3Fe2(SO4)3 + 4Na3AsO4 + 16H2O → 2{Fe3(OH)3(AsO4)2•5H2O} + 6Na2SO4 + 3H2SO4
Iron(III) sulfate react with sodium orthoarsenate and water to produce pentahydrate triiron(III) trihydroxide-diorthoarsenate, sodium sulfate and sulfuric acid. Sodium orthoarsenate - diluted solution.