[4]

Sodium chromate (Na2CrO4)
Cr2O2−
7
+ 14 H3O+ + 6 e → 2 Cr3+ + 21 H2O0 = 1.33 V)

They are, however, only moderately oxidizing at high pH:[4]

CrO2−
4
+ 4 H2O + 3 eCr(OH)3 + 5 OH0 = −0.13 V)

Chromium(VI) compounds in solution can be detected by adding an acidic hydrogen peroxide solution. The unstable dark blue chromium(VI) peroxide (CrO5) is formed, which can be stabilized as an ether adduct CrO5·OR2.[4]

Chromic acid has the hypothetical formula H2CrO4. It is a vaguely described chemical, despite many well-defined chromates and dichromates are known. The dark red chromium(VI) oxide CrO3, the acid anhydride of chromic acid, is sold industrially as "chromic acid".[4] It can be produced by mixing sulfuric acid with dichromate, and is an strong oxidizing agent.

In 2010, the Environmental Working Group studied the drinking water in 35 American cities. The study was the first nationwide analysis measuring the presence of the chemical in U.S. water systems. The study found measurable hexavalent chromium in the tap water of 31 of the cities sampled, with Norman, Oklahoma, at the top of list; 25 cities had levels that exceeded California's proposed limit.[20] Note: Concentrations of Cr VI in US municipal drinking water supplies reported by EWG are within likely, natural background levels for the areas tested and not necessarily indicative of industrial pollution (CalEPA Fact Sheet), as asserted by EWG. This factor was not taken into consideration in their report.

[ Chromium(IV) and chromium(V)

the oxidation state +5 is only realized in few compounds but are important intermediates in many reactions involving chromate. The only binary compound is the volatile chromium(V) fluoride (CrF5). This red solid has a melting point of 30 °C and a boiling point of 117 °C. It can be synthesized by treating chromium metal with fluorine Aat 400 °C and 200 bar pressure. The peroxochromate(V) is another example of the +5 oxidation state. Potassium peroxochromate (K3[Cr(O2)4]) is made by reacting potassium chromate with hydrogen peroxide at low temperatures. This red brown compound is stable at room temperature but decomposes spontaneously at 150–170 °C.[21]

Chromium(IV) compounds (in the +4 oxidation state) are slightly more stable than the chromium(V) compounds. The tetrahalides, CrF4, CrCl4, and CrBr4, can be produced by reacting the trihalides (CrX3) with excess amounts of the corresponding halogen at elevated temperatures. Most of the compounds are susceptible to disproportionation reactions and are not stable in water.

(Chromium(I) and chromium(II)

Many chromium(II) compounds are known, including the water-stable chromium(II) chloride, CrCl2, which can be made by reduction of chromium(III) chloride with zinc. The resulting bright blue solution is only stable at neutral pH.[4] Many chromous carboxylates are also known, most famously, the red chromous acetate (Cr2(O2CCH3)4), which features a quadruple bond. Via X-ray diffraction, an example of a Cr-Cr quintuple bond (length 183.51(4) pm) has been described.[22] Extremely bulky monodentate ligands stabilize this compound by shielding the quintuple bond from further reactions.

Chromium compound determined experimentally to contain a Cr-Cr quintuple bond

 History

Weapons found in burial pits dating from the late 3rd century BC Qin Dynasty of the Terracotta Army near Xi'an, China have been analyzed by archaeologists. Although buried more than 2,000 years ago, the ancient bronze tips of crossbow bolts and swords found at the site showed no sign of corrosion, because the bronze was coated with chromium.[23]

Chromium came to the attention of westerners in the 18th century. On 26 July 1761, Johann Gottlob Lehmann found an orange-red mineral in the Beryozovskoye mines in the Ural Mountains which he named Siberian red lead. Though misidentified as a lead compound with selenium and iron components, the mineral was Crocoite (lead chromate) with a formula of PbCrO4.[24]

In 1770, Peter Simon Pallas visited the same site as Lehmann and found a red lead mineral that had useful properties as a pigment in paints. The use of Siberian red lead as a paint pigment developed rapidly. A bright yellow pigment made from crocoite also became fashionable.[24]

The red colour of rubies is from a small amount of chromium(III).

