Ca + O2 -> CaOCaO + H2O -> Ca(OH)2Ca(OH)2 + CO2 -> CaCO3
As + O2 -> As2O5As2O5 + 3H2O -> 2H3AsO4H3AsO4 + 3NaOH -> Na3AsO4 + 3H2O
Ca + O2 -> CaO
CaO + H2O -> Ca(OH)2
Ca(OH)2 + CO2 -> CaCO3
As + O2 -> As2O5
As2O5 + 3H2O -> 2H3AsO4
H3AsO4 + 3NaOH -> Na3AsO4 + 3H2O