ON THE IMPURITIES OF COMMERCIAL ZINC. 63 
To verify the results stated in the third column of Table L, we determined the 
sulphuric acid in each precipitate of sulphate of lead, by the method described by 
Fresenius.* Each precipitate of sulphate of lead was digested with a solution of pure 
bicarbonate of soda prepared from the oxalate, and the sulphuric acid determined in 
. the usual manner in the filtrate from the washed carbonate of lead. A comparison of 
columns 3 and 5 in Table IIT. made it at once clear that the precipitates of column 
2 consisted only of sulphate of lead. 
TABLE II. 
a) QJ (8) (4) (5) 
Sulphuric Acid Sulphurie Acid 
Name of Zine. Dog in the Given Weight of P0 s oc in the ound, Weight of 
gram 
Silditad geg 0.5082 0.1341 0.3954 0.1359 
Vieille Montagne . 0.108 0.0285 0.0845 0.029 
New Jersey . A S 0.033 0.0087 0.035 0.012 
Mint k e e 0.1768 0.0463 0.1356 0.0466 
Rousseau Fréres 0.0379 0.0100 0.0306 0.0105 
Berlin S 0.4381 0.1156 0.3331 0.1146 
Wrexham $ 0.5235 0.1382 0.4282 0.1469 
Mines Royal . 0.469 0.1238 0.3659 0.1255 
Dillwyn & Co. 0.771 0.2035 0.5962 0.2045 
Messrs. Vivian . 0.6165 0.1627 0.4780 0.1640 
Cadmium and Tin. — The filtrates from the precipitates of sulphate of lead obtained 
from the zincs in Table L, except the Pennsylvania zinc, were saturated with sulphu- 
retted hydrogen for twenty-four hours or upwards, and the small precipitates which 
separated were filtered off, washed quickly with sulphuretted hydrogen water, dried, 
and ignited ; they were then treated with a few drops of nitric acid, again evaporated 
to dryness, ignited, and weighed. The color of these precipitates was yellowish-brown, 
with the single exception of the precipitate obtained from New Jersey zinc, which was 
blackish. When this blackish precipitate from this zinc was moistened with nitric acid, 
the blue-green color of the partial solution suggested the presence of copper, and a 
separate determination of the amount of copper in this zinc was therefore made, and 
will be given hereafter. The color of the precipitates from the other zincs excluded all 
the metals of the group precipitated by sulphuretted hydrogen, except arsenic, anti- 
mony, tin, and cadmium. The first two of these metals do not exist in zinc, as we 
shall hereafter show, except in exceedingly minute quantities, and even any such minute 
quantity would probably have been driven off by the ignition, twice repeated, of the 
$ Anleitung zur Quantitativen Analyse, Braunschweig, Vierte Auflage, 1858, p. 286, $ 132, IT. b. f. 
