Mercury(I) fluoride or mercurous fluoride, Hg2F2, consists of small yellow cubic crystals, which turn black when
exposed to light. Mercury(I) fluoride is formed by the reaction of mercury(I) carbonate with hydrofluoric acid.
Hg2CO3 + 2HF→Hg2F2 +CO2 +H2O
small, yellow cub crystal(s); blackens in light; preparation by reaction of Hg2CO3 and HF [MER06]
Mercury(I) fluoride is used as antiseptic. It is used in the Swarts reaction to convert alkyl halides into alkyl fluorides.
The wet Hg2CO3 is added in small portions and with
constant stirring to 40% hydrofluoric acid solution contained in a
platinum dish. A yellow powder of Hg2F2 settles out. The addition of Hg2CO3 is continued as long as CO2 is vigorously evolved;
the highly dilute supernatant hydrofluoric acid is then poured off
and a new portion of 40% hydrofluoric acid solution is added. The
resulting mixture is evaporated to dryness on a water bath. The
product is then pulverized and heated for 2-3 hours in a drying
oven at 120-150°C. The product is then immediately poured into
copper containers and vacuum-sealed.
