64 ON THE IMPURITIES OF COMMERCIAL ZINC. 
precipitates. The small precipitates weighed must therefore have consisted of the 
oxides of tin and cadmium. The results of these analyses are given in the following 
table. The numbers in the fourth column show what per cent each weight in column 
3 is of the corresponding weight in column 2. 
TABLE IV. 
(1) e) (3) (4) (5) 
Weight of the Precipitate| In per cent of the Zinc : 
Name of Zinc. Weight of Zinc taken. | by HS, ignited with taken, these precipitates Result of the Blowpipe test for Tin. 
NO; * equal. : 
: grammes. gramme. ; 
Silesian 23.8066 0.013 0.0546 No tin, or but very uncertain traces. 
Vieille Montagne 25.2795 0.0071 0.0281 Distinct spangles, probably tin. 
New Jersey 28.672 0.1285 O41. |i sraa or AE 
Mint 24.5308 . 0.0024 0.0098 | Notin. 
Rousseau Frères 24.8432 0.0099 0.0406 Faint traces of tin. 
Berlin 23.074 0.0041 0.0178 Distinct spangles, probably tin. 
Wrexham 29.999 0.0021 0.0070 No tin. 
Mines Royal 98.8276 0.0016 0.0041 A very uncertain trace of tin. 
Dillwyn & Co. 31.6425 0.0011 0.0035 Faint traces of tin. ; 
Messrs. Vivian 27.724 ` 0.0079 > m 
If it be remembered that the weights given in the third column are not the weights 
of the metals themselves, but of their oxides, it will be apparent that tin and cadmium 
together form but a very insignificant impurity in commercial zinc. In none of the 
ten samples analyzed, except the New Jersey zinc, can the sum of the tin and cadmium 
amount to one twenty-fifth of one per cent. The precipitates whose weights are given 
in column 3 (except New Jersey, which alone gave indications of copper) having been 
moistened with nitric acid, were digested with distilled water, and then filtered. 
Through the filtrates sulphuretted hydrogen was passed, producing in each case a dirty- 
yellow cloudiness, which was too small in amount to be further examined. That por- - 
tion of each precipitate which was insoluble in water, and therefore remained on the 
filter, was examined before the blowpipe by incinerating the filter and precipitate on 
charcoal, and fusing them with neutral oxalate of potassa in the reducing flame. The 
fused mass was ground up in an agate mortar, and examined for metallic spangles ; 
when these were sufficient in amount, they were dissolved in chlorhydric acid, and the 
solution tested with terchloride of gold. The result for each zinc is stated in the fifth 
column of Table IV. For Silesian zinc, the Wrexham (English) zinc, and the zinc 
