How important is it to classify and store laboratory chemical reagents?

Reagents are indispensable for any experiment. Reagents not only have various states, but also different reagents have very different performances. Some are very stable at room temperature, some are usually very active, some do not deteriorate at high temperatures, some are flammable and explosive, some have strong aromas, and some are highly toxic. Only by having a deep understanding of the relevant knowledge of chemical reagents can various experiments be carried out safely and smoothly. It can not only ensure that the expected experimental purpose is achieved, but also eliminate pollution to the environment. Therefore, we must first know the classification of reagents. Then master the storage and use of various reagents.

Reagents are also called chemical reagents or test drugs. They are mainly pure chemicals used to achieve chemical reactions, analytical tests, research experiments, teaching experiments, and chemical formulas. They are generally divided into general reagents, high-purity reagents, analytical reagents, instrumental analytical reagents, clinical diagnostic reagents, biochemical reagents, inorganic ion colorimetric reagents, etc.

Super pure or first grade (GR, precision analysis and scientific research); analytically pure or second grade (AR, important analysis and general research); chemically pure or third grade (CP, general chemical experiments in industry, mining and schools); experimental reagents (LP).

The grade and specifications of reagents should be selected according to specific requirements and usage. The basis for classification is the purity (i.e. content) of the reagent, the impurity content, the difficulty of purification, and various physical properties. Sometimes it is also graded according to the purpose, such as spectrally pure reagents, chromatographically pure reagents, and pH standard reagents, etc.

Most chemical reagents are toxic and dangerous. Strengthening the management of chemical reagents is not only necessary to ensure the quality of analytical results, but also to ensure the safety of people's lives and property. The management of chemical reagents should be properly managed in different ways according to the different characteristics of the reagents, such as toxicity, flammability, corrosiveness and deliquescent properties.

Only a small amount of medicines needed in the short term should be stored in the laboratory. Flammable and explosive reagents should be placed in an iron cabinet with ventilation holes on the top of the cabinet. It is strictly forbidden to store flammable liquids in bottles with a total volume of 20L in the laboratory. Large amounts of reagents should be placed in the reagent warehouse. For general reagents, such as inorganic salts, they should be stored in an orderly manner in the reagent cabinet. They can be stored according to the element periodic system, or according to acids, alkalis, salts, oxides, etc. When storing reagents, pay attention to the storage period of chemical reagents. Some reagents will gradually deteriorate during storage and even form harmful substances. For example, ethers, tetrahydrofuran, dioxane, olefins, liquid paraffin, etc., can form peroxides if exposed to air under light conditions. The longer they are stored, the more dangerous they are. Some reducing reagents, such as benzyltriol, TiCl3, sodium tetrahydroborate, FeS04, vitamin C, vitamin E, and metal iron wire, aluminum, magnesium, zinc powder, etc., are easily oxidized and deteriorated by oxygen in the air. Chemical reagents must be stored separately and cannot be mixed together. Reagents are usually divided into the following categories and stored separately.

1) Flammable liquids are very easy to volatilize into gas and burn when exposed to open flames. Liquids with flash points below 25°C are usually classified as flammable. Those with flash points below -4°C include petroleum ether, ethyl chloride, ethyl bromide, ether, gasoline, carbon disulfide, acetal, acetone, benzene, ethyl acetate, methyl acetate, etc. Those with flash points below 25°C include butanone, toluene, methanol, ethanol, isopropanol, xylene, butyl acetate, amyl acetate, trioxymethylene, pyridine, etc. These reagents are required to be stored separately in a cool and ventilated place, and the ideal storage temperature is -4 to 4°C. For reagents with a flash point below 25°C, the maximum room temperature should not exceed 30°C, and special attention should be paid to keep them away from fire sources.

2) Highly toxic reagents refer specifically to reagents that can cause poisoning and death even if a very small amount of them invade the digestive tract. Those with a median lethal dose of less than 50mg/kg in biological tests are called highly toxic substances, such as potassium cyanide, sodium cyanide and other highly toxic cyanides, arsenic trioxide and other highly toxic arsenides, mercuric chloride and other extremely toxic mercuric salts, dimethyl sulfate, certain alkaloids and toxins, etc. Such reagents should be placed in a cool and dry place, isolated from acid reagents. They should be locked in a special drug cabinet, and a two-person registration and signature system should be established for use. Establish systems for use, consumption, and waste disposal. It is forbidden to operate such substances when there are wounds on the skin.

