Lead Fluoride, PbF₂

Lead Fluoride, PbF₂, is obtained as a white solid by the action of aqueous hydrofluoric acid on litharge or lead carbonate, or by precipitating the solution of a lead salt with a soluble fluoride. The heat of formation of this compound by the reaction Pb(OH)₂ + 2HF (gas) is 48,600 calories; it is easily fused to a yellow liquid, and has a density of 8.241. It is almost insoluble in water and aqueous hydrofluoric acid, but easily dissolves in hydrochloric and nitric acids. Its solubility in water at 18° C. has been deduced by Kohlrausch from the conductivity of its saturated solution. The specific conductivity of the salt is 431, and 1 litre of a saturated solution contains 640 milligrams. Although an aqueous solution of lead fluoride shows little evidence of hydrolysis, the solid salt is hydrolysed by water-vapour into hydrofluoric acid and a basic salt.

A chlorofluoride of lead, PbFCl or PbF₂.PbCl₂, was prepared by Berzelius by precipitating a solution of sodium fluoride with lead chloride. It may also be obtained from lead fluoride and ammonium chloride, and crystallises in quadratic plates. It is slightly soluble in water without decomposition. Various double salts of lead fluoride with other halides of the same metal have been prepared by Sandonnini.