Of other lead minerals we may mention the basic sulphate lanarkite, PbO PbSO 4; leadhillite, PbSO 4.3PbCO 3; the basic chlorides matlockite, PbO PbC12j and mendipite, PbC1 2.2PbO; the chloro-phosphate pyromorphite, PbC12.3Pb3(P04)2, the chloro-arsenate mimetesite, PbC12.3Pb3(As04)2; the molybdate wulfenite, PbMoO 4; the chromate crocoite or crocoisite, PbCrO 4; the tungstate stolzite, PbW04.
When kept fused in the presence of air lead readily takes up oxygen, with the formation at first of a dark-coloured scum, and then of monoxide PbO, the rate of oxidation increasing with the temperature.
Pb 2 0, PbO, Pb0 2, Pb203 and Pb304.
The monoxide, PbO, occurs in nature as the mineral lead ochre.
Another oxychloride, PbC1 2.7PbO, known as "Cassel yellow," was prepared by Vauquelin by fusing pure oxide, PbO, with one-tenth of its weight of sal ammoniac. "Turner's yellow" or "patent yellow" is another artificially prepared oxychloride, used as a pigment.
Zeit., 1889, 13, p. 1701; 17, p. 1712) adds calcium plumbate to a solution of potassium ferrocyanide and passes carbon dioxide through the mixture: 2K 4 Fe(NC) -f-Ca 2 PbO 4 -} 4C02= K3Fe(NC)6+ K2C03+PbC03+2CaC03.
A simpler explanation is that the manganese dioxide first gives a normal sulphite which rearranges to dithionate, thus: Mn0 2 +2S0 2 = Mn(S03)2-MnS206, whilst the lead dioxide gives a basic sulphite which rearranges to sulphate, thus: PbO-l-S0 2 = PbOS03 - > PbS04.
When digested for some time with a caustic alkali it is converted into a basic salt, PbCrO 4 PbO, a pigment known as "chrome red."