In the arts, tungsten bronzes of different colours are used, namely, golden-yellow, reddish-yellow, purple-red, and blue. The first two crystallize in forms resembling cubes, while the third is obtained partially in cubes and partially in amorphous pieces, and the last-named forms prismatic crystals. Other circumstances being equal, the yellow bronze is obtained from mixtures poor in acid, the other two from those containing more acid. But the colour is dependent not merely on the composition of the soda tungstate salt, but also on the amount of tin, and on the duration of the fusion; so that when much tin is used, and the fusion is prolonged, a yellow bronze is obtained from a very acid mixture, and, on the contrary, a salt that is but slightly acid, when fused only a short time and with very little tin, may yield a red or even a blue bronze.

A mixture of two molecules of soda tungstate and 1 of anhydrous tungstic acid, with tinfoil slowly added, and kept melted for 1 or 2 hours?, will yield cubes 1/3 in. long when about 4 oz. are melted, and they will produce a yellow or reddish-yellow bronze, the powder of which seems light brown, and when stirred up with water it imparts to the liquid the property of appearing of a fine blue colour by transmitted light.

The red bronze obtained from 10 parts soda carbonate, 70 soda tungstate, and 20 tinfoil yields, on pulverization, a powder that, stirred up in water, transmits green light.

According to J. Philipp, a blue bronze is always obtained if the fused mixture contains more than 3 molecules of tung-stic acid to 1 of soda; if the fused product is boiled alternately with muriatic acid and with carbonate of soda, the result will be a considerable quantity of fine blue prismatic crystals, with which there are intermixed, in most cases, single red and yellow cubes.

Moreover, all the tungsten bronzes obtained by fusion with tin can also be prepared by electrolysis of fused acid tungstates, but the yield is so small that it is unprofitable. {Ind. Zeif)