Na2[Sn(OH)6] + 4Na2S Na4[SnS4] + 6NaOH
Sodium hexahydroxostannate(IV) react with sodium sulfide to produce sodium trithiostannate(IV) and sodium hydroxide. Sodium hexahydroxostannate(IV) and sodium sulfide - concentrated solutions. This reaction takes place at a temperature of 90-100°C.