In 1797, Louis Nicolas Vauquelin received samples of crocoite ore. He produced chromium oxide (CrO3) by mixing crocoite with hydrochloric acid. In 1798, Vauquelin discovered that he could isolate metallic chromium by heating the oxide in a charcoal oven.[25] He was also able to detect traces of chromium in precious gemstones, such as ruby or emerald.[24][26]

During the 1800s, chromium was primarily used as a component of paints and in tanning salts. At first, crocoite from Russia was the main source, but in 1827, a larger chromite deposit was discovered near Baltimore, United States. This made the United states the largest producer of chromium products till 1848 when large deposits of chromite where found near Bursa, Turkey.[8]

Chromium is also known for its luster when polished. It is used as a protective and decorative coating on car parts, plumbing fixtures, furniture parts and many other items, usually applied by electroplating. Chromium was used for electroplating as early as 1848, but this use only became widespread with the development of an improved process in 1924.[27]

Metal alloys now account for 85% of the use of chromium. The remainder is used in the chemical industry and refractory and foundry industries.

 Production

Piece of chromium produced with aluminothermic reaction
World production trend of chromium

Approximately 4.4 million metric tons of marketable chromite ore were produced in 2000, and converted into ~3.3 million tons of ferro-chrome with an approximate market value of 2.5 billion United States dollars.[28] The largest producers of chromium ore have been South Africa (44%) India (18%), Kazakhstan (16%) Zimbabwe (5%), Finland (4%) Iran (4%) and Brazil (2%) with several other countries producing the rest of less than 10% of the world production.[28]

The two main products of chromium ore refining are ferrochromium and metallic chromium. For those products the ore smelter process differs considerably. For the production of ferrochromium, the chromite ore (FeCr2O4) is reduced in large scale in electric arc furnace or in smaller smelters with either aluminium or silicon in an aluminothermic reaction.[29]

Chromium ore output in 2002[28]

For the production of pure chromium, the iron has to be separated from the chromium in a two step roasting and leaching process. The chromite ore is heated with a mixture of calcium carbonate and sodium carbonate in the presence of air. The chromium is oxidized to the hexavalent form, while the iron forms the stable Fe2O3. The subsequent leaching at higher elevated temperatures dissolves the chromates and leaves the insoluble iron oxide. The chromate is converted by sulfuric acid into the dichromate.[29]

4 FeCr2O4 + 8 Na2CO3 + 7 O2 → 8 Na2CrO4 + 2 Fe2O3 + 8 CO2
2 Na2CrO4 + H2SO4 → Na2Cr2O7 + Na2SO4 + H2O

The dichromate is converted to the chromium(III) oxide by reduction with carbon and then reduced in an aluminothermic reaction to chromium.[29]

Na2Cr2O7 + 2 C → Cr2O3 + Na2CO3 + CO
Cr2O3 + 2 Al → Al2O3 + 2 Cr

[ Applications

[ Metallurgy

Decorative chrome plating on a motorcycle.

The strengthening effect of forming stable metal carbides at the grain boundaries and the strong increase in corrosion resistance made chromium an important alloying material for steel. The high speed tool steels contain between 3 and 5% chromium. Stainless steel, the main corrosion-proof metal alloy, is formed when chromium is added to iron in sufficient concentrations, usually above 11%. For its formation, ferrochromium is added to the molten iron. Also nickel-based alloys increase in strength due to the formation of discrete, stable metal carbide particles at the grain boundaries. For example, Inconel 718 contains 18.6% chromium. Because of the excellent high temperature properties of these nickel superalloys, they are used in jet engines and gas turbines in lieu of common structural materials.[30]

The relative high hardness and corrosion resistance of unalloyed chromium makes it a good surface coating, being still the most "popular" metal coating with unbeatable combined durability. A thin layer of chromium is deposited on pretreated metallic surfaces by electroplating techniques. There are two deposition methods: Thin, below 1 µm thickness, layers are deposited by chrome plating, and are used for decorative surfaces. If wear-resistant surfaces are needed then thicker chromium layers are deposited. Both methods normally use acidic chromate or dichromate solutions. To prevent the energy consuming change in oxidation state, the use of Chromium(III) sulfate is under development, but for most applications, the established process is used.[27]

