1815.j On Tungsten. < 207 
(C.) 
Experiments on the best Method of obtaining pure Tungstaie of 
© Ammonia from ihe Oxide of Tungsten procured from the triple 
Compound, in the way described in Eaperiment 10, and not ex- 
posed to a Red Heat. 
Exper. 19.—250 gr. of yellow oxide of tungsten that had not 
been heated to redness were mixed with 1 oz. of caustic ammonia 
and 1 oz. of water, and the mixture was left for 12 hours in a mo- 
derately ‘warm place. ‘The whole was then thrown upon a moist 
filter, and the filtered liquid, being put into a porcelain dish, was 
placed upon a stove, that it might undergo slow evaporation. After 
about the half of the liquid had evaporated, snow-white brilliant 
prisms began to separate, and they continued to accumulate till the 
whole liquid was reduced to half an ounce. These crystals, being 
separated, were found to weigh 133 gr. They had not the properties 
of pure tungstate of ammonia, which is known to be very soluble : 
on the contrary, these were very difficultly soluble ; and from their 
appearance, could-be nothing else than a quadruple compound of 
oxide of tungsten, potash, ammonia, and muriatic acid. The exist- 
ence of these substances in these crystals was ascertained by further 
experiments made with a view to ascertain their nature. Thus a 
portion, being exposed to a red heat, left after the escape of the 
ammonia a blue, greenish white residuum, which when boiled in 
-muriatic acid became yellowish, like the triple salt ef which we 
-have spoken so frequently. In another experiment the quadruple 
compound was dissolved in caustic potash, with the escape of a 
great deal of ammonia. The potash being neutralized by acetic 
acid, the white triple compound precipitated, which remained. un- 
altered in a gentle red heat; but being boiled in concentrated mu- 
riatic acid, acquired a yellow colour. 
The white residuum of the oxide treated, as above, with ammonia 
and water, was once more digested in 1 oz. of caustic ammonia and 
1 oz. of water, and the filtered liquid exposed, as before, to: slow 
evaporation upon a stove. When the half was evaporated, crystals 
appeared, as before. The whole of them obtained amounted to 
43 gr. They possessed the same properties as those just described. 
The mother leys from which these crystals had deposited were 
evaporated separately. The first yielded 45 gr. of a saline mass, for 
the most part very soluble in water, and which possessed the pro- 
perties of tungstate of ammonia, containing, however, mixed with 
‘at, a small portion of the quadruple compound. 
The second yielded 37 gr. of a saline mass, possessing the pro- 
perties of the preceding. 
These 82 gr. were macerated in 3 dr. of distilled water, and the 
undissolved white quadruple compound, which weighed 33 gr., was 
separated from the easily soluble portion. The solution was slowly 
evaporated in a porcelain dish, There remained 48 gr. of a salt, 
