Cryolite prepn. from fluorine contained in waste gas - from electrolytic plant for mfg. aluminium etc. by pptn. with sodium aluminate and alkali halide

摘要

Pptn. of cryolite from a dil. aq. soln. of HF, obtd. by wet scrubbing gas leaving fused electrolyte tanks for mfr. of aluminium is claimed. The dil. soln. is modified by addn. of >=1 alkali halide and sufficient sodium aluminate to transform the HF into cryolite. The alkali halide is pref. NaCl added in amt. 10-200 g/l. Increased yield of cryolite is obtd. since the addn. of the alkali halide markedly lowers the solubility of the cryolite.