Purchase and storage of laboratory chemicals
chemical reagentIt is the most diverse, most frequently consumed, and most dangerous substance in the laboratory. Such as flammable and explosive chemical reagents, highly toxic chemical reagents, strong corrosive, strong oxidizing and other chemical reagents should be stored in a special dangerous reagent cabinet after receiving; special attention should also be paid when using, and some safety precautions should be taken in a targeted manner to avoid harm to experimental personnel and experimental equipment due to improper use. Let's talk about the management of chemical reagents in terms of the purchase, storage, storage and safe use of laboratory chemical reagents.
1. Collection of laboratory chemical reagents
(1) The collection of chemical reagents should be based on the experimental notice, and the laboratory administrator should prepare the required chemical reagents. General chemical reagents can only be collected after the subject teacher has gone through the registration procedures. Dangerous drugs and precious metal chemical reagents can only be received after the application of the teacher and the approval of the leader in charge.
(2) The number of chemical reagents received each time should be weighed by the laboratory administrator and promptly recorded on the gross weight label on the container for accounting purposes.
(3) When receiving a chemical reagent or drug, make sure that the name on the container is the required experimental drug. Pay attention to the drug hazard label and drawings to see if there is any harm. For your safety and the smooth progress of the experiment, please check the drug report (if any) and the safety data sheet (MSDS) of the reagent or drug.
(4) When receiving flammable and explosive, highly corrosive, strong oxidizing and other dangerous reagents, you must apply and report in advance, so that you can use as many as you want, and prepare them into reagents for use at one time. The distribution of highly toxic drugs is based on the principle of first-in, first-out, and accurate registration (measurement of reagents, distribution time and handlers) is issued. All highly toxic drugs must be collected by two people and returned by two people, otherwise the warehouse keeper of highly toxic drugs has the right not to distribute them.
2. Storage of laboratory chemical reagents
2.1 The storage of chemical reagents shall depend on their nature
General reagents can be stored in glass bottles; reagents that have a strong corrosive effect on glass, such as hydrofluoric acid and sodium hydroxide, should be stored in polyethylene plastic bottles; reagents that are easily oxidized, differentiated, and deliquescent by air should be sealed and stored; reagents that are susceptible to photodecomposition should be stored in colored glass bottles and hidden in the dark; reagents that are prone to thermal decomposition and low boiling point solvents should be stored in cold places; highly toxic reagents should be stored in safes; radioactive reagents should be stored in lead cans.
2.2 Do a good job in regular maintenance of chemical reagents
If chemical reagents are not properly stored, they will fail and deteriorate, affecting the effect of the experiment, causing waste of substances, and sometimes even accidents. Therefore, scientifically keeping reagents is of great significance to ensure the smooth progress of the experiment and obtain reliable experimental data. The deterioration of chemical reagents is mostly due to external conditions, such as oxygen in the air, carbon dioxide, water vapor, acid and alkali substances in the air, as well as ambient temperature, light, etc., which can cause chemical reagents to undergo oxidation, reduction, deliquescence, weathering, crystallization, dilution, rust, decomposition, volatilization, sublimation, polymerization, mildew, discoloration, and explosion. Regularly check the storage status of the chemical reagents in storage and find that the actual storage period or deterioration should be reported in a timely manner, and properly handled (downgraded or scrapped) and written off as required. Under normal storage conditions, the storage of general chemical reagents should not exceed 2 years, and the reference reagents should not exceed 1 year.
In order to avoid the interference of environmental and other factors, all chemical reagents shall not be put back into the storage container once they are taken out: reagents that must be recycled or designated or returned from storage must be recycled or stored in a special container. Chemical test reagents that are moisture-absorbing or easy to oxidize and perishable must be sealed and stored to avoid hygrolysis, oxidation or deterioration. Regular inventory, checking for errors should be checked in time and reported to the supervisor or department for handling.
