Improper storage of reagents can lead to their failure and deterioration, affecting experimental results, causing waste of materials, and sometimes even accidents. Therefore, scientifically storing reagents is crucial for ensuring smooth experiments and obtaining reliable experimental data. The deterioration of chemical reagents is mostly due to the influence of external conditions, such as oxygen, carbon dioxide, water vapor, acidic and alkaline substances in the air, as well as ambient temperature and light. These factors can cause chemical reagents to undergo oxidation, reduction, deliquescence, efflorescence, crystallization, dilution, corrosion, decomposition, volatilization, sublimation, polymerization, mildew, discoloration, and combustion/explosion.

1. Influence of Storage Conditions on Chemical Reagents.

(1). Influence of various components in the air.

Oxidizing and reducing substances; In addition to oxygen, the air sometimes contains nitrogen dioxide, sulfur dioxide, hydrogen sulfide, and bromine vapor. Most low-valence ions in inorganic reagents, such as ferrous ions and stannous ions, active metals, and reducing compounds in organic reagents, are easily oxidized by oxidizing substances in the air; strong oxidizing agents in inorganic reagents are easily reduced by reducing substances in the air. The influence of this factor can cause reagents to decrease or lose their original oxidizing and reducing capacity.

Carbon Dioxide: Carbon dioxide is an acidic oxide that forms carbonic acid with water vapor in the air. It is easily absorbed by bases (e.g., sodium hydroxide, calcium hydroxide, butylenediamine, etc.), strong base weak acid salts (sodium arsenate, sodium silicate), compounds that can form insoluble carbonates with carbonic acid (e.g., calcium, strontium, barium, lead, magnesium, cadmium salts, etc.), and by some organic reagents. Therefore, if reagents with the above properties are not properly sealed, they will be corroded and deteriorate by carbon dioxide.

Acidic and Alkaline Gases: Acidic or alkaline gases, such as hydrogen sulfide, hydrogen chloride, sulfur dioxide, nitrogen dioxide, and ammonia, which are produced during experiments or due to improper sealing of reagent bottles, can combine with water vapor in the air to form acidic or alkaline mist droplets. These droplets adhere to the reagent bottles, contaminating the reagents.

Water Vapor: When the water vapor content in the air is too high, desiccants and standard substances for volumetric analysis are easily affected by moisture and become unusable. Some substances, such as halides, nitrates, carbonates, and citrates, easily absorb water and deliquesce, and some may even undergo hydrolysis and be difficult to recover. Ammonium persulfate loses its oxidizing properties by releasing oxygen after hygroscopic hydrolysis; sodium sulfide becomes a liquid and releases hydrogen sulfide after absorbing moisture; anhydrous aluminum chloride hydrolyzes into aluminum hydroxide and produces hydrochloric acid, etc.

However, when the air is too dry, some reagents containing crystal water are prone to efflorescence, causing the reagents to turn into powder.

Therefore, indoor humidity is also an important condition for reagent storage.

(2). Influence of temperature.

Temperature has a significant impact on reagents. Generally, the higher the temperature, the more easily reagents deteriorate, especially organic reagents, which are more susceptible to temperature. For instance, low molecular weight alcohols, ethers, aldehydes, ketones, esters, benzene and its derivatives, nitro compounds, and other organic reagents, as well as hydrochloric acid, nitric acid, and ammonia water, are highly volatile when heated. Furthermore, substances like methyl methacrylate, styrene, and acrylic acid will polymerize or deteriorate when the temperature exceeds -10℃ and must be cold-stored at low temperatures. When the ambient temperature of flammable substances exceeds their flash point, it can cause combustion. Peroxides, when at higher temperatures, can decompose and explode, and are best stored in a refrigerator.

(3). Influence of light.

When reagents are exposed to light (especially ultraviolet light), they can undergo decomposition, oxidation-reduction reactions, or self-oxidation-reduction reactions. Examples include silver oxides and salts, mercuric and mercurous oxides, halides (except fluorine) and their salts, and some salts of bromine and iodine. Therefore, many reagents should be stored in brown bottles, as brown bottles absorb ultraviolet light, preventing the influence of light on the reagents.

2. General requirements for storing reagents.

(1). Chemical reagents should be stored as little as possible in the laboratory to prevent contamination of the laboratory by volatile reagents and to avoid the influence of substances produced by chemical experiments on chemical reagents. It is best to have a dedicated room for storing chemical reagents.

(2). Chemical reagents should be placed in dedicated glass reagent cabinets that are dust-proof and prevent contamination and corrosion by various vapors or gases. They should be stored classified according to their properties.

(3). The indoor environment should maintain a certain temperature and humidity. Strong light exposure should be avoided, and good ventilation equipment should be available.

(4). Reagents in storage should be regularly checked to ensure the labels on the bottles are intact and the writing is clear. If they fall off or become blurred, they should be replaced promptly.

(5). The room should be equipped with fire-fighting equipment and sandboxes.

3. Storage requirements and precautions for various dangerous goods.

(1) Flammable liquids are mainly organic solvents, such as ethanol, ether, acetone, carbon disulfide, benzene, toluene, gasoline, etc. They are highly volatile and turn into gas, igniting immediately upon contact with an open flame. These liquids should be stored separately, kept in a cool, ventilated place, and especially away from ignition sources.

Flammable solid inorganic substances such as sulfur, red phosphorus, magnesium powder, and aluminum powder have very low ignition points; their storage areas should be ventilated and dry. White phosphorus can spontaneously combust in the air and should be stored in water, in a dark, cool place. The water level in the bottle should be checked frequently to prevent water evaporation from exposing the white phosphorus to the air.

(2) Substances that burn or explode upon contact with water, such as metallic potassium, sodium, calcium, calcium carbide, and zinc powder, can react violently with water, releasing flammable gases and easily causing explosions. Potassium and sodium should be stored in kerosene. Calcium carbide and zinc powder should be kept in a dry place. These substances should be stored separately from flammable materials, strong oxidizing agents, etc. When not in use for a long time, they should be hermetically sealed, and containers holding these substances should be placed in a cement or brick-built trough.

(3)Strong oxidizers: These reagents include peroxides (hydrogen peroxide, sodium peroxide, barium peroxide), strong oxidizing oxyacids (perchloric acid), and strong oxidizing oxyacid salts (nitrates, chlorates, dichromates, permanganates). Explosions may occur when heated, impacted, or mixed with reducing agents. When storing, they must not be placed together with combustibles, flammables, and reducing agents. The storage area should be cool and well-ventilated.

(4)Strong corrosives: Strong acids, strong bases, liquid bromine, phosphorus trichloride, phosphorus pentoxide, anhydrous aluminum chloride, and ammonia water, etc., are highly corrosive to human skin, mucous membranes, eyes, respiratory organs, and metals. When storing, they should be separated from other reagents and placed on shelves made of corrosion-resistant materials (acid-resistant cement or acid-resistant ceramics). The shelves should not be too high to ensure safe and convenient access.

(5)Poisons: Cyanides, arsenic trioxide or other arsenicals, mercuric chloride (sublimate), etc., are highly toxic reagents, and even a very small amount ingested can cause fatal poisoning. They should be locked in a fixed iron cabinet and managed by a dedicated person. Soluble copper salts, barium salts, lead salts, and antimony salts are also poisons and should be properly stored.