Methods for storing hazardous reagents or chemical hazards

This post was last edited by fengxuemei on 2009-9-1 16:05. Storage and Use of Common Chemical Reagents I. Classification of Chemical Reagents There are various methods for classifying reagents. Based on their state, they can be divided into solid reagents and liquid reagents. Based on their use, they can be divided into general reagents and specialty reagents. They can be classified into inorganic reagents and organic reagents. Based on performance, they can be classified as hazardous reagents, non-hazardous reagents, etc. From the perspective of reagent storage and use, reagents are often classified in two ways: by category and by performance. (1) Inorganic reagents and organic reagents: This classification method is consistent with the classification of chemical substances, which facilitates identification and memorization as well as storage and retrieval. Inorganic reagents are first classified into major categories such as elements, oxides, bases, acids, and salts, and then further classified based on their properties. Organic reagents are classified into hydrocarbons, hydrocarbon derivatives, sugars and proteins, polymers, indicators, etc. (II) Hazardous and non-hazardous reagents: This classification takes into account both practicality and the characteristic properties of the reagents. Therefore, it facilitates both safe storage and compliance with safety procedures by laboratory personnel when in use. 1. Classification of hazardous reagents: Based on the properties of these reagents and their storage requirements, they are classified as follows: (1) Flammable reagents. These are chemical substances that can catch fire on their own in air or easily ignite when in contact with other substances. Depending on their state or the causes that lead to combustion, they can generally be classified as: ① Self-igniting reagents: such as yellow phosphorus. ② Water-reactive chemicals: such as potassium, sodium, calcium carbide, etc. ③ Flammable liquid reagents: such as benzene, gasoline, ether, etc. ④ Flammable solid reagents, such as sulfur, red phosphorus, aluminum powder, etc. (2) Explosive reagents refer to chemical substances that undergo violent chemical reactions upon exposure to external forces, resulting in combustion and explosion while releasing large amounts of harmful gases. Such as potassium chlorate, etc. (3) Toxic reagents refer to chemical substances that have a strong toxic effect on humans or organisms, as well as on the environment. Such as bromine, methanol, mercury, arsenic trioxide, etc. (4) Oxidizing agents refer to substances that can oxidize other materials while being reduced themselves, such as sodium peroxide, potassium permanganate, ammonium dichromate, *ao acid an, etc. (5) Corrosive reagents refer to chemical substances with strong corrosiveness that can cause damage to the human body and other items through corrosion, and may even lead to combustion, explosion, or injuries, such as strong acids, strong bases, anhydrous aluminum chloride, formaldehyde, phenol, hydrogen peroxide, etc. 2. Classification of non-hazardous reagents Based on their properties and storage requirements, non-hazardous reagents can be divided into: (1) Reagents that deteriorate easily when exposed to light – these are substances that, under the influence of ultraviolet light, tend to cause the reagent itself to decompose or to undergo chemical reactions with components in the air. Such as nitric acid, silver nitrate, ammonium sulfide, ferrous sulfate, etc. (2) Reagents that deteriorate easily when exposed to heat. Such reagents are mostly biological products and unstable substances; they can undergo decomposition, mold formation, or fermentation at high temperatures, and some do the same at room temperature as well. Such as *ao acid an, ammonium carbonate, agar, etc. (3) Reagents that freeze easily: These reagents have melting or freezing points within the range of temperature fluctuations. When the temperature is above their melting point, or drops below their freezing point, the reagents expand or contract in volume as a result of melting or freezing, which can easily cause the reagent bottles to crack. Such as glacial acetic acid, crystalline sodium sulfate, crystalline sodium iodate, and aqueous solutions of bromine, etc. (4) Weathering-prone reagents: These reagents contain a certain proportion of crystal water and are usually in crystalline form. At room temperature in dry air (with a relative humidity generally below 70%), it can gradually lose some or all of its crystalline water and turn into a powder. It is difficult to determine its content when in use. Such as crystalline sodium carbonate, crystalline aluminum sulfate, crystalline magnesium sulfate, bluestone, alum, etc. (5) Deliquescent reagents: These reagents readily absorb moisture from the air, leading to deliquescence, deterioration, changes in appearance, reduced content, and