The molybdate solution should be of such a strength that i cc. will precipitate o oi gramme of lead.
Molybdenum trisulphide, MoS3, is obtained by saturating a solution of an alkaline molybdate with sulphuretted hydrogen and adding a mineral acid.
As long as the solution contains lead, the addition of the molybdate solution causes a precipitation of white lead molybdate.
Chem., 18 94, 5, p. 280), by heating pure sodium molybdate in hydrochloric acid and estimating the amount of sodium chloride formed, obtained the value 96.087.
A standardized solution of ammonium molybdate is then added from a burette.
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.
Ann., 1826, 8, p. 23), by converting lead molybdate into lead nitrate, obtained the value 95.
There are several volumetric methods for assaying lead ores, but the best known is that based on the precipitation of lead by ammonium molybdate in an acetic acid solution.