Basic Lead Sulphates

By an investigation of the cooling curves of various fused mixtures of lead sulphate and monoxide Schenck and Rassbach have found evidence of the existence of three basic lead sulphates, viz. PbSO₄.PbO, PbSO₄.2PbO, PbSO₄.3PbO, the first of which is the best defined.

PbSO₄.PbO or Pb₂OSO₄ is formed by the action of ammonia on lead sulphate, and by shaking together lead sulphate and lead hydroxide with water at 18° C. It is obtained as a white, voluminous powder, and occurs as the mineral lanarkite. PbSO₄.3PbO.H₂O or Pb₄O₂(OH)₂SO₄ is formed by the interaction of lead hydroxide and ammonium sulphate solution, or by shaking lead sulphate and lead hydroxide with water.

According to Pleissner 1 litre of saturated solution at 18° C. contains 13.4 mg. of PbSO₄.PbO and 26.2 mg. of PbSO₄.3PbO.H₂O.

A basic lead sulphate known to the trade under the name of Purex is made by volatilising galena in a current of air. The product constitutes a useful white pigment, much less poisonous than ordinary white lead.