ON THE IMPURITIES OF COMMERCIAL ZINC. 61 
TABLE I. 
a (2.) (3.) (4.) (5.) 
Name of Zino. abe ong PbO BO. Weight iol of Land. e ox 
grammes. gramme. per cent. 
Silesian i ʻ S 23.8066 0.5082 0.3472 1.46 
Vieille Montagne " "25.2796 0.108 0.0738 0.292 
New Jersey . . , 28.672 0.033 0.0225 0.079 
Pennsylvania. . 26.522 No residue. 0.0000 0.000 
Mint. 1 e ` 24.5308 0.1768 0.1212 0.494 
Rousseau Fréres 24.3432 0.0379 0.0259 0.106 
Berlin . ` $ e 23.074 0.4381 0.299 1.297 
Wrexham A ? 29.999 0.5235 0.3569 1.192 
Mines Royal ‘ S 38.8276 0.469 0.3197 0.823 
Dillwyn & Co. . ` 31.6425 0.771 0.5256 1.661 
Messrs. Vivian . S 27.724 0.6165 0.4203 1.516 
Two points in the process required examination. In the first place, it was unadvisa- 
ble to use pure sulphuric acid, because sulphate of lead is not absolutely insoluble 
in dilute sulphuric acid; but the question suggested itself, whether by employing acid 
saturated with sulphate of lead, we might not introduce lead which would subse- 
quently be weighed as sulphate. The following experiment answered this question. 
0.2198 gram. of pure lead (Probirblei from the laboratory of Professor Plattner in 
Freiberg) was dissolved in pure dilute nitric acid, the solution evaporated to dryness, 
the residue so obtained dissolved in hot water, and precipitated as sulphate in 250 c. c. 
of our dilute sulphuric acid (one part of commercial acid and four parts of water.) 
gramme. 
Weight of pure lead taken 0.2198 
ei * sulphate on a tared filter 0.3219 
*  * lead in 0.3219 gram. Pb O, SO, 0.2199 
After weighing the sulphate on a tared filter, we ignited the filter and precipitate, 
and, following the method of determining sulphate of lead which is prescribed in most 
text-books, again weighed the sulphate after ignition. 
gramme. 
Weight of pure lead taken 0.2198 © 
e * sulphate of lead after ignition — 0.3123 
«  * lead in 0.3123 gram. PbO, SO, 0.2134 
This result conclusively proved that none of the minute quantity of lead in the sul- 
phuric acid was weighed as sulphate at the close of the analysis. Secondly, it was 
necessary to inquire whether the insolubility of the sulphate of lead was diminished 
by the presence of a large amount of sulphate of zinc. To determine this point, a 
weighed amount of acetate of lead was dissolved in water, and added to a solution of 