even mold growth. Such as ferric chloride, anhydrous sodium acetate, methyl orange, agar, reduced iron powder, aluminum-silver powder, etc. II. Grade standards for chemical reagents Upon entering a chemistry laboratory, one can see a variety of reagent bottles, each labeled with the name of the reagent contained within, to facilitate its use. And the tags have different colors – is that for decoration? Upon closer inspection, in addition to the name and molecular formula printed on the label, there are symbols such as CP and AR – what do these mean? It turns out that chemical reagents are classified into different grades based on the amount of impurities they contain, in order to meet various needs. To enable quick selection of the required reagent among various different grades of the same reagent, it is also specified that reagents of different grades are labeled in different colors. At present, the specifications of reagents in our country are generally divided into 5 grades; the lower the grade number, the higher the purity of the reagent. Grade 1 pure: Used for precision chemical analysis and research work; also known as guaranteed reagents. The symbol is GR, and the label is green. Grade 2 pure: Used for analytical experiments and research work; also known as analytical grade reagents. The symbol is AR, and the label is red. Grade 3 pure: Used for chemical experiments, also known as chemically pure reagents. The symbol is GP, and the label is blue. Grade 4 pure: Used for general chemical experiments, also known as experimental reagents. The symbol is LR, and the label is yellow. Industrial grade: an industrial product that can also be used for general chemical experiments. Symbol TP. However, in recent years, the color of the labels corresponding to the reagent grade has become less accurate. Therefore, it should mainly be selected based on the level and symbols indicated on the label. For the same reagent, different purities result in different specifications, and the prices vary significantly. Therefore, it is necessary to select reagents of appropriate specifications based on the experimental requirements, in order to ensure satisfactory experimental results while preventing waste. There are over 100 reagents required for middle school chemistry experiments, of which more than 70% are of grade 4 purity. A small amount of several grades of secondary purity and tertiary purity are used, with the rest being industrial-grade products. III. Handling of Chemical Reagents: In the laboratory, only solid and liquid reagents are generally stored, while gaseous substances are prepared on demand. When handling and using any chemical reagents, it is essential to follow the \"three don’ts\": do not touch them with your hands, do not smell them directly, and do not taste them. It should also be noted that after opening the reagent bottle stopper or cap, it should be placed upside down on the table, and the stopper should be reinserted tightly immediately after taking the reagent. Otherwise, it will contaminate the reagents, causing them to deteriorate and become unusable, and may even lead to accidents. (1) Handling of solid reagents: Powdered or granular reagents are generally handled using a spatula. Medicine spoons come in animal-horn versions as well as plastic ones, and they vary in size. For those that require a larger amount and have a bigger container diameter, a large medicine spoon can be chosen ； For smaller amounts or containers with a narrow mouth, a small spoon can be used, and it should be inserted as far as possible to the bottom of the container. In particular, powdered reagents tend to scatter easily. Or stick to the mouth and walls of the container. It can be poured onto a folded trough-shaped strip of paper; then the container is placed flat so that the paper trough extends along the container walls to the bottom. The container is raised and the paper trough is shaken gently, causing the reagent to fall to the bottom of the container. When using forceps to insert the solid mass into the container, be sure to tilt the container first so that it can slide slowly down to the bottom along the walls of the container. If no specified dose is given in the experiment, the amount of sample to be used should be just enough to cover the bottom of the test tube. Excess reagent cannot be put back into the original bottle nor discarded; it should be placed in a designated container for use by others or in a future occasion. The forceps or spatula used to take reagents must be wiped clean, and under no circumstances should the same spatula be used multiple times. It should also be wiped clean after use, leaving no residue. (II) Handling of liquid reagents: When a small amount of liquid reagent is needed, a dropper is commonly used for picking it up. When a larger amount is used, the pouring method is employed. When pouring the liquid from a narrow-mouthed bottle into a container, hold the side of the reagent