Lead Orthophosphate, Pb₃(PO₄)₂

The normal salt is precipitated by adding a dilute acetic acid solution of lead acetate to excess of a boiling solution of sodium hydrogen phosphate. If the precipitation takes place in the cold PbHPO₄ is formed, but is changed into the normal phosphate by lengthened boiling with water; the latter salt is also slowly hydrolysed by boiling water. Lead phosphate is a yellow, amorphous powder, whose solubility in water amounts to 1.66×10^-7 molecule per litre. It dissolves in caustic alkali solution.