The reaction of potassium fluoride with fuming sulfuric acid can produce fluorosulfonic acid. 40mL of fuming sulfuric acid (containing about 60% SO3) was added to a platinum or aluminum dish cooled by an ice-salt cold bath, and 20g of dried and crushed potassium hydroxide KHF2 was slowly added to the fuming sulfuric acid under stirring. This can form a sticky mass that gives off some smoke in the air. It is then slowly heated to 100 ° C to remove excess SO3 and HF. The product is placed in a Jena glass distillation unit with a ground joint, gradually heated to 250 ° C, and the HSO3F is distilled out. After secondary distillation, the obtained fluorosulfonic acid is very pure. 2. The reaction of chlorosulfonic acid with hydrogen fluoride can produce fluorosulfonic acid. A silver distillation flask with a silver drip funnel was used as the Chemicalbook as the reaction flask, and it was cooled in an ice salt bath. 50g of anhydrous HF was distilled from the gas outlet tube of the reaction flask to the reaction flask, and then a steel drying tube was connected at the end of the outlet tube, and the drying tube was filled with KF to absorb the HF carried out in the gas. When HSO3Cl is added from the drip funnel to the reaction bottle, the reaction begins immediately and there is a uniform release of HCl gas. At the end of the reaction, a stream of dry air is poured into the reaction bottle and slowly heated to 110 ° C to blow out excess HF and residual HCl. The remaining substance in the reaction bottle is HSO3F, which does not contain chlorine. Completely pure fluorosulfonic acid can be stored in burnt glass ampoules or in aluminium containers.