In the chromate conversion coating process, the strong oxidative properties of chromates are used to deposit a protective oxide layer on metals like aluminium, zinc and cadmium. This passivation and the self healing properties by the chromate stored in the chromate conversion coating, which is able to migrate to local defects, are the benefits of this coating method.[31] Because of environmental and health regulations on chromates, alternative coating method are under development.[32]

Anodizing of aluminium is another electrochemical process, which does not lead to the deposition of chromium, but uses chromic acid as electrolyte in the solution. During anodization, an oxide layer is formed on the aluminium. The use of chromic acid, instead of the normally used sulfuric acid, leads to a slight difference of these oxide layers.[33] The high toxicity of Cr(VI) compounds, used in the established chromium electroplating process, and the strengthening of safety and environmental regulations demand a search for substitutes for chromium or at least a change to less toxic chromium(III) compounds.[27]

 

The mineral crocoite (lead chromate PbCrO4) was used as a yellow pigment shortly after its discovery. After a synthesis method became available starting from the more abundant chromite, chrome yellow was, together with cadmium yellow, one of the most used yellow pigments. The pigment does not degrade in the light and has a strong color. The signaling effect of yellow was used for school buses in the United States and for Postal Service (for example Deutsche Post) in Europe. The use of chrome yellow declined due to environmental and safety concerns and was substituted by organic pigments or other lead-free alternatives. Other pigments based on chromium are, for example, the bright red pigment chrome red, which is a basic lead chromate (PbCrO4·Pb(OH)2). Chrome green is a mixture of Prussian blue and chrome yellow, while the chrome oxide green is Chromium(III) oxide.[35]

Glass is colored green by the addition of chromium(III) oxide. This is similar to emerald, which is also colored by chromium.[36] A red color is achieved by doping chromium(III) into the crystals of corundum, which are then called ruby. Therefore, chromium is used in producing synthetic rubies.[37]

The toxicity of chromium(VI) salts is used in the preservation of wood. For example, chromated copper arsenate (CCA) is used in timber treatment to prevent wood from decay fungi, wood attacking insects, including termites, and marine borers.[38] The formulations contain chromium based on the oxide CrO3 between 35.3% and 65.5%. In the United States, 65,300 metric tons of CCA solution have been used in 1996.[38]

 Tanning

Chromium(III) salts, especially chrome alum and chromium(III) sulfate, are used in the tanning of leather. The chromium(III) stabilizes the leather by cross linking the collagen fibers within the leather.[39] Chromium tanned leather can contain between 4 and 5% of chromium, which is tightly bound to the proteins.[8] Better management of chromium in tanning industry such as recovery and reuse, direct/indirect recycling,[40] use of less chrome or chrome less tanning are practised to better manage chromium in tanning.

 Refractory material

The high heat resistivity and high melting point makes chromite and chromium(III) oxide a material for high temperature refractory applications, like blast furnaces, cement kilns, molds for the firing of bricks and as foundry sands for the casting of metals. In these applications, the refractory materials are made from mixtures of chromite and magnesite. The use is declining because of the environmental regulations due to the possibility of the formation of chromium(VI).[29]

 Other use

Several chromium compounds are used as catalysts. For example the Phillips catalysts for the production of polyethylene are mixtures of chromium and silicon dioxide or mixtures of chromium and titanium and aluminium oxide.[41] Chromium(IV) oxide (CrO2) is a magnetic compound. Its ideal shape anisotropy, which imparts high coercivity and remanent magnetization, made it a compound superior to the γ-Fe2O3. Chromium(IV) oxide is used to manufacture magnetic tape used in high-performance audio tape and standard audio cassettes.[42] Chromates can prevent corrosion of steel under wet conditions, and therefore chromates are added to drilling muds.[43] Chromium has been suggested to be connected to sugar metabolism, although no biological role for chromium has ever been demonstrated biochemically. The dietary supplements for chromium include chromium(III) picolinate, chromium(III) polynicotinate, and related materials. The benefit of those supplements is still under investigation and is questioned by some studies.[44][45]

