One of the ways to extract tin from tinplate waste is to dissolve tin in alkaline solutions containing methanitrobenzoic acid, followed by electrolysis. The technological solution is a complex multicomponent system. In addition to free alkali and methanitrobenzoic acid, it may contain stannates and stannites of tin, as well as various nitrobenzoic acid reduction products (azoxy-, azo-, hydrazo- and other compounds). The formation of carbonates is inevitable due to the absorption of carbon dioxide from the air ...