Lead Dihydrogen Phosphate, Pb(H2PO4)2, is obtained by dissolving PbHPO4 in hot 90 per cent, phosphoric acid, and crystallising the solution. It forms fine needles which are hydrolysed by water (Alders and Stahler).
The basic salt Pb3(PO4)2.PbO is formed by heating the double salt Pb3(PO4)2.Pb(NO3)2.2H2O.
The salt 3Pb3(PO4)2.PbCl2 occurs naturally as pyromorphite and can be prepared artificially by heating its constituent salts together. It forms yellow, hexagonal crystals of density 7.008. The hydrate 3Pb3(PO4)2.PbCl2.H2O has also been prepared, as well as the salts 3Pb3(PO4)2.PbBr2 and Pb3(PO4)2.PbI2.
The crystalline compound 2Pb(HPO4)2.Pb(NO3)2 is formed by the evaporation of a solution of Pb3(PO4)2 in nitric acid; and Pb3(PO4)2.Pb(NO3)2.2H2O is precipitated when an insufficiency of sodium phosphate is added to lead nitrate solution. The latter may be crystallised from nitric acid and yields the basic salt Pb3(PO4)2.PbO on ignition. |