3Sn(OH)2 + 2K2CrO4 + 8KOH + 8H2O → 3K2[Sn(OH)6] + 2K3[Cr(OH)6]
Tin(II) hydroxide react with potassium chromate, potassium hydroxide and water to produce potassium hexahydroxostannate(IV) and potassium hexahydroxochromate(III). Potassium hydroxide - concentrated solution.