390 Eliot and Storer on Arsenic as 
- This question now — itself: In presence of an excess of zine, 
is not arsenic retained in the black residue (lead) from zine dissolved in 
dilute acids, in such a maaieien that it is not attacked by the acids or 
by the hydrogen, and therefore escapes detection? To determine this 
point, if possible, we dissolved 40 grammes of the Vieille Montagne zine, 
which had showed no trace - arsenic by Marsh’s test in dilute sulphuric 
acid, free from arsenic. The residue obtained was washed, treated with 
mixture thus obtained was washed into the flask of Otto’s apparatus, 
whose previous — of zinc and acid had vier thoroughly tested @ 
blane and found pure. At the end of the second hour, a very slight 
deposit was dinsbenibhe on close inspection in shee — tube, but the result 
was too doubtful to warrant the assertion that arsenic was contained in 
the insoluble residue. We next tried the same spell nt with Silesian 
pre in — Marsh’s test had detected arsenic. The residue Meee rr 
iments point is, that when a when sample of zine plete arsenic, & 
ersey 
zine, beca ause that eo itself contained arsenic, and its residue paige 
metallic copper, which would inevitably retain arsenic, as in Re insch’s 
test. The Pennsylvanian zine gave no residue with acids. 
The absolute necessity of obtaining zine free from arsenic for many 
pre investigations, renders any process for purifying zinc from arsenic 
ter of considerable interest and ne i ote We therefore "eied the 
ae of purifying zine by fusing it with one fourth of its weight of 
re ara a method fully described by Meillet,* but previously suggested by 
Orfila:+ 760 grammes of Silesian zine were fine ated and mixed 
with one fourth this weight of saltpetre, by placing the zine and nitre 1 
alternate iayers in a Hessian crucible. "The mixture was heated 
deflagration ensued, leit the melted mass was ote into cold water to 
separate the slag, caustic potassa, and any arseniate of potassa wh * 
have formed. The washed mass was remelted, and seat granulat < 
n 
pi in Otto’s apparatus with pure acid, and 4 in n twenty minu 
t, which, at 
the. end of three quarters of an ‘hour, was a sufficient iden of t he 
of arsenic. The dopontt was as large as that eine from a 
same Silesian zinc, before it had undergone this process of fusion we 
sine It has already been stated, under the aperopelate te head; that 
* Dingler’s Polyt. Jour., 1842, lxxxiii. 205; from Jour. de Pharmacie, 1841, p. 625: 
¢ Annales d’H ygiéne Publique, 1839, xxii, 4277. 
