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What are the storage requirements for laboratory chemical reagents?
1. Specification of chemical reagents
According to national standards (GB) and ministerial standards, chemical reagents are classified into four grades according to their purity and magazine content (see Table 1).
(1) Premium pure reagents, also known as guaranteed reagents, are first-class products with high purity and few impurities. They are mainly used for precision analysis and scientific research, and are often expressed in GR.
(2) Analytical pure reagent, also known as analytical reagent, is a secondary product with a slightly lower purity and a slightly higher impurity content. It is suitable for important analysis and general research work and is often expressed in AR.
(3) Chemical pure reagent is a third-class product. Its purity is worse than that of analytical reagent, but higher than that of experimental reagent. It is suitable for general analysis work in factories and schools. It is often expressed as CP.
(4) The experimental reagent is a fourth-grade product. Its purity is worse than that of chemical products, but higher than that of industrial products. It is mainly used in general chemical experiments and cannot be used in analytical work. It is often expressed in LR.
In addition to the above grades, chemical reagents include benchmark reagents, spectral pure reagents and ultrapure reagents.
The reference reagent is equivalent to or higher than the high-grade pure reagent. It is used as the reference substance for titration analysis to determine the exact concentration of unknown solution or to prepare standard solution directly. Its principal component content is generally between 99.95% and 100.0%, and the total impurity content is not more than 0.05%.
Spectral pure reagents are mainly used as reference materials in spectral analysis. Their impurities can not be detected by spectral analysis or are below a certain limit. The purity of the reagents is over 99.99%. Ultra-pure reagents, also known as high-purity reagents, are produced by special equipment such as quartz and platinum utensils.
2. Storage of reagents
Chemical reagents often deteriorate due to improper storage. Some reagents are easily hygroscopically degraded or hydrolyzed; some react with oxygen, carbon dioxide or other gases diffused in the air; and some deteriorate under the influence of light and environmental temperature. Therefore, appropriate measures must be taken to preserve the reagents properly according to their different properties. Generally, there are several methods of preservation as follows:
(1) Sealed preservation
After reagents are taken, they are usually sealed with plugs. Especially volatile substances (such as nitric acid, hydrochloric acid, ammonia) and many low boiling point organic substances (such as ether, acetone, formaldehyde, acetaldehyde, chloroform, benzene, etc.) must be tightly sealed.
(2) Wax seal
Some reagents, such as phosphorus pentoxide and anhydrous AlCl3, which have strong hygroscopicity or strong hydrolysis in the presence of water vapor, should not only be tightly sealed, but also wax sealed.
(3) Water preservation
White phosphorus, which can spontaneously ignite in air, is stored in water. The active metal potassium and sodium should be kept in kerosene.
(4) Place brown bottles in shade
Reagents easily deteriorated by light or heat (e.g., concentrated nitric acid, silver nitrate, mercury chloride, potassium iodide, hydrogen peroxide, bromine water and chlorine water) should be stored in brown bottles and kept in a cool place to prevent their decomposition and deterioration.
3. Hazardous drugs should be stored separately from other drugs.
Chemical dangerous substances which are prone to explosion, combustion, poisoning, corrosion and radioactivity, as well as chemicals which can cause disastrous accidents under the influence of external factors, are all chemical dangerous goods.
They must be stored separately, for example, perchloric acid can not also be in contact with organic matter, otherwise explosion is prone.
Strong oxidizing substances and organic solvents can corrode rubber and cannot be stored in glass bottles with rubber stoppers.
Reagents, such as hydrofluoric acid, fluoride salts (potassium fluoride, sodium fluoride, ammonium fluoride) and caustic alkali (potassium hydroxide, sodium hydroxide), which are easy to erode glass and affect the purity of reagents, should be stored in polyethylene plastic bottles or glass bottles coated with paraffin.
Serious drugs must be stored in safe and locked.
When using it, two or more people should work together, and record the use and quantity, take it as it is used, and strictly manage it. The corrosive reagent should have a special storage cabinet.