40 G. E. Moore—Amorphous Mercurie Sulphide. 
The most convincing proof of the correctness of this supposi- — 
tion was afforded by the direct conversion of the mineral into 
the red modification. A small portion was triturated with 
water to the finest powder, sealed in a tube with solution of 
ernie pentasulphide, and exposed to the temperature of — 
iling water. The powder, which was pure black at first, — 
showed on the morning of the third day a decided tinge of red. 
As soon as no further change could be perceived, the tube was — 
opened. - The powder then showed a brownish red color, not of — 
course to be compared with vermilion, but still quite satisfac — 
tory to one familiar with the refinements of manipulation re | 
quired to produce the finer shades of color in the latter sub- 
stance, and, perhaps, all that could be expected, in view of the 
great difference in susceptibility to chemical action usually 
existing between a native mineral and an artificial precipitate. — 
It was still desirable to compare the specific gravity of the 
mineral with that of the black precipitated mercuric sulphide. — 
As, however, I have been unable to find any recorded deter- 
mination of the latter, it was necessary to determine it myself — 
This was at first no easy matter. The precipitate possesses 10 
an eminent degree the annoying peculiarity of retaining, with 
great tenacity, a coating of air, which makes a perfect admix- 
ture with water well nigh unattainable by ordinary means — 
When boiled, the mixture spirts with almost explosive violence, — 
and forms in addition a greasy-looking scum, which cannot be — 
made to sink. Attempts to use the air-pump in the ordinary — 
manner were likewise unsuccessful, on account of the strong — 
foaming which ensued. I was, therefore, obliged to have — 
recourse to an expedient of which, as it may perhaps be useful — 
to others in similar difficulties, a detailed description may not — 
appear superfluous. 
ure mercuric sulphide was prepared by the action of sul- 
phureted hydrogen on solution of mercuric nitrate. Every 
care was taken to insure perfect saturation, and, after thor- 
ough washing and drying, the mass was repeatedly digested 
with pure carbon disulphide, until all free sulphur had been 
removed. 
After careful drying, a weighed portion was placed in @ 
weighed specific gravity flask of the ordinary pattern. This — 
was connected with a Bunsen’s pump,* by means of a triply 
bent tube, fig. 2, whose middle part had been widened out into — 
a bulb of about equal capacity with the flask itself, the com- 
munications between the bulb-tube, which was filled to three 
fourths with water, and the flask being made air-tight by means” 
* As Bunsen’s pump is not alwavs to be found so perfect in construction as t0 
permit the attainment of the maximum degree of rarification, it may be pre: 
ee ee et ee I ee ae eee 
f th 
ble in most cases to use Sprengel’s mercury air-pump. 
