A process for the purification of the sodium formaldehyde sulfoxylate

摘要

A process for the purification of the sodium formaldehyde sulfoxylate, the the preparation of an aqueous solution of sodium formaldehyde sulfoxylate of zinc, sulfurous acid and formaldehyde, the addition of a stoichiometric excess of sodium sulfide to the aqueous solution for the separation of the heavy metals, the detection of sodium sulfide, which remains in solution, according to a colorimetric method or according to a method using an ion electrode and the addition of a metal halide, which is made of zinc chloride, copper chloride or nickel chloride is selected, in an equivalent amount relative to the thus detected sodium sulfide to the solution for the separation of the sulfide comprises as a metal sulphide.