Introduction to the properties and uses of sulfuric acid

[Alias]Sulphurous water, sulfuric water.

[Molecular formula]H2SO4

[Properties]Pure sulfuric acid is a colorless, odorless oily liquid. Melting point 10.36°C (100%).

Handbook of Commonly Used Raw Materials in Fine Chemicals

Boiling point: 338°C (98.3%).

Density: 1.84g/cm3

It decomposes into sulfur trioxide and water at around 340°C. Commercially available sulfuric acid varies in purity, and its color ranges from colorless, yellow to reddish brown. Sulfuric acid is a strong inorganic acid. It can be arbitrarily mixed with water to form various solutions of different concentrations; when mixed with water, it will emit a lot of heat. Therefore, when diluting sulfuric acid, the sulfuric acid can only be slowly poured into cold water, and water must not be injected into the sulfuric acid, in case the surface of the acid liquid is overheated locally, and a large amount of heat energy has no place to radiate for a while, resulting in bumping, acid spray or explosion. ACCIDENT. Concentrated sulfuric acid has strong water absorption. When exposed to the air, the volume and weight will increase rapidly, so the container must be tightly closed. Concentrated sulfuric acid has a strong binding effect on water and can be used as a good desiccant and dehydrating agent; it can separate H and O elements from carbohydrates. Therefore, when fibers such as sucrose, paper, and cloth meet concentrated sulfuric acid, they can all be used It is carbonized and turned into black coke; it can also sulfonate or sulfate organic matter. Sulfuric acid is highly corrosive and oxidizing, and can form sulfate with almost all metals and their oxides and hydroxides. It can also be used with other Salt action of inorganic acids. Although iron cannot resist the action of dilute sulfuric acid, it has corrosion resistance to concentrated sulfuric acid. When there is no air at room temperature, cast iron can withstand the action of more than 62% sulfuric acid, and it can withstand more than 93% concentrated sulfuric acid even if it is above 100°C, so it can be shipped in iron drums. Lead has strong corrosion resistance to dilute sulfuric acid, but its resistance to concentrated sulfuric acid is poor.

［Applications］ Sulfuric acid is one of the important chemical products with large output and wide application in the chemical industry. It is widely used in chemical industry, fine chemical industry, light industry, textile, dyestuff, medicine, food, leather , metallurgy and other industries. Such as used in the manufacture of ammonium sulfate, calcium superphosphate, phosphoric acid, hydrofluoric acid, boric acid, aluminum sulfate, copper sulfate, zinc sulfate, ferrous sulfate and other chemical fertilizers, inorganic acids and sulfate products. Also used in acidification, sulfonation, catalysis, dehydration and other organic synthesis, used in the production of formic acid, oxalic acid, citric acid, benzoic acid, resorcinol, ethyl acetate and other products. In the textile dyeing and finishing industry, it can be used as cotton desizing agent, pickling agent, neutralizing agent, soluble vat dye developer, dyeing assistant, and carbonizing agent for removing wool impurities. Used in the petroleum refining industry to refine oil products and remove sulfides and unsaturated hydrocarbons in oil products. The pigment industry is used to manufacture titanium dioxide, lithopone, Hualan, etc. The leather industry is used to knead leather. In the pharmaceutical industry, it is used to produce salicylic acid, nitrofurazone, p-nitrochlorobenzene and pharmaceutical intermediates. Synthetic detergent industry is used to produce sodium alkylbenzene sulfonate, sodium tripolyphosphate, etc. In the metallurgical industry, it is used for the purification of various metal surfaces and the purification of rare metals. The dehydration of sulfuric acid can be used to preserve vegetables and grains. It can also be used for hard water softening, water quality treatment and as a catalyst in the production of starch glue, etc.

[Brief Recipe]

①The industrial production methods of sulfuric acid mainly include contact method and tower method (nitration method). The crude dilute sulfuric acid obtained by the tower method has a concentration of about 75%. Contact method can get 98.3% pure concentrated sulfuric acid. my country’s current industrial production all use the contact method. According to the different types of raw materials used, it can be divided into sulfur method, pyrite method, gypsum and phosphogypsum method, and smelting flue gas method.

②When preparing a small amount of pure concentrated sulfuric acid in the laboratory, an appropriate amount of potassium permanganate can be added to industrial sulfuric acid to remove some reducing impurities, then barium sulfide is added to remove potassium ions, and then obtained by distillation.

[Safety and Protection] Sulfuric acid is a first-class inorganic acid corrosive substance, hazard code number: 91007. It should be stored in a ventilated, cool and dry place, avoid the sun, strictly avoid water and moisture, and should not be mixed with oxidants, metal powders, oils, explosives, etc. In case of fire, yellow sand, mist water and carbon dioxide fire extinguishers can be used to put out the fire.

Sulfuric acid has a stimulating and burning effect on the mucous membrane of the respiratory tract and can damage the lungs. When the skin is touched, it must be washed with plenty of cold water as soon as possible, followed by a 2% soda solution. The amount of water used must be sufficient. If too little water is used to rinse the sulfuric acid, it will exacerbate skin burns due to the heat of dilution. If it splashes into the eyes, rinse it with water immediately, and then rinse with 2% boric acid solution, and send it to the hospital for treatment in severe cases.

Sulfuric acid with a concentration greater than 80% can be shipped in a tank truck made of steel plates, or packed in a ceramic jar and placed in a wooden box, filled with grass and other things around it, and the mouth of the jar is sealed with acid-resistant materials. It can be packed in glass bottles under 5kg, and there should be a sign of “corrosive substances” on the package.