How much do you know about hydrofluoric acid? Properties and uses of hydrofluoric acid

[alias] hydrofluoric acid

[Molecular formula] HF

[Properties] Hydrogen fluoride gas is easily soluble in water, and its aqueous solution is called hydrofluoric acid. Commercially available products are usually 35%-50% aqueous solution of hydrogen fluoride gas, the highest concentration can reach 75%, and it is a colorless and clear fuming liquid. It has a pungent odor, is volatile, and emits white smoke in the air. It is a medium-strength inorganic acid, highly corrosive, and can corrode glass and silicate to generate gaseous silicon tetrafluoride. It can also react with metals, metal oxides and hydroxides to form various salts, but the effect is not as severe as hydrochloric acid. Gold, platinum, lead, paraffin and some plastics do not work with it, so it can be used to make containers. Hydrogen fluoride gas is easy to polymerize to form chain molecules such as (HF)2(HF)3, etc. In liquid state, the degree of polymerization increases. Store in lead, wax or plastic containers. It is highly toxic and will fester on skin contact.

[Use] Used in the manufacture of sodium fluoride, aluminum fluoride, uranium hexafluoride, fluorocarbons, cryolite and other inorganic and organic fluorides. In the organic synthesis industry, it is used as an accelerator for polymerization, condensation and alkylation. Used as a catalyst in petrochemical industry. It is also used for engraving and engraving of glass instruments, utensils and mirrors, pickling of non-ferrous metals and stainless steel, desanding of metal castings, and treatment of frosted light bulbs. It is also used to make insecticides, fungicides, flame retardants, as well as electroplating, ceramic treatment, etc.

[Simplified method] There are two raw materials routes for the production of hydrofluoric acid: fluorspar and phosphate rock. The sulfuric acid method using fluorite as raw material is a method commonly used in industry. The dried fluorite powder and sulfuric acid are mixed according to the ratio of 1: (1.2-1.3), and hydrofluoric acid is obtained through pyrolysis, crude distillation, rectification and water absorption.

[Safety and Protection] Hydrofluoric acid is a Class I inorganic acid corrosive substance, hazard code number: 91035. Packed in polyethylene plastic bucket or tetrafluoroethylene plastic bucket. The net weight of each barrel is 20kg or 25kg. If the quantity is small, it can be packed in plastic bottles, 0.5kg per bottle, and the packaging should be marked with “highly toxic” or “corruptible items”. Do not store and mix with oxidants, organic matter, combustibles, alkali, metal powder, etc. In case of fire, yellow sand and carbon dioxide fire extinguishers can be used to extinguish it, and columnar water is prohibited.

Hydrofluoric acid is extremely corrosive, and its vapor is extremely poisonous. The maximum allowable concentration is 1mg/m3. In case of accidental contact with the skin, rinse immediately with plenty of water, or with 3% lye, 10% ammonium carbonate solution. Severe cases should be sent to hospital for treatment.