bottle with the label in the palm of your hand; use the other hand to hold the container at an angle so that the bottle’s opening is in contact with the container’s opening, then gradually tilt the bottle to pour out the reagent. The reagent should flow into the container along its wall, or the liquid reagent can be introduced into a narrow-mouthed or flat-bottomed container using a clean glass rod. After removing the desired amount, gradually raise the reagent bottle and let the remaining droplets at the mouth of the bottle fall into the container, so as to prevent the droplets from flowing down the outer wall of the reagent bottle. If no specified dose is given in the experiment, 1 to 2 mL is generally used. For quantitative use, a pipette, burette, or volumetric pipette can be selected as required. Excess reagent cannot be poured back into the original bottle, nor can it be discarded carelessly. It should be poured into the designated container for others to use. When using toxic reagents, it must be done under the supervision of a teacher, or in strict accordance with the rules. (III) Use of indicators: Indicators are used to determine the acidity or alkalinity of substances, to measure the pH of solutions, or in volumetric analysis to indicate the attainment of the equivalence point. Indicators are generally organic weak acids or weak bases; they change color sensitively within a certain pH range, making them easy to observe. Therefore, its amount used is very small; generally, 1 drop of indicator is added to every 10 mL of solution. There are many types of indicators; in addition to the well-known litmus, phenolphthalein, and methyl orange, there are also methyl red, thymolphthalein, thymol blue, bromocresol green, and so on. They have different color-changing ranges and varying applications. In volumetric analysis, for certain specific requirements, mixed indicators are often used in addition to single indicators. Below are some commonly used indicators along with their color change ranges (see Table 2-1). Indicators are used to determine the acidity or alkalinity of solutions, and they are also often employed to test the acidity or alkalinity of gaseous substances. Therefore, in experiments, two types are commonly used: indicator solutions and test strips. When using the test solution, generally 1–2 drops of it are added to the liquid to be tested using a dropper, and after shaking, the change in color is observed. When using the test strip, under no circumstances should it be placed in or inserted into the solution to be tested. Only a clean glass rod can be used to drop the dipped sample solution onto the center of the test strip placed on a slide, in order to observe the color once it has stabilized. When using a pH test strip to determine the acidity or alkalinity of a solution, the strip must not get wet; half a minute after dropping the sample solution on it, its displayed color should be compared with a standard color chart to obtain the result. Test strips cannot be used to directly determine the acidity or alkalinity of substances with strong dehydrating properties such as concentrated sulfuric acid. Table 2–1 Indicators, Color Change Range, pH, Color Change, Concentration, Amount Used (drops per 100 mL of sample solution)
Methyl orange: 3.1–4.4, Red–Yellow; 0.05% aqueous solution, 1 drop
Bromophenol blue: 3.0–4.6, Yellow–Purple; 0.1% solution in 20% ethanol or its sodium salt solution, 1 drop
Bromocresol green: 4.0–5.6, Yellow–Blue; 0.1% solution in 20% ethanol or its sodium salt solution, 1–3 drops
Methyl red: 4.4–6.2, Red–Yellow; 0.1% solution in 20% ethanol or its sodium salt solution, 1 drop
Litmus: 5.0–8.0, Red–Blue; 0.05%–1% aqueous solution, 1–3 drops
Phenolphthalein: 8.0–10.0, Colorless–Red; 0.05% solution in 90% ethanol, 1–3 drops
Bromothymol blue: 8.0–9.6, Yellow–Blue; 0.05% solution in 90% ethanol, 1–4 drops
Bromophenol purple: 9.4–10.6, Colorless–Blue; 0.05% solution in 90% ethanol, 1–2 drops
To test the properties of volatile substances such as acidity, alkalinity, oxidizing ability, or reducing ability, the test strip can first be moistened with distilled water, then suspended above the mouth of a container or an exhaust pipe using a glass rod, so that the color change of the strip after being exposed to the substance can be observed. Indicators each have their own color-change range, but this range is not exactly around pH 7. Secondly, various indicators exhibit gradually changing transition colors within their color-changing range. Furthermore, the range values of color change for various indicators also vary. Therefore, in acid-base neutralization titrations, in order to reduce errors at the endpoint, appropriate indicators should be selected for different types of acid-base titrations. Generally, when a strong acid is titrated with a strong base or vice versa, methyl orange, methyl red, or phenolphthalein solution can be used as an indicator ； When a strong base is