226 
Selected Articles. 
execution, as a minute is sufficient to determine the purity of 
a hydrochloric acid, without trouble and without expense. It 
is so delicate, that a hundreth of sulphurous acid will not 
escape detection. 
I have learnt that many manufacturers who obtain hydro- 
chloric acid charged with sulphurous acid, get rid of it by 
passing a certain quantity of chlorine through it, which trans- 
forms the sulphurous into sulphuric acid; this is one reason 
why certain of the hydrochloric acids of commerce contain 
so much sulphuric acid. — Journ. de Pharm. 
ART. XLVIL ACTION OF TANNIN ON ORGANIC SALIFIABLE 
BASES, &c. By O. Henry. 
Among the characteristic properties of the alkaloids, or 
vegetable alkalies, there is one peculiar to the whole of them — 
their precipitation by an infusion of galls. This character, 
which was noticed by M. Dublanc, Jr., as a test for morphine, 
is applicable to many of the other alkaloids in a far more 
striking degree. Is this effect attributable to the tannin or to 
the gallic acid? This does not appear to have been fully ex- 
plained, and it was therefore with the hope of throwing some 
light on the subject, that I undertook the following experi- 
ments. 
M. Pelouze, in his interesting memoir on tannin, has shown 
that this body forms almost insoluble precipitates with qui- 
nine, cinchonine, morphine, iodine, narcotine, strychnine, ani 
brucine. At the time of the appearance of his memoir, I was 
endeavouring to discover an exact and yet expeditious mode 
of determining the quantities of quinine and cinchonine con- 
tained in the Peruvian barks of commerce. Pure tannin, it 
