ON THE IMPURITIES OF COMMERCIAL ZINC. 93 
those samples which we have examined, of the spelters which are produced in the 
largest quantity from the best ores. An extended examination of the zincs produced 
on a small scale at different works throughout Germany, would in all probability detect . 
the same impurities; * but the labor of the investigation would be out of all proportion 
to the interest and importance of the facts to be observed. 
Belgian Zinc. — There is a very noticeable difference in the purity of different sam- 
ples of Belgian zinc. The ore is a mixture of carbonate and silicate of zinc, and 
yields with care an excellent spelter, which contains but a small amount of lead and 
no arsenic. We have found other samples of the zinc that were not free from arsenic, 
which they probably derived from the blende and its associated minerals, which occur 
with the silicate and carbonate of zinc constituting the great bulk of the ore. Careful 
selection of the ore is evidently necessary for the purity of the resulting metal. 
English Zinc. — Much of the English zinc is made from blende, and is therefore 
more impure than the zinc of other countries made from better ore. Our analyses 
show that the English zincs, on the average, contain more lead than any spelter except 
the Silesian, and we also found much more arsenic in them than in any other zinc, 
except perhaps the New Jersey. One specimen of English zinc yielded a clear but 
slightly colored solution in dilute sulphuric acid, and our subsequent analysis gave no 
explanation of this color; its general appearance suggested the possible presence of 
some organic matter in the solution, and we mention the circumstance, because it is 
the only clew which we have been able to find to Miller’s remark previously quoted, 
namely, that zinc contains a peculiar carbonaceous matter. , 
American Zinc. — The New Jersey zinc is made from the red oxide of zinc, mixed 
with Franklinite, and from the published analyses of these minerals the natural in- 
ference would be that they should yield a zinc of excellent. quality. Accordingly, we 
found that our sample of this spelter contained less lead than any except the Penn- 
sylvanian zinc; but on carrying further the analysis of the zinc, we were surprised to 
detect the presence of copper in a quantity sufficient to admit of quantitative determi- 
nation. The analyses of the ore afford no clew to the source of this copper, and we 
are unwilling to believe that it is a natural and necessary admixture in zinc prepared 
from this ore. The amount of arsenic contained in this spelter was unusually large, 
but is fairly derived from the ore, in which we detected distinct traces of arsenic. 
This zinc was also contaminated with sulphur, carbon, and tin, and on the whole was 
one of the most impure spelters which we examined. 
* For example, it would be difficult to imagine how a zine free from arsenic could be made from the oxide 
collected on the * Zinkstuhl? in the process formerly used in the Hartz, or from the arsenical blende now 
worked at Freiberg (Saxony). 