used to titrate a weak acid, thymolphthalein or thymol blue solution should be chosen as an indicator; whereas when a strong acid is used to titrate a weak base, bromocresol green or bromophenol blue solution should be used. Some of the specific reagents commonly used in experiments are hazardous, some tend to deteriorate easily, and others have multiple property parameters; carelessness with them can lead to accidents. IV. Storage and Use of Some Special Reagents (I) Flammable Solid Reagents 1. Yellow Phosphorus Yellow phosphorus, also known as white phosphorus, should be stored in a brown wide-mouth bottle filled with water, the water level having to cover the phosphorus completely ； Then bury the reagent bottle in a metal can or plastic tube filled with silica. When used, it is prone to oxidation, has a low ignition point, is highly toxic, and can burn the skin. Therefore, it should be grasped with forceps underwater and cut off with a small knife. All the fallen fragments must be gathered up to prevent them from scattering. 2. Red phosphorus, also known as erythrophosphorus, should be stored in a brown wide-mouth bottle and must be kept dry. Use a spoon when taking it; keep it away from sources of fire and avoid contact with hot objects. 3. Sodium, Potassium: Metal sodium and potassium should be stored in wide-mouth bottles filled with anhydrous kerosene, liquid paraffin, or toluene, with the bottle openings sealed tightly with stoppers. If a cork is used, it also needs to be sealed with paraffin. Do not let it come into contact with water or solutions when retrieving it, as this can easily cause a fire. The method of use is similar to that of white phosphorus. (II) Reagents that easily release corrosive gases 1. Liquid bromine: Liquid bromine has a high density and is highly volatile; its vapors are extremely toxic, and contact with bromine on the skin can cause burns. Therefore, liquid bromine should be stored in sealed brown ground-glass flasks; to prevent its diffusion, water is usually added on top of the bromine liquid to act as a seal. Then, seal the reagent bottle of liquid bromine tightly in a plastic tube and place it in a cool area where it cannot be knocked over. When taking it, use a dropper to dip it under the surface of the liquid bromine, quickly draw up a small amount, and then seal it before returning it to its original place. 2. Concentrated helium water: Concentrated ammonia water is highly volatile; it should be stored in brown flared-mouth bottles with plastic stoppers and screw caps, in a cool place. When using it, be very careful when opening the bottle cap of concentrated ammonia. Due to the high gas pressure inside the bottle, it is possible for the liquid ammonia to be forced out of the bottle opening and spill. Therefore, use plastic film or similar to cover the bottle opening so that it is not facing anyone, and then open the stopper. Especially in the hot summer months, it can be cooled with cold water first before being used. (3) Concentrated hydrochloric acid: Concentrated hydrochloric acid readily releases hydrogen chloride gas, which has a strongly irritating odor. Therefore, it should be stored in a ground-glass flask in a cool place, away from concentrated helium solutions. When taking or preparing solutions of such reagents, if the amount is large and the contact time is long, a gas mask should also be worn. (III) Flammable liquid reagents: Ethanol, ether, carbon disulfide, benzene, propanol, etc., have very low boiling points; they are highly volatile and prone to catching fire. Therefore, they should be stored in brown flared bottles equipped with both plastic stoppers and screw caps, and kept in a cool place. Do not approach open flames when using it. Often, a small amount of heavy water is poured into the carbon disulfide bottle to serve as a \"water seal.\" Since carbon disulfide has an extremely low boiling point of 46.3°C, a density greater than that of water at 1.26 g/cm3, and is insoluble in water, storage under a water seal prevents volatilization. Adding a small amount of copper wire to the ether flask is used to prevent ether from forming explosive peroxides as a result of degradation. (IV) Sublimable substances There are various sublimable substances, such as iodine, dry ice, naphthalene, anthracene, benzoic acid, etc. After the iodine tablets sublimate, their vapor is corrosive and toxic. Therefore, such solid substances should all be stored in brown wide-mouth bottles, sealed and kept in a cool place. (5) Highly toxic reagents: Commonly encountered highly toxic reagents include cyanides, arsenides, mercury compounds, lead compounds, soluble barium compounds, as well as mercury and yellow phosphorus. Such reagents need to be kept separate from acidic substances, in a dry and cool place, in a locked cabinet. It should be used under guidance. When a small amount of mercury is needed for experiments, it can be drawn up using a dropper that functions