Chromium(III) hydroxide formation, 2 of 3. When 0.125M chromium(III) potassium sulfate (KCr(SO4)2) is poured into a beaker with 0.5M sodium hydroxide (NaOH), green chromium(III) hydroxide (Cr(OH)3) is formed. The reaction is KCr(SO4)2 + NaOH -> Cr(OH)3 + KNaSO4 + Na2SO4.