382 Eliot and Storer on Arsenic as 
to prepare a quantity of sulphuric acid in which the presence of arsenic 
could not possibly be suspected. To attain this object, we subjected a 
specimen of American sulphuric acid to the following process. The aci 
was first boiled with a little flowers of sulphur, as proposed by Barruel,* 
in order to free it from the nitrous fumes which the common sulphuric 
acid almost always contains; a small quantity of pure chlorhydric acid 
was then stirred into the cooled acid, which had been carefully decanted 
from the free sulphur, and the whole again boiled; to the acid, again 
i d 
pletely driven off, the second addition of chlorhydric acid being made, as 
has been recommended by H. Rose, in order to insure this result, Lastly, 
a portion of chlorine-water was added to the cooled acid to oxydize any 
sulphurous acid which might be contained in it, and after a third boiling, 
e cool and narrow part of the reduction-tube. With the same act 
and apparatus, 200 grammes of Pennsylvanian zinc (which had been pro 
ved to be altogether the purest zine in our possession) gave absolutely no 
deposit of any kind in the fine reduction-tube at the end of one hour, the 
time during which, in all our examinations for arsenic, we maintained & 
steady flow of hydrogen through the red-hot reduction tube. We had 
which subsequent experiment had proved to be free from that impurity. 
In order satisfactorily to establish these conclusions, it was neces 
prove by frequent repetition that the same result might always be expec- 
om two zines, an i vee 
dl 4, 
* Dingler’s Polyt, Jour., 1837, Ixiv, 55 ; from Jour. de Ch. Médicale, 1886, No- 
t Pogg. Ann., 1858, ev, 571. t Ann. der Ch, u. Pharm., 1855, xcl¥, se 
Ann. de Ch, et Phys,, 1843, [3], vii, 191. 