as a capillary. If mercury accidentally spills on the floor, a zinc sheet coated with hydrochloric acid can be used to collect it; mercury forms an amalgam with zinc, and after the zinc is dissolved using hydrochloric acid or dilute sulfuric acid, the mercury can be recovered. The trace amounts of mercury remaining on the ground should be removed by covering them with sulfur powder or by sprinkling ferric chloride solution; otherwise, mercury vapor remaining in the air can cause harmful accidents. (VI) Prone-to-degradation reagents 1. Solid caustic soda: Sodium hydroxide absorbs moisture very easily and also absorbs carbon dioxide from the air, which causes it to degrade and become unusable. Therefore, it should be stored in a wide-mouth bottle or plastic bottle, with the lid sealed with wax. Special care should be taken to avoid using glass fortresses to prevent sticking. Potassium hydroxide is the same. 2. Alkali lime, quicklime, calcium carbide (calcium carbide), phosphorus pentoxide, sodium peroxide, etc. The aforementioned reagents are prone to deterioration when reacting with water vapor or carbon dioxide, and they should all be stored in sealed conditions. Especially after use, make sure to tighten the bottle cap and store it in a dry place. 3. Ferrous sulfate, sodium sulfite, sodium nitrite, etc. The aforementioned reagents possess strong reducing properties and are prone to oxidation by oxygen in the air, resulting in deterioration. It should be stored in a sealed condition to minimize contact with air. 4. Hydrogen peroxide, silver nitrate, potassium iodide, concentrated nitric acid, ferrous salts, trichloromethane (chloroform), phenol, aniline, and other such reagents deteriorate when exposed to light; some of them also release toxic substances. They should all be stored in separate brown reagent bottles according to their state, and direct light should be avoided. V. Home preparation and substitution of chemical reagents: The reagents used in chemical laboratories are typically purchased as complete sets as required, or additional reagents are acquired on an ad-hoc basis from chemical supply stores or specialty reagent shops. If certain reagents needed for an experiment are not available immediately, we can utilize reaction principles to select appropriate alternative reagents and assemble the necessary equipment through simple home preparation based on the experimental procedure. One can either conduct interesting home chemistry experiments using various substances available at home, or use easily obtainable waste materials or raw materials to create useful reagents through simple methods. This will undoubtedly be of great benefit to everyone in strengthening their knowledge of chemistry, broadening their horizons, and developing their practical skills. It will also make us fall in love with natural sciences even more, thereby inspiring us to dedicate ourselves to scientific pursuits. (1) Substitution of reagents: Many of the chemical reagents used in laboratories are also suitable for industrial, pharmaceutical, and medical applications. If some physical and chemical properties are altered, it can even be used directly in the food industry. Conversely, substitutes for some of the reagents required in the laboratory are certainly easy to find to meet the experimental requirements. Below are some substitutes for reagents. Everyone should pay close attention and stay vigilant, so as to be able to find more inexpensive and suitable substitutes. (See Table 2-2) Table 2-2: Substitutable Reagents. Reagent | Substitute Zinc | Shells of used dry batteries Aluminum | “Aluminum-silver powder” used in paint, aluminum foil from cigarette packs, insulation cores for electrical wires Copper | Copper wire cores Sulfur | Household sulfur Iodine | Medical iodine tincture Calcium oxide | Quicklime used in construction Calcium hydroxide | Lime slurry used in construction wash tanks Iron oxide | Iron red (also known as ferrous oxide or red lead) used in paint Sodium bicarbonate | Pharmaceutical soda tablets, edible baking soda Sodium carbonate | Soda ash Sodium thiosulfate | Industrial baking soda, fixing agent Potassium permanganate | Pharmaceutical manganese permanganate or potassium permanganate tablets Potassium nitrate | Fireworks-grade nitrate Calcium sulfate | Pharmaceutical gypsum, gypsum used to make tofu Calcium carbonate | Limestone, calcite used in construction, scale from pots, eggshells Copper sulfate crystals | Agricultural blue vitriol Sodium sulfate | Pharmaceutical mirabilite Potassium aluminum sulfate | Commercially available alum Mercury oxide | Pharmaceutical Sanxiandan Phenol | Pharmaceutical carbolic acid Formaldehyde | Commercially available formalin Acetic acid | Vinegar Glycerol | Commercially available glycerin Fructose | Used to dissolve hard candies Maltose | Syrup sugar, white rock sugar Starch | Commercially available bean flour, rice water Polyethylene | Food packaging bags Polyvinyl