294 M. Bernoulli on Tungsten and its Alloys. 
made. With copper, reguli were obtained, which, however, were 
not homogeneous; the individual particles could be distinctly 
seen. In general it was also found that copper, lead, zine, 
antimony, bismuth, cobalt, and nickel only became alloyed with 
tungsten when the reduction of the two metals took place simul- 
taneously. The alloys are so infusible, that, with more than 10 
per cent. of tungsten, no reguli are obtained, and at a higher 
temperature the more volatile metals escape and metallic tungsten 
is left behind. Iron differs in this respect from other metals. 
It alloys in all proportions with tungsten; with above 80 per 
cent., however, the alloys are infusible. 
In order to prepare the tungstic acid used in these experi- 
ments, powdered Wolfram was fused with excess of carbonate of 
soda in an iron crucible, the fused mass dissolved, and boiled to 
reduce manganic acid, and filtered. The solution, which con- 
sisted of tungstate and carbonate of soda, was neutralized with 
nitric acid, and the tungstate of soda crystallized out. This was 
dissolved and treated with nitric acid, and the precipitate of hy- 
drated tungstic acid was well washed. It was then dissolved in 
ammonia, which left a residue of niobic and silicic acids; the 
evaporated liquor deposited a fine crop of crystals of tungstate of 
ammonia. This was well washed with water, and then repeatedly 
treated with fresh quantities of nitric acid for some days to 
remove nitrate of ammonia. The acid was ultimately washed 
out and gently heated, by which it was obtained of a fine pure 
sulphur-yellow colour. 
The author found, in all these experiments, that it was not 
possible to obtain pure yellow acid by directly heating the tung- 
state of ammonia, even when this was done under access of air. 
It invariably became of a green colour. This has been observed 
before, and has been differently interpreted, some ascribing it to 
the formation of a suboxide, and some to an admixture of yellow 
acid and the blue oxide W? O°. 
Bernoulli has found that it is a true compound. When the 
yellow acid was heated to the highest temperature of a gas blow- 
pipe, it gradually changed to a green colour, and from being 
amorphous became crystalline. Similar results were obtained 
by using the high temperature of a stoneware furnace, which 
has an oxidizing flame. The tungstic acid was placed in suit- 
ably protected platinum crucibles, and heated for periods varying 
from eighteen to seventy-two hours. A green crystalline mass 
was obtained, while on the upper part of the crucible there were 
smaller crystals of the same colour. When the caked mass was 
divided and subjected to a further heat for eighteen hours, the 
result was confirmed; part had sublimed in fine crystalline lamin. 
Bernoulli analysed these two modifications by reduction with 
