Potassium Fluoride: Hydrofluoric Acid Neutralised with Potassium Carbonate in Platinum (Roscoe 1913)

Hydrofluoric acid is neutralised with potassium carbonate in a platinum dish, which the acid cannot eat. The salt solution is then boiled down. Result: potassium fluoride. Above 40 °C it crystallises as anhydrous cubes; below 40 °C as prisms of the hydrate KF·2H2O. It melts at 885 °C and draws water from the air. Source: Roscoe and Schorlemmer, Treatise on Chemistry vol. 2 (1913), p. 329. Not given: amounts, acid strength, how neutrality is judged. Hydrofluoric acid burns deep and poisons through the skin. Picture drawn by Youblob.