chloride | Colored outer coatings for various wires (II) Preparation of Reagents 1. Preparation of bromine Ingredients: 10 g of sodium bromide, 4 g of manganese dioxide, 6 mL of concentrated sulfuric acid. Principle: 2NaBr + MnO2 + 2H2SO4 → Na2SO4 + MnSO4 + Br2 + 2H2O. Diagram of the setup: After mixing sodium bromide and manganese dioxide evenly, they are placed in an 18×180 mm test tube, after which concentrated sulfuric acid is added. Assemble all the instruments as shown in the diagram, then heat the mixture until no more reddish-brown gas is produced. A small amount of liquid bromine can be obtained in the U-tube, while bromine water is obtained in the reagent bottle filled with water. Pour out the liquid bromine and store it in the proper manner. Seal the flask containing bromine water with a ground glass stopper, label it separately, and set it aside for use. 2. Production of iodine Materials: 0.5 g of potassium iodide, 0.2 g of manganese dioxide, 1.5 mL of concentrated sulfuric acid. Principle: 2KI + MnO2 + 2H2SO4 → K2SO4 + MnSO4 + I2 + 2H2O. Diagram of the setup: Use two test tubes of different sizes; the smaller test tube is fixed to cardboard and then placed inside the larger test tube. As shown in the figure below. Preparation: Mix potassium iodide and manganese dioxide and place them in a large test tube; add concentrated sulfuric acid to it. Add about half cold water to a small test tube for condensing the vapor, then heat the reactants gently. Purple vapor is produced in the large test tube, and iodine condenses on the outer wall of the small test tube, which is then collected for use. 3. Production of sodium hydroxide: Raw materials: soda ash, slaked lime (the amount used is determined by the desired output). Principle: Na2CO3 + Ca(OH)2 → CaCO3↓ + 2NaOH. This method is also known as the causticization process for producing caustic soda. Production: First, prepare a water solution of soda ash at about 12% concentration; then add slaked lime in an amount equal to 60% of the amount of soda ash used. Heat the mixture in an iron pot, maintaining the reaction temperature between 80°C and 100°C, while stirring continuously for about 2 hours. Slightly cold; filter out the precipitate. The filtrate is an approximately 10% sodium hydroxide solution with a density of about 1.1 g/cm3. Reheating and evaporating to dryness yields solid caustic soda. Its raw materials can be replaced with industrial substitutes. Similar to this method, by replacing soda ash with potassium carbonate, potassium hydroxide can also be produced manually. 4. Preparation of soda lime. Soda lime is a commonly used desiccant in laboratories, and it is also an essential raw material for producing ammonia or methane in the lab. Raw materials: quicklime, caustic soda. Preparation: Place 1 part of a saturated caustic soda solution in an iron or ceramic evaporation dish, then add 2 parts by mass of quicklime. Mix thoroughly, heat while stirring until it evaporates completely, and then bake for about 2 minutes. Take it out, grind it, seal it in a bottle, and place it in a desiccator for later use. The newly prepared alkali lime works particularly well when heated together with anhydrous sodium acetate to produce methane. 5. Preparation of potassium chlorate: Place 30 g of solid potassium hydroxide in a conical flask or beaker, add 70 mL of distilled water, stir, and gradually introduce chlorine gas while the mixture is still hot (above 75°C) (make sure to do this in a fume hood), until crystals begin to form. During static cooling, a larger amount of potassium chlorate crystals will precipitate out in the container. This is due to the following reaction: 3Cl2 + 6KOH → 5KCl + KClO3 + 3H2O. At low temperatures, the solubility of potassium chlorate is lower than that of potassium chloride, so potassium chlorate can be produced using this method. After treatment, the mother liquor mentioned above can be used as a KCl solution for general experiments and must not be discarded. 6. Preparation of ferrous sulfate: Take about 15 g of iron filings in a beaker, add 100 mL of water, and then add 10 mL of concentrated sulfuric acid in several portions; gas is observed to be released slowly during this process. Heat the liquid until no more bubbles are formed; once half of the solvent has evaporated, place the beaker on an asbestos net and filter it while it is still warm. Add a few sections of stripped silk to the filtrate, cover the beaker with a watch glass, and upon cooling, ferrous sulfate crystals (FeSO4•7H2O) will precipitate. The mother liquor is an iron(II) sulfate solution; after adding a small amount of dilute sulfuric acid and milling chips, it is transferred to a reagent bottle for storage until use. 7. Preparation of basic copper carbonate: In a 500 mL beaker, add a 1 mol/L copper sulfate solution; while stirring, add a 1 mol/L sodium carbonate solution, testing with red litmus paper at each addition until the red paper turns blue. Filter by suction using a Büchner funnel and a filter flask. The precipitate is washed several times with distilled water until the filtrate tests negative for copper chloride; thereafter, the precipitate is removed, dried first with filter paper and then air-dried (without heating), to yield basic copper carbonate with a beautiful peacock green color. 