60 : ON THE IMPURITIES OF COMMERCIAL ZINC. 
Pennsylvanian zinc (Pennsylvania and Lehigh Zinc Works, Bethlehem, Penn.). 
Vieille Montagne zinc, such as is used at the United States Mint. 
A zinc labelled * Zinc pur," Rousseau Fréres, Paris. 
A sheet zinc of unknown origin, obtained in Berlin ( Prussia). 
An English zinc, made near Wrexham, North Wales. 
. An English zinc, from the Mines Royal, Neath, Glamorganshire. 
10. An English zinc, from the works of Dillwyn and Company, Swansea. 
11. An English zinc, from the works of the Messrs. Vivian, Swansea. 
Our specimens of the first three spelters were obtained in blocks or ingots from the 
Revere Copper Company of Boston, by the kindness of John Revere, Esq.; we received 
our specimens of the fourth zinc in ingots, through Professor Brush of New Haven, 
directly from the manufacturers; the fifth zinc was procured in Philadelphia, by our 
friend, Professor J. P. Cooke, from the purveyors to the United States Mint. The sixth 
specimen was bought as pure distilled zinc, in 1856, at Paris, of MM. Rousseau Fréres, 
OMIA TE 
dealers in pure chemicals. The four samples of English zinc are authentic specimens, 
for which we are indebted to the kindness of the Hon. Edward Twisleton of Lon- 
don. The eighth specimen is a spelter made * from silicate of zinc" at Minera, near 
Wrexham in North Wales; Belgian retorts are used in its manufacture, but no other 
details of the process are known to us. 
A qualitative examination of the residues left by these zincs when treated with 
dilute acids, showed that they chiefly consisted of metallic lead. It will appear in the - 
sequel, that lead is the chief impurity of commercial zinc, and that the carbon, tin, 
copper, iron, arsenic, and other impurities found in it by previous observers, occur 
either in very minute quantities, or rarely, and doubtless accidentally. 
Lead. — We have determined quantitatively the amount of lead in each of the zincs 
above specified by the following process: — A weighed amount of each zinc was dis- 
solved in dilute sulphuric acid, saturated with sulphate of lead. This acid was pre- 
pared by diluting common sulphuric acid with four parts of water, and allowing the 
mixture to settle for some days before decantation. "When the zinc was dissolved, the 
black residue was in each case separated from the solution by decantation, treated with 
a few drops of nitric acid, and gently evaporated to dryness. The white residue thus 
obtained was then washed with the same dilute acid into the original solution of the 
zinc, which was filtered after standing forty-eight hours, and the precipitated sulphate 
of lead was weighed on a tared filter. The results of these analyses are given in the 
— table: — 
