Wolfram (tungstate of iron and manganese) occurs in some of the states, notably in New South Wales, Victoria, Tasmania and Queensland.
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.
Of the impurities of the ore the wolframite (tungstate of iron and manganese) is the most troublesome, because on account of its high specific gravity it cannot be washed away as gangue.
His next discovery, in 1781, was the composition of the mineral tungsten, since called scheelite (calcium tungstate), from which he obtained tungstic acid.
TUNGSTEN [[[symbol]] W, atomic weight 184 o (0=16)], a metallic chemical element found in the minerals wolfram, an iron and manganese tungstate, scheelite, a calcium tungstate, stolzite, a lead tungstate, and in some rarer minerals.
It dissolves in potash, giving potassium tungstate and hydrogen, and is readily oxidized to the trioxide.
A crystalline form was obtained by Debray as olive-green prisms by igniting a mixture of sodium tungstate and carbonate in a current of hydrochloric acid gas, and by Nordenskjold by heating hydrated tungstic acid with borax.
Tungstic acid, H 2 W0 4, is obtained as H 2 W0 4 H 2 0 by precipitating a tungstate with cold acid; this substance has a bitter taste and its aqueous solution reddens litmus.
Graham obtained a colloidal tungstic acid by dialysing a dilute solution of sodium tungstate and its equivalent of hydrochloric acid; on concentrating in a vacuum a gummy product is obtained, which still remains soluble after heating to 200°, but it is converted into the trioxide on heating to redness.
The most important tungstate is the so-called tungstate of soda, which is sodium paratungstate, NaloW12041.28H20.
The sodium compound was first obtained by Wohler on reducing sodium tungstate with hydrogen; coal-gas, zinc, iron or tin also effect the reduction.
A blue bronze, Na2W5015, forming dark blue cubes with a red reflex, is obtained by electrolysing fused sodium paratungstate; a purple-red variety, Na2W309, and a reddish yellow form result when sodium carbonate and sodium tungstate are heated respectively with tungsten trioxide and tinfoil.
2KF WO 2 F 2 H 2 O, is obtained as crystalline scales by dissolving normal potassium tungstate in hydrofluoric acid and adding potassium hydroxide till a permanent precipitate is just formed.
The trisulphide, WS3, is obtained by dissolving the trioxide in ammonium sulphide or by passing sulphuretted hydrogen into a solution of a tungstate and precipitating by an acid in both cases.