3 Storage of laboratory chemical reagents
Chemical reagents should be stored in the reagent bottle, the lid of the bottle should be stuffed tightly, and placed firmly on the cabinet rack to ensure safety. And the placement should be neatly arranged and easy to use. All chemical reagents should be labeled, indicating the name, concentration and preparation time of the reagent solution. The size of the label should be suitable for the size of the reagent bottle, the handwriting should be clear, the font should be written correctly, and it should be glued to the middle part of the bottle slightly above, so that it is neat and beautiful. The label can be protected by molten paraffin wax. Special attention should be paid to safety when storing chemical reagents. The place where the reagents are placed should be cool, dry and well ventilated. Due to the variety of reagents, general reagents are classified and stored according to two categories: inorganic and organic substances. Special reagents and dangerous reagents are kept separately.
3.1 Storage of inorganic chemical reagents
Salts are stored separately according to the categories of salts, elements, oxides, bases, acids, etc. Salts are generally classified according to the position of metal ions in the periodic table, and also from left to right, the method of salting first and then acid salts: such as sodium salts - sodium sulfide, sodium carbonate, sodium silicate, sodium nitrite, sodium sulfate, sodium thiosulfate, calcium salts, etc. Elements are further divided into metals and non-metals or classified according to the groups of elemental elements in the periodic table. Oxides are also classified according to the order of the groups of the periodic table. Non-oxygenated acids in acids can be classified according to the groups of acid root elements in the periodic table from left to right, from top to bottom: such as hydrohalic acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, etc. Oxygen-containing acids can be classified according to the groups of acid-forming elements: boric acid, nitric acid, sulfuric acid, phosphoric acid, etc. Alkalis are mainly classified according to the groups of metal elements in the periodic table: such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, etc.
3.2 Storage of organic chemical reagents
Classified by functional groups: such as hydrocarbons (saturated hydrocarbons, unsaturated hydrocarbons), hydrocarbon derivatives (alcohols, aldodes, ketones, acids, ethers, esters), carbohydrates, nitrogenous compounds, organic molecular compounds, etc. Each reagent should be arranged in order of purity, and the prepared solution should be stored separately from the solid reagent.
3.3 Special attention: storage of dangerous chemical reagents
Hazardous chemical reagents Substances with high chemical activity, such as flammable and explosive reagents, corrosive reagents, toxic reagents, oxidizing reagents, radioactivity, and a series of "potent" chemical substances that are harmful to people and the environment, their "activity" is so high that they can even decompose on their own and threaten the safety of life and property, and must be taken seriously. According to relevant state regulations, the packaging of hazardous chemical reagents is marked with danger signs and dangerous regulations. There are also text descriptions in the relevant reagent manuals.
(1) Flammable and explosive chemical reagents must be stored in a dedicated hazardous reagent warehouse, and stored in cabinets and racks made of non-combustible materials. The temperature should not exceed 28 ° C. The "five pairs" system shall be implemented according to regulations. A small number of bottles in the laboratory can be equipped with dangerous goods counters, which can be stored according to the nature of the compartments. No contrasting products of oxidizer and other properties shall be mixed in the same compartment, and corresponding fire extinguishing equipment and automatic alarm devices shall be equipped according to the type of storage. Low boiling point highly flammable reagents should be stored at low temperatures (below 5 ° C, ordinary household refrigerators with electric sparks are prohibited from storage).
(2) Oxidative reagents should not be stored together with other reagents with conflicting properties. The packaging should be intact and sealed, and it is strictly forbidden to mix with acids. It should be placed in a cool and ventilated place to prevent sun exposure.
(3) Corrosive reagent storage containers must be selected according to their different corrosiveness. Acids should be kept away from cyanide, foaming agents, water-burning products, oxidants, etc., and should not be mixed with alkalis.
(4) Highly toxic reagents should be stored away from open flames, heat sources, oxidants, acids, and food products in good ventilation, generally not stored together with other types, and the "five pairs" system should be implemented as required.
(5) The flammable reagents in contact with water in chemical reagents must be stored in a warehouse that is dry, strictly prevent water leakage, and ensure that no water enters during heavy rain or flood. Do not store with items that emit acid mist such as hydrochloric acid and nitric acid, or mix with other dangerous goods.
In addition to the above three categories, there are other categories: such as indicators, acid-base indicator reagents, redox indicators, other indicators, stains, etc.; cleaning agents are classified as acidic chemical lotions, alkaline chemical lotions, other chemical lotions, and ordinary cleaning agents.
