in water byproducts: NaH2PO4; as by-product: on synthesis of NaH2PO4 from Na3PO4 and Na2HPO4 with SO2, pptn. of NaH2PO4, formation of NaHSO3, oxidation of NaHSO3 in presence of H2O and S at 150-180°C under pressure;;
in water pptn. of Na2SO4 on addn. of MgSO4 to NaCl-soln. (waste-liquors), generation of HCl from by-product MgCl2, introduction of HCl into the hot Na2SO4-soln. (pptn. of NaCl);;
