66 ON THE IMPURITIES OF COMMERCIAL ZINC. 
previous experiments made by Prof. Brush we had learned that some specimens of this 
spelter contain noticeable quantities of Cadmium. 
Tron—is usually to be found in commercial zinc, and enough quantitative deter- 
minations of the amount of this impurity have been already published to show 
that it very rarely exceeds in amount two tenths of one per cent, and that, more- 
over, it is an impurity introduced into the zinc from the iron moulds in which the 
spelter is generally cast. Karsten, in his admirable memoir on the “ Admixtures which 
diminish the Tenacity of Zinc," has sufficiently proved that the zinc takes up iron from 
the moulds, by determining the iron in the zinc before and after the process of casting. 
It is true that Karsten experimented upon Silesian zinc alone, but the same contami- 
nation of the spelter would be produced in any works in which the process of casting 
in iron moulds was used.* We have made determinations of the iron in three samples 
of zinc volumetrically by permanganate of potassa,t but have thought it not worth 
while to multiply analyses upon a point already sufficiently clear. , 
1. New J eid zinc gave 0.2088 per cent of iron. 
e Aude To anou oq wee Rg Wy nt 
3. Mint vilo? - 7 «00085 e « 
din eio BRE ODODE e « 
5. Berlin zinc (sheet) * ^ 0.0674 ei S 
RI de EE DEER EN 
Besides the metallic impurities which have already been mentioned, it has been 
stated by previous observers, in places already cited, that nickel, cobalt, manganese, 
arsenic, and antimony are sometimes to be found in the zinc of commerce. The pres- 
* Karsten determined the iron in three samples of * Werkzink," by which term he designates the zinc 
which is the immediate product of the distillation, —a mass of drops partially fused together; and again de- 
termined the iron in the same samples after they had been east into cakes, and converted into the crude zinc 
(Rohzink) as it is found in commerce. His results may be tabulated as follows : — 
Iron in the Iron in the 
Werkzink. Rohzink. 
Bei -. : ` . 0.03 per cent. 0.154 per cent. 
we 2, Ld . . H 0.04 « ed 0.180 € S 
“3, . S . e 008 "*. 4 Cae 2% 76 
Karsten also shows that the refined zinc, obtained by remelting the crude zinc on the hearth of a reverbera- 
tory furnace, is almost absolutely free from iron. Archiv. f. Mineralogie, Karsten u. Dechen., 1842, XVI. 
623. Also, Dingler’s Polyt. Jour., 1842, LX XXVI. 193. 
t For the description of the method, see Mohr’s Lehrbuch der Titrirmethodo, Zweite Abtheilung, p. 234. 
A sample of zinc from Stolberg gave Mohr 0.0442 per cent of iron, anda sample from Linz, on the Rhine, 
contained 0.126 per cent of iron. 
