320 Mr . Hatchett’s Analysis. 
shall soon have occasion to prove, that the real quantity of 
sulphur is much more considerable in the latter than in the 
former. 
As soon as muriatic acid is poured on the powder of the 
magnetical pyrites, a slight effervescence is produced, which 
becomes violently increased by the application of heat ; a quantity 
of gas is discharged, which, by its odour, bv its inflammability, 
by the colour of the flame, by the deposition of sulphur when 
burned, and by other properties, was proved to be sulphuretted 
hydrogen. 
During the digestion, sulphur was deposited, which so enve- 
loped a small part of the pyrites, as to protect it from the tarther. 
action of the acid. 
The solution was of a pale yellowish-green colour. With 
prussiate of potash it afforded a pale blue precipitate, or rather a 
white precipitate mixed with blue ; and with ammonia it formed 
a dark blackish-green precipitate, which gradually became ochra- 
ceous; so that these effects corroborated the conclusions which 
were founded on the properties of the sulphuric solution, namely, 
that the iron contained in the pyrites, is almost, if not quite, in 
the metallic state. 
Other experiments were made ; but, as they merely confirm 
the above observations, I shall proceed to give an account of the 
analysis. 
§ IV. 
ANALYSIS OF THE MAGNETICAL PYRITES. 
A. One hundred grains, reduced to a fine powder, were 
digested with two ounces of muriatic acid, in a glass matrass 
placed in a sand bath. The effects already described took 
