Chromium(III) hydroxide formation, 1 of 3. When 0.125M chromium(III) potassium sulfate (KCr(SO4)2) is poured into a beaker with 0.5M sodium carbonate (Na2CO3), green chromium(III) hydroxide (Cr(OH)3) is formed. The reaction is Cr3+ + [CO3]2- -> Cr(OH)3 + H2O + CO2.