208 Progress of Foreign Science. 
Ill. Inorcanic CHEMISTRY. 
i. On the Chemical Composition of the white efflorescing Pyrites, 
by M. Berzelius*. 
It is known that the crystalline form of the white pyrites dif- 
fers so essentially from that of the yellow pyrites, that M. Haiiy 
thought he ought to separate them, as two different mineral 
species. Yet chemical analysis finds no difference of com- 
position between these two substances, which appear to add 
one example more to the exceptions to the general rule, which 
are furnished by the differences between the two forms of car- 
bonate of lime, and that more lately observed by M. Mitscher- 
lich, in the two forms of the super-phosphate of soda. 
White pyrites presents two varieties, one of which perfectly 
crystallized does not change in the air; while the other, which 
exhibits a confused crystallization, effloresces on exposure to 
air, and falls into a powder evidently vitriolic. This phe- 
nomenon, therefore, proves a difference of composition between 
these two varieties ; a difference deserving of being studied, in 
order to learn if it be such, as might explain to us their differ- 
ences from yellow pyrites. 
_ M. Berzelius left a piece of white pyrites to effloresce for two 
years and a half; and when it was entirely disintegrated, he 
undertook its examination. Its volume was nearly doubled; 
it was split in every direction, and fell into fragments on the 
slightest touch. A part of its mass was converted into a white 
powder, of a styptic taste, and this powder was beginning to 
turn yellow on the extreme points. Viewed under a micro- 
scope, it presented a mass full of small clefts, filled with a 
white efflorescing salt, the interstices of which appeared to be 
white pyrites, untouched and more or less crystalline. 
He treated a certain portion of it with water; separating 
the solution from the insoluble residuum. The latter consisted 
partly of a coarse powder, which was composed of small grains 
of pyrites, and partly of a powder, which was finer, lighter, 
and of a grayish or almost black colour. When viewed under 
the microscope, this powder presented merely brilliant particles 
of pyrites, without any trace of sulphur evolved and mingled 
with the pyrites. 
(a) The solution deposited, on contact of air, a yellow ochre ; 
it was therefore entirely neutral. He treated this solution, 
with nitric acid, to oxidize the iron to a maximum, and he then 
decomposed it by means of muriate of barytes and caustic 
ammonia. It yielded 2.03 grains of sulphate of barytes; and 
after the separation of the excess of the muriate of barytes by 
sulphuric acid, 0.68 grains of peroxide of iron. The weights are 
* Annales de Chim. et de Phys,, May, 1822. 