8. Preparation of catalysts: In various experiments conducted in industrial production or in the laboratory to study the principles of industrial production, catalysts are often used to accelerate reaction rates. And in order to improve the activity of the catalyst, it is often used attached to various “supports”. Using substances that are easily available in the laboratory to create a \"carrier-catalyst\" not only meets the requirements of experiments but also serves as an effective substitute for expensive and hard-to-find materials such as platinum and rhodium. A carrier is a stable material that can disperse the catalyst, possesses a large surface area, and has certain strength. Such as pickled asbestos fluff, pumice, diatomaceous earth, refractory bricks, alumina, clay, silica gel, activated carbon, and even broken porcelain pieces, as well as burned animal ashes. All can serve as carriers to disperse the catalyst. Below are several carriers-catalysts that offer good performance, wide applicability, and simple preparation methods, provided for reference when manufacturing. (1) Asbestos-silver catalyst: Take a clean small beaker (50 mL) and fill it with 20 mL of 2% silver nitrate solution. Add 2% dilute ammonia solution drop by drop to the beaker, stirring continuously; once the brown precipitate has just disappeared, add 3–5 additional drops of dilute ammonia to prepare the silver ammonia solution. Add 2 mL of 10% glucose solution to this silver-ammonia solution, stir with a spoon, then add a small amount of asbestos fluff as a carrier into the beaker so that it is completely submerged in the solution. Heated in a water bath, after a few minutes, the color of the solution darkened; silver deposits could be clearly seen on the walls of the beaker until a shiny layer formed, at which point the silver was also deposited on the carrier. Pour off the solution, rinse the catalyst 2–3 times with distilled water, squeeze out the excess water first, and then place it on an asbestos mesh to dry using an alcohol lamp or an electric heater. The asbestos-silver catalyst can be used in various experiments, including the contact oxidation of sulfur dioxide, the catalytic oxidation of ammonia, and the oxidation of lower alcohols to aldehydes. (2) Asbestos-chromium trioxide catalyst: Soak a small amount of asbestos in a saturated solution of ammonium dichromate or in a mixture of potassium dichromate and ammonium chloride. Once the maximum amount of adsorption has been reached, remove it and burn it on an iron wire mesh until its surface turns green (until no more gas is produced), at which point the catalyst is ready. Its range of application is the same as that of asbestos-silver. (3) Asbestos-iron catalyst: Soak a small amount of asbestos in a saturated ferric chloride solution for about 5 minutes to achieve maximum adsorption. The asbestos is removed and placed on a wire mesh; it is then heated using an alcohol lamp or an electric furnace until its surface turns red-brown. Subsequently, hydrogen is passed over it to reduce it to black iron (i.e., reduced iron). It is suitable for ammonia synthesis. By replacing asbestos with other carriers, catalysts with different carriers can also be created. A simpler method is to mix asbestos with ready-made powdered chromium trioxide or manganese dioxide, etc., and use it directly, which also yields quite good results. If we are observant and willing to use our brains, we can also utilize used dry batteries and broken thermos flasks to create various useful reagents or substances. One of the uses of chemistry is precisely to utilize waste and turn it into something valuable. 9. Preparation of simple indicators: In the laboratory, acid-base indicators such as litmus and phenolphthalein are commonly used. We can also use the pigments in plants to create various simple indicators on our own, by taking advantage of the color changes they undergo in acidic and alkaline solutions, across different natural seasons. The method of preparation is as follows: The collected fresh flowers or other plant parts have their stamens removed, and their petals are cut off. After being washed with water, they are ground into a paste in a mortar. Alcohol or liquor is then added to soak it for a period of time, after which an appropriate amount of distilled water is added to achieve a certain color (referred to as the original solution color). Once filtered, the filtrate can be used to roughly determine the acidity or alkalinity of the solution. However, simple indicators are prone to variation, so they should be stored sealed in brown bottles.

