392A Eliot and Storer on Arsenic as 
then passed. The precipitated sulphid was collected on a filter, dried, 
and redissolved in ammonia ; this ammoniacal solution was then evap- 
senic,” and the other reagents are said to be pure. The methods by 
silver by a stream of hydrogen generated by the zinc under examination, 
but though his process was ner eee to that of Schauefele, he was led 
to the diametrically opposite conclusion. Again, Schauefele’s second 
method was essentially the process which has been thoroughly studi by 
Jacquelain, who claims for it @ delicacy* equal to that of Marsh’s pro- 
cess; and yet in Jacquelain’s own hands this method detected no arsemie 
in the specimen of zinc which he examined.} We cannot avoid the con 
clusion, that the determinations given in M. Schauefele’s thesis have no 
general significance, and have gained more credit than they deserve. a 
are not contaminated with arsenic, and it should be noticed that, ' 
one of our pure samples (the Pennsylvanian) was of a zinc which aa 
et manufactured in large quantities, the other was a specimen OF © ‘ll 
ian zinc, one of the most common and abundant of the commer! 
' We turn now to the discussion of the opposite error, namely, that a 
senic is very rarely to be found in the zinc.of commerce. On this 
_ we need only quote the strong statements of the highest authorities. vy 
nault, in the reportt to the French Academy on Marsh’s process a al 
modifications, wrote : “It is easy to procure in commerce zinc and ® 
* Ann. de Ch..et Phys, [3], ix, 490. Ibid., 1843, [3], vii, 189. 
_ $ Comptes Rendus, Teil, sore, id dees tb Gia ode Phys, [3], Hi, 159 
