igo Mr. Howard's Experiments and Observations 
examined the pyrites. Their very loose texture made it ex- 
ceedingly difficult to collect the weight of 16 grains, which was 
however effected by the dexterity of the Count de Bournon, 
I digested these, at a low heat, with weak muriatic acid; 
which acted gradually, and disengaged a trifling but sensible 
quantity of sulphureted hydrogen gas. After several hours, I 
found the acid discontinued its action. The whole metalline part 
appeared in solution ; but sulphur and earthy particles were 
observable. The sulphur, from its small specific gravity, was 
suspended through the solution ; whilst the earthy matter, which 
could not be separated by mechanical means, was fortunately 
left at the bottom of the digesting vessel. I decanted off the 
solution, holding suspended the sulphur; and, by repeated 
washing, separated every thing belonging to the pyrites from 
the insoluble earthy matter, the subtraction of which reduced the 
weight of real pyrites to 14 grains. I next obtained the sulphur, 
by filtration. When it was as dry as I could make it, without 
fear of its being sublimed, its weight was two grains. To the 
filtrated liquor I added nitrate of barytes, by way of detecting 
any sulphuric acid which might have been present; but no 
cloudiness ensued. I then separated, by sulphate of ammonia, 
the barytes thus added, and precipitated the iron with ammonia. 
The liquor, on the subsidence of oxide of iron, appeared of a 
violet purple colour : it contained nickel, which I threw down 
with sulphureted hydrogen gas, there being already a sufficient 
excess of ammonia in the saline liquor to form an alkaline 
hydrogenized sulphuret. The oxide of iron, after ignition, 
weighed 15 grains; and the sulphuret of nickel, reduced to an 
oxide, weighed, after the same treatment, something more than 
one grain. The proportions of the substances contained in the 
