Berzelius on the Sulphurets. 209 
precisely those which the neutral sulphate of the protoxide of 
iron ought to have given (Fe S2); for 
29.16 : 9.78 3; 2.03 : 6.809. 
The salt formed was equivalent to 0.74 grains of proto-sulphu- 
ret of iron (Fe S*) ; but the undecomposed residuum of pyrites 
weighed 4.653 grains, that is to say, 6 and 7 times as much as 
the effloresced portion *. 
(2) To satisfy himself that the insoluble residuum contained 
no free sulphur, he dissolveda portion of the most finely divided 
part in nitro-muriatic acid, till the sulphur was entirely acidified. 
There remained a little undissolved silica, The solution 
afforded 0.64 grains of oxide of iron, and 3.82 grains of sul- 
phate of barytes, which is in perfect accordance with the com- 
position of deuto-sulphuret of iron; that is, with pyrites. Now 
since the effloresced portion was a sulphate with a base of pro- 
toxide, containing no acid in excess, and since there were no 
traces of sulphur separated during the efflorescence, it is evi- 
dent that the effloresced portion was a proto-sulphuret of iron 
(Fe S*), which has not been hitherto found in an insulated 
state in the mineral kingdom+; and that the remainder which 
was not subject to effloresce, was a deuto-sulphuret (Fe S*), 
The efflorescing pyrites can be, therefore, nothing else but 
particles more or less completely crystallized of Fe S4, ce- 
mented together by particles much less numerous of Fe S2, 
which are converted by degrees, at the expense of the air and 
its humidity, into Fe S2: pyrites loses thus its coherence, in 
proportion as the crystallized particles are destroyed. The 
efflorescence contributes in no respect, therefore, to the solution 
of the question of the diversity of the forms of yellow and 
white pyrites. 
On the Composition of the Alkaline Sulphurets. By M. Berzelius. 
The first question to be resolved is, if the sulphur can com- 
bine directly with an oxidized body; or, if there be then formed 
a sulphate and a metallic sulphuret, as M. Vauquelin has 
presumed. 
1. Experiments to determine if the Hepar formed in the dry way 
is a sulphuret of an oxide, or of a metal. 
1. It is clear, that if a sulphuret of potash can exist, it ought 
to be formed, for example, when we reduce sulphate of potash, 
and that after the solution in water of the compound reduced, 
the result ought to be entirely different, if it is sulphuret of 
potash, or of potassium. To verify this fact, he made use of a 
_* Cesta dire six et sept fois autant que la partie effleurie.—Annales, 
xix. p. 449, 
_ t Magnetic pyrites, which does not effloresce, is a chemical combina- 
tion of Fe S* + 6 Fe S82, 