4 Precautions for the safe use of chemical reagents
The taken out reagent cannot be poured back into the original reagent bottle. After taking the reagent, it should be covered immediately and not placed indiscriminately to avoid wearing it. For the sake of safety, before using chemical reagents, first of all, it is necessary to have a comprehensive understanding of their safety performance - whether they are flammable and explosive, whether they are corrosive, whether they are toxic, whether they are strong oxidizing, etc. Only when using can some safety precautions be taken in a targeted manner to avoid improper use and harm to experimental personnel and experimental equipment. The following is an introduction to the precautions in the use of various chemical reagents from the safety performance classification of chemical reagents.
4.1 Flammable and explosive chemical reagents
Generally, chemical reagents with a flash point below 25 ° C are listed as flammable chemical reagents. Most of them are highly volatile liquids that can be burned in case of an open flame. The lower the flash point, the more flammable it is. When using flammable chemical reagents, you must never use an open flame, nor can you use a heater directly for heating. Generally, you do not need to use a water bath for heating. Experimenters who use flammable chemical reagents should wear the necessary protective gear and preferably wear protective glasses.
4.2 Toxic chemical reagents
General chemical reagents are toxic to the human body, and it is necessary to avoid inhalation in large quantities when using them. After using the performance reagents, you should wash your hands, wash your face, take a shower, and change your work clothes in time. For some chemical reagents that can be poisoned to death by inhalation or ingestion of a small amount, such as potassium cyanide, sodium cyanide and their cyanides; arsenic trioxide and certain arsenides, mercury dichloride and certain mercury salts, sulfuric acid, dimethyl ester, etc. When using these reagents, you must understand the first aid treatment methods when they are poisoned. Highly toxic reagents must be kept by a special person, and the amount used must be strictly controlled.
4.3 Corrosive chemical reagents
Any chemical reagents that touch the skin, mucous membranes, eyes, and respiratory organs should be cleaned up in time, especially those that are highly corrosive to the skin, mucous membranes, eyes, and respiratory organs, such as: various acids and bases, phosphorus trichloride, bromine, phenol, hydrazine, etc. Be sure to understand the first aid treatment methods for contact with these corrosive chemical reagents before use. For example, acid splashes on the skin should be cleaned with alkali, etc.
4.4 Strong oxidizing chemical reagents
Strong oxidizing chemical reagents are peroxidized to contain strong oxidizing ability of oxyacid and its salts. Such as: hydrogen peroxide, potassium nitrate, perchloric acid and its salts, potassium permanganate and its salts benzoic acid peroxide, phosphorus pentoxide, etc. Under appropriate conditions, oxygen can be released to explode, and explosive mixtures can be formed with organic matter, aluminum, zinc powder sulfur and other flammable substances. When using, the ambient temperature should not be higher than 30 ° C, and the ventilation should be good. Do not use (heat) with organic matter or reducing substances.
4.5 Flammable reagents in contact with water
This type of chemical reagent includes potassium, sodium, lithium, calcium, calcium carbide, etc. It can react violently in contact with water and emit a lot of heat. It can also burn. When using it, avoid direct contact with water and avoid contact with the human body to avoid burning the skin.
4.6 Radioactive chemical reagents
When using such chemical reagents, protective measures must be taken according to the method of using radioactive substances. Other types of dangerous chemical reagents, whether commonly used or not, must be aware of their safe use precautions before use.
In the process of chemical experiments, accidents will inevitably occur due to improper or negligent operation. The problem is to have a correct attitude and a cool head when encountering an accident. First, you must not panic. Second, you must deal with it correctly in a timely manner. Third, you must operate according to the requirements to avoid accidents. For example, when diluting concentrated sulfuric acid, the concentrated sulfuric acid should be slowly injected into water along the inner wall of the container, and stirred while adding it to spread the heat evenly. In the experiment of toxic gases, it should be carried out in a fume hood as much as possible. If you accidentally get phenol on your hands, you should immediately scrub with alcohol, rinse with water, etc.
In short, the management of chemical reagents must require managers to have professional knowledge of chemical reagent management. Including the properties, uses, general safety requirements, first aid measures, disposal of scrap reagents and fire protection knowledge of commonly used reagents. Strict management of chemical reagents can ensure the smooth progress of experiments, which is an important part of laboratory safety.
