an Impurity of Metallic Zinc. 391 
process did not disembarrass the zinc of the sulphur which it contained, 
and there seems to be little reason for expecting the complete removal of 
the arsenic, inasmuch as the fused saltpetre can only be brought in con- 
tact with the external surface of the zinc, however finely the metal may be 
granulated. It is not inconceivable that a trace of arsenic in a zine 
should be eliminated by Meillet’s process, and that a sample, originally 
almost absolutely free from arsenic, should be so improved as to afford no 
perceptible mirror; thus Stein* could not detect arsenic in a sample of 
zine purified by this method, but as a general rule it will not be safe to 
rely upon this process for the conversion of arsenical commercial zine into 
zine fit for use in Otto’s apparatus. 
On this subject of arsenic in commercial zine two opposite errors de- 
mand notice. On the one hand not a few chemists have maintained that 
commercial zine almost invariably contains arsenic, and that Marsh's test 
chlorid of gold; this solution was partially decomposed by the arse- 
Tluretted [sulphuretted ?] hydrogen, and when the zine had been com- 
Pletely dissolved, the chlorid of gold solution, which was supposed to 
Contain all the arsenic of the zinc in the condition of arsenious acid, was 
her decom 
the solution of arsenious acid, distillation was resor rt in 
Which the residue from the distillation remained we hed out with 
Water acidulated with chlorhydric acid, and the liquid so obtained was 
added to the original distillate, through which sulphuretