418 Neientific Intelligence. 
tains the soda salt of a nitrogenous but non-sulphurous acid, which is 
nothing else than Gmelin’s cholic acid, and may be obtained in a crys- 
talline form. It is most readily prepared from erystallized gall, by pre- 
cipitation with sulphuric acid and addition of ether, whereupon it crys- 
tallizes in fine needles. 
Its formula is, C,, H,, NO, ,-@HO. 
Besides this acid, ‘there i is also a body containing sulphur in the gall, 
n 
tion almost invariably escapes decomposition. ‘To obtain the mineral 
in a state of minute division, Fresenius recommends elutriation, and di- ° 
rects that after fusion with nitre and carbonate of soda, the portion in- 
soluble in water be digested with hydrochloric acid, and the amount of 
undecomposed ore be “deducted from the original quantity. iat 
This may serve for the analysis of pure homogeneous specimens, 
but the common varieties are generally more or less mixed with 
substances and often with silicates of alumina and ma nesia 
lighter than the ore; in the process of elutriation consequently, 1 
tion of finely divided ore obtained suspended in the water, will 
a larger proportion of the impurities than deat which remains at iis 
bottom of the vessel. Again, when the powder thus obtained is fused 
with an alkaline carbonate, the silicates are at once attached while the 
portion which remains to be deducted after the action of both alkalies 
and acid, is pure chromic iron. In this way a specimen of impure ore 
— give a per-centage of. oxyd of chromium considerably below 
the truth 
While endeavoring to find some more eligible mode of treatment, it 
occurred to me that the bisulphate of potash 1 might be used with advan- 
, and in this I was not disappointed ; for 1 found that with certain 
Precautions, the mineral might be completely decomposed by it. The 
chromic iron must first be very finely levigated; (a gramme of the 
crushed ore will bhai fifteen or twenty minutes trituration in an agate 
mortar ;) it is then to be mixed with ten or twelve times its weight of 
fused bisulphate of potash and the mixture heated to fusion in a plati- 
num crucible ~ prmareh at a gentle red heat for about thirty min- 
utes. erucible and its contents when cold, oy Sat in water 
which with the aid of heat soon dissolves the saline The greater 
art of the chromium is left as a greer basic s sulbnane, insoluble in 
water or hydrochloric acid, and apparently identical with that obtained 
_ when any salts of elironsiines are heated with an excess of strong sul- 
_ phuric acid. 
: have found it the best mode of treating this mixture of soluble and 
insoluble salts, to boil the whole for a few minutes with an excess of or 
bonate of potash or soda which precipitates the — ot cbromt 
pod that may be in solution, and decomposes the insolu sulphate 
not easy, however, in this way to remove all the anit acid, 
sak degratdes the residue quite soluble in hydrochloric acid, but this 
