Manufacture of synthetic cryolite with - reduced ignition loss

摘要

Manufacture of synthetic cryolite with reduced ignition loss To avoid the necessity of high temp. calcination before use in electrolytic Al reduction, synthetic cryolite is repulped in an aqs. soln., pH 4, pref. 1-2, contg. HCl, HNO3, HF or H2SO4 for at least 10 mins. below the b.pt. of the aqs. soln., pref. at 50-95 degrees C, using 1-20 pts aqs. acid soln. per pt. cryolite. The aqs. soln. opt. contains up to 5% wt. NaCl, NaNO3, NaF or Na2SO4. Purified synthetic cryolite is recovered.