METHOD FOR PURIFICATION OF BISMUTH BY ZONE MELTING, COVERING FLUX AND APPARATUS FOR IMPLEMENTATION OF ZONE MELTING METHOD Russian patent published in 2020 - IPC C22B9/02 C22B30/06 

FIELD: chemistry.

SUBSTANCE: group of inventions relates to coating fluxes for coating a surface of a melted crystallization zone for purification of bismuth by zone melting, a method for purification of bismuth by zone melting and a device for zone melting for purification of bismuth. Method for purification of bismuth by zone melting includes operations of melting and crystallisation of separate sections of longitudinal ingot. In order to increase product output and accumulate impurities in one section separated from cleaned section, crystallisation process is carried out under layer of coating flux, which is more low-melting than bismuth, with consumption providing coating of molten zone of ingot with layer of 0.5–2 mm. Covering flux for coating surface of melted crystallization zone for purification of bismuth by zone melting contains components which form low-melting eutectic, additionally contains salt-oxidizer in following ratio, wt. %: sodium sulphite - 3; sodium hydroxide - 22–24, potassium hydroxide or in following ratio: sodium nitrate - 3, potassium hydroxide is the rest.

EFFECT: technical result consists in concentration of impurities in one sector with simplification of their unloading separately from weight of purified bismuth.

4 cl, 2 dwg, 1 tbl