  • Chromium(III) oxide is a metal polish known as green rouge.
  • Chromic acid is a powerful oxidizing agent and is a useful compound for cleaning laboratory glassware of any trace of organic compounds. It is prepared in situ by dissolving potassium dichromate in concentrated sulfuric acid, which is then used to wash the apparatus. Sodium dichromate is sometimes used because of its higher solubility (50 g/L vs. 200 g/L respectively). Potassium dichromate is a chemical reagent, used in cleaning laboratory glassware and as a titrating agent. It is also used as a mordant (i.e., a fixing agent) for dyes in fabric.

 Biological role

Trivalent chromium is a nutritional component for a large class of organisms.[46] Trivalent chromium (Cr(III) or Cr3+) in trace amounts influences sugar and lipid metabolism in humans, and its deficiency is suspected to cause a disease called chromium deficiency.[47] However, chromium deficiency is thought to be extremely rare in the general population and has only ever been confirmed in three people on parenteral nutrition, which is when a patient is fed a liquid diet through intravenous drips.[48] In contrast, hexavalent chromium (Cr(VI) or Cr6+) is very toxic and mutagenic when inhaled. Cr(VI) has not been established as a carcinogen when in solution, though it may cause allergic contact dermatitis (ACD).[49]

The use of chromium-containing dietary supplements is controversial due to the complex effects of the used supplements.[50] The popular dietary supplement chromium picolinate complex generates chromosome damage in hamster cells.[51] In the United States the dietary guidelines for daily chromium uptake were lowered from 50–200 µg for an adult to 35 µg (adult male) and to 25 µg (adult female).[52]

 Precautions

Water insoluble chromium(III) compounds and chromium metal are not considered a health hazard, while the toxicity and carcinogenic properties of chromium(VI) have been known for a long time.[53]

Because of the specific transport mechanisms, only limited amounts of chromium(III) enter the cells. Several in vitro studies indicated that high concentrations of chromium(III) in the cell can lead to DNA damage.[54] Acute oral toxicity ranges between 1.5 and 3.3 mg/kg.[55] The proposed beneficial effects of chromium(III) and the use as dietary supplements yielded some controversial results, but recent reviews suggest that moderate uptake of chromium(III) through dietary supplements poses no risk.[54]

The acute oral toxicity for chromium(VI) ranges between 50 and 150 µg/kg.[55] In the body, chromium(VI) is reduced by several mechanisms to chromium(III) already in the blood before it enters the cells. The chromium(III) is excreted from the body, whereas the chromate ion is transferred into the cell by a transport mechanism, by which also sulfate and phosphate ions enter the cell. The acute toxicity of chromium(VI) is due to its strong oxidational properties. After it reaches the blood stream, it damages the kidneys, the liver and blood cells through oxidation reactions. Hemolysis, renal and liver failure are the results of these damages. Aggressive dialysis can improve the situation.[56]

The carcinogenity of chromate dust is known for a long time, and in 1890 the first publication described the elevated cancer risk of workers in a chromate dye company.[57][58] Three mechanisms have been proposed to describe the genotoxicity of chromium(VI). The first mechanism includes highly reactive hydroxyl radicals and other reactive radicals which are by products of the reduction of chromium(VI) to chromium(III). The second process includes the direct binding of chromium(V), produced by reduction in the cell, and chromium(IV) compounds to the DNA. The last mechanism attributed the genotoxicity to the binding to the DNA of the end product of the chromium(III) reduction.[59]

Chromium salts (chromates) are also the cause of allergic reactions in some people. Chromates are often used to manufacture, amongst other things, leather products, paints, cement, mortar and anti-corrosives. Contact with products containing chromates can lead to allergic contact dermatitis and irritant dermatitis, resulting in ulceration of the skin, sometimes referred to as "chrome ulcers". This condition is often found in workers that have been exposed to strong chro

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