206 On Tungsten. [Szpr. 
thick. This crucible was enclosed in a larger one, and both were 
covered by a third crucible. In this state they were exposed for an 
hour and a half to the strongest heat of a blast furnace. The result 
appeared to me very surprising, The whole contents of the crucible, 
with a portion of the vessel itself, were melted into a slag. ; 
This surprising result, the cause of which requires to be cleared up 
by further experiments, was probably owing to a portion of the triple 
compound of oxide of tungsten, potash, and muriatic acid, which 
not having been exposed to a red heat, was soluble in ammonia, and 
therefore was present in our tungstate ‘of ammonia. _ This was not 
the case in the first experiments, because the salt had been prepared 
from an oxide exposed to a red heat, and was therefore free from 
this triple compound. Hence the pure oxide was reduced, and 
gave us the good results which have been above described. 
Exper. 18.—200 gr. of the same tungstate of ammonia were 
kept in a weak red heat in a long small glass vessel placed in a cru- 
cible, till the ammonia was completely dissipated. The mass, when 
cold, weighed 134 gr., and had the following properties. Its colour 
was light greenish yellow, and was in the state of a scaly powder, 
which dissolved readily in caustic potash with the assistance of heat, 
without the evolution of any ammonia. The 129 gr. of this powder 
that remained were exposed for an hour to a strong red heat, which 
melted the glass in which the oxide was contained. Its weight was 
reduced to 121 gr., and it exhibited the following properties. The 
uppermost layer had a dark greyish blue colour, which always be- 
came more and more grey as we came nearer the bottom, and ap- 
peared to crystallize finely in stars. At the bottom of the glass itself 
there was a hard whitish grey mass, which from its weight I was dis- 
posed to consider as tungsten reduced to the metallic state. To 
obtain satisfactory information respecting this point, I mean the 
possibility of reducing tungsten without the assistance of charcoal, 
or any body containing hydrogen; the 12] gr. were reduced toa 
fine powder, and crammed into a crucible lined with charcoal, 
covered with charcoal powder, and exposed, as in the preceding 
experiments, for an hour to the most violent heat that could be 
raised in a blast furnace. The result was as follows. ‘The oxide had 
partly sunk through the crucible, and was partly melted into a 
porous grey substance, with not the least appearance of a regulus. 
These results leave us to conjecture how they happened. They 
were beyond all doubt owing to the presence of a portion of the 
triple compound of oxide of tungsten, potash, and muriatic acid, 
as was the case in the preceding experiments. 
The existence of a portion of this triple compound in our tung- 
state of ammonia, and the injurious effects which it produced when 
we attempted to reduce the metal, induced me to undertake a set 
of experiments in order to obtain pure tungstate of ammonia from 
the oxide of tungsten not exposed to a red heat, and obtained as in 
experiment 10, 