3) Strongly corrosive category Refers to liquids and solids (including vapor) that are extremely corrosive to human skin, mucous membranes, eyes, respiratory tract and objects, such as fuming sulfuric acid, sulfuric acid, fuming nitric acid, hydrochloric acid, hydrofluoric acid, hydrobromic acid, chlorosulfonic acid, chlorinated sulfone, monochloroacetic acid, formic acid, acetic anhydride, chlorinated phosphorus, phosphorus pentoxide, anhydrous aluminum chloride, bromine, sodium hydroxide, potassium hydroxide, sodium sulfide, phenol, anhydrous hydrazine, hydrazine hydrate, etc. The storage place should be cool and ventilated, and separated from other drugs. Corrosion-resistant materials such as acid-resistant cement or acid-resistant ceramics should be used to make shelves to place such drugs. The rack should not be too high or placed on a high shelf. It is best to place it on the ground against the wall to ensure safe storage.

4) Explosive category Among these reagents, potassium, sodium, lithium, calcium, lithium aluminum hydride, calcium carbide, etc. react violently with water and cause combustion and explosion. Potassium and sodium should be stored in kerosene. Reagents that are explosives or highly explosive include nitrocellulose, picric acid, trinitrotoluene, trinitrobenzene, azide or diazo compounds, fulminates, etc., so they should be handled with care. Substances that can undergo strong oxidation and cause combustion when in contact with air, such as yellow phosphorus, should be stored in water, and cutting should also be done in water. Substances with low flash points that can burn rapidly or even explode when heated, impacted, rubbed, or in contact with oxidants include phosphorus sulfide, red phosphorus, magnesium powder, zinc powder, aluminum powder, naphthalene, and camphor. Such reagents require that the indoor temperature for storage does not exceed 30°C, and they must be stored separately from flammable materials and oxidants. The material rack is made of bricks and cement, with a groove, and fire sand is laid in the groove. The reagents are placed in the sand and covered to prevent the situation from escalating in case of an accident.

5) Strong oxidants This type of reagent is a peroxide or oxygen-containing acid and its salt, which will explode under appropriate conditions and can form an explosive mixture with flammable solids such as organic matter, magnesium, aluminum, zinc powder, and sulfur. Some of these substances can react violently with water, such as peroxides, which are at risk of explosion when in contact with water. These substances include ammonium nitrate, potassium nitrate, sodium nitrate, perchloric acid, potassium perchlorate, sodium perchlorate, magnesium perchlorate or barium, chromic anhydride, ammonium dichromate, potassium dichromate and other chromates, potassium permanganate and other permanganates, potassium chlorate, barium chlorate, ammonium persulfate and other persulfates, sodium peroxide, potassium peroxide, barium peroxide, dibenzoyl peroxide, peracetic acid, etc. The storage area should be cool and ventilated, and the maximum temperature should not exceed 30°C. It should be isolated from acids and flammable, combustible or easily oxidized (i.e. reducing substances) such as sawdust, charcoal powder, sulfide, sugar, etc. The stacking should not be too high or too large, and attention should be paid to heat dissipation.

6) Radioactive substances It is impossible for general laboratories to have radioactive substances. The laboratory operation of these substances requires special protective equipment and knowledge to protect personal safety and prevent contamination and spread of radioactive substances. The above 6 categories are all dangerous goods.

7) Low-temperature storage category This type of reagent needs to be stored at low temperature to avoid polymerization, deterioration or other accidents. Methyl methacrylate, styrene, acrylonitrile, vinyl acetylene and other polymerizable monomers, hydrogen peroxide, ammonium hydroxide, etc. belong to this category. Store at a temperature below 10°C.

8) Precious category Special reagents with high unit prices, ultra-pure reagents, rare elements and their compounds all belong to this category. Most of these reagents are in small packages. This type of reagent should be stored separately from general reagents, and management should be strengthened and a collection system should be established. Common ones include palladium black, palladium chloride, platinum chloride, platinum, iridium, platinum asbestos, gold chloride, gold powder, rare earth elements, etc. 9) Indicators and organic reagents Indicators can be classified and arranged according to acid-base indicators, redox indicators, complexometric titration indicators and fluorescent adsorption indicators. Organic reagents can be arranged according to the number of carbon atoms in the molecule. 10) General reagents General reagents can be classified and stored in a cool and ventilated cabinet with a temperature below 30°C.