120 ON OFFICINAL SULPHUR PR^CIPITATUM . 
ART. XXXII.— ON OFFICINAL SULPHUR PR^CIPITATUM 
By Dr. Otto, of Brunswick. 
The officinal precipitated sulphur varies much in exter- 
nal appearance ; sometimes it is of a pure yellowish-white, 
sometimes of a more or less dirty grayish or even brownish- 
white. It could not be accounted for why the former 
colour was peculiar to the preparation obtained from the 
sulphuret of calcium, and the latter to that prepared from 
the ordinary sulphuret of potassium. From some experi- 
ments which have been made in my laboratory, it has re- 
sulted that the dirty-coloured appearance of the latter pre- 
paration is owing to certain impurities, especially to an 
amount of sulphuret of copper. Ordinary potash (always 
or nearly so) contains copper ; this passes into the purified 
potash, and from this into the sulphuret of potassium, which, 
on saturation with acids, deposits sulphuret of copper. Car- 
bonate of potash prepared from tartar yields a yellowish 
white sulphur pr&cipitatum, like the sulphu ret of calcium. 
A preparation thrown down from ordinary sulphuret of 
potassium retains its dirty colour even when fused with pure 
carbonate of potash, and again precipitated with acids, but 
the dirty colour disappears immediately on pouring chlorine 
water on it (in the dry state, for when recently precipitated 
it is converted by it entirely into sulphuric acid,) and the 
copper may be detected without difficulty in the solution, 
and likewise in the residue left on incineration. If some 
pure carbonate of potash, prepared from tartar, be fused 
with surphur, with the addition of some oxide of copper, 
a sulphuret may be obtained, from which acids throw down 
a more or less brownish-white precipitate. Sulphuret of 
iron likewise appears to occur constantly in the prepara- 
tion obtained from ordinary sulphuret of potassium. It 
appears therefore absolutely requisite that in future the sul- 
phur prsecipitatum be prepared solely from the sulphuret of 
calcium. — Ibid, from Pharmaceut. Central Blatt. 
