6Fe(NH4)2(SO4)2 + 7H2SO4 + K2Cr2O7 → 3Fe2(SO4)3 + Cr2(SO4)3 + 6(NH4)2SO4 + K2SO4 + 7H2O
Diammonium-iron(II) sulfate react with sulfuric acid and potassium to dichromate produce iron(III) sulfate, chromium(III) sulfate, ammonium sulfate, potassium sulfate and water. Sulfuric acid - diluted solution.