Grades of general chemical reagents: Grade 1 reagents, Grade 2 reagents, Grade 3 reagents, Grade 4 reagents. Domestic standard names: Reagent Grade A (guaranteed reagent), Analytical grade, Chemical grade, Experimental reagent. Domestic abbreviation codes: GR AR CP LR. Domestic label colors: green, red, blue, medium yellow. Purity and applications: High purity with low impurity content; suitable for research and the preparation of standard solutions ； It has a high purity and low impurity content, making it suitable for qualitative and quantitative analysis. Its weight is slightly less than that of grade 2 reagents, and its uses are similar to those of grade 2 reagents. . Chemical reagents can be classified into various grades based on purity, ranging from industrial grade to ultra-pure grade, including industrial pure, laboratory reagent grade (L.R.), chemical pure (C.P.), analytical pure (A.R.), high-purity grade (G.R.), and ultra-pure grade. The methods of preserving substances are related to their physical and chemical properties. When storing chemical reagents, laboratories should generally follow these guidelines: Sealing. Most reagents need to be stored in sealed containers, and this is an important principle for storing reagents in a laboratory. The prominent categories are as follows: ① Volatile reagents, such as concentrated hydrochloric acid, concentrated nitric acid, concentrated bromine water, etc. ②Reagents that readily react with water vapor and carbon dioxide, such as anhydrous calcium chloride, sodium hydroxide, water glass, etc. ③Reagents that are easily oxidized (or reducing agents), such as sodium sulfite, hydrosulfuric acid, ferrous sulfate, etc. Protect from light: Reagents that are prone to decomposition when exposed to light or heat should be kept away from light and stored in a cool place. Substances such as nitric acid and silver nitrate should generally be stored in brown reagent bottles. Corrosion protection: For reagents that have a corrosive effect, it is necessary to take precautions against corrosion. If hydrofluoric acid cannot be stored in a glass bottle ； Strong oxidizers and organic solvents should not be stored in reagent bottles with rubber stoppers ； Alkaline solutions, water glass, etc. should not be stored in reagent bottles with glass stoppers. Inhibition: For reagents that are prone to hydrolysis or oxidation, certain substances must be added to inhibit their hydrolysis or oxidation. For example, a small amount of hydrochloric acid is often added to iron chloride solutions ； A small amount of iron filings is often added to ferrous sulfate solutions. Isolation: Flammable organic materials should be kept away from sources of fire ； Strong oxidizing agents (peroxides or oxygen-containing acids with strong oxidizing properties and their salts) should be stored separately from substances that are easily oxidized (toner, sulfides, etc.). Ventilation: This principle should be followed when storing most reagents. In particular, flammable organic substances, strong oxidizers, etc. Low temperature: For reagents that are prone to reacting at room temperature, measures should be taken to store them at low temperatures. Unsaturated hydrocarbons and their derivatives such as styrene and methyl acrylate tend to polymerize at room temperature, and hydrogen peroxide decomposes easily; therefore, they must be stored in an environment below 10°C. Special: Special reagents require special measures for storage. Substances such as potassium and sodium should be placed in kerosene, while white phosphorus should be placed in water ； Liquid bromine is highly volatile, so it needs to be covered with a layer of water or something similar. Most reagents in the laboratory have multiple properties, and various factors must be taken into account when storing them, in accordance with relevant principles.