1815.} On, Tungsten. 205 
as that employed in the preceding experiments, were, as in experi- 
ment 14, exposed to a strong red heat for an hour in a glass sur- 
rounded with charcoal in acrucible. The result differed little from 
that obtained in the 14th experiment. The mass which remained 
behind after the process weighed 100 gy., and had the following 
_ properties. When spread upon a leaf of paper, that portion of it 
which had been in contact with the charcoal appeared grey or me- 
tallic. In the middle it was dark brownish red, passing into reddish 
brown, and almost the fourth part of the mass was of a fine violet 
colour below, owing probably to a mixture of dark blue and brownish 
red oxide. 
88 gr. of this mass, or as much as the portion of brown oxide 
amounted to, were, as in the 14th experiment, rammed into a 
small Hessian crucible, and ‘exposed to the strongest heat of a blast 
furnace for an hour anda half. ‘The result of this operation was as 
follows. The oxide of tungsten was completely reduced, but was 
not in the state of a button, or in large grains, but in small grains, 
as fine as sand, having a strong metallic lustre, a light iron-grey 
colour, and slightly agglutinated. The weight amounted to 75 gr. 
A few pieces of a larger size were to be found among this sand; 
they consisted of the portions that had adhered to the sides and 
bottom of the crucible. 
The metal obtained by this process possessed the following pro- 
perties. When strongly rubbed upon a hard and smooth body, it 
assumed a strong metallic lustre, and appeared very hard and brittle. 
212 gr. of this substance, composed of grains more or less aggluti- 
nated together, and of the size of pin heads, were weighed in the 
usual way in distilled water, and the specific gravity was found to 
be 17:400. ‘This result is intermediate between the specific gra- 
vity of tungsten as stated by the Elhuyarts, namely, 17°600; and 
by Allen and Aiken, namely, 17:200. It leaves no doubt respecting 
the great specific gravity of this metal. 
Partly to ascertain these facts with still greater accuracy, and 
partly to obtain a greater quantity of tungsten in the metallic state 
for further experiments, and lastly to put the properties of tungstate 
of ammonia in the fire, and the nature of the oxide which it leaves 
beyond doubt, the following experiments were made. 
Exper. \7.—200 gr. of tungstate of ammonia, which had been 
obtained from oxide of tungsten not heated to redness in the 
manner described in experiment 10, were put into a small glass, 
which was put into a crucible, and exposed to a strong red heat for 
half an hour. The oxide was not covered with any charcoal 
wder. By this process the upper portion of the glass was melted. 
The oxide obtained had a dark greyish blue colour, almost slate- 
blue, and had in some measure assumed a crystalline appearance. 
It weighed 173 gr. 
These 173 gr. were crammed into a crucible lined with charcoal 
powder, and covered with a layer of charcoal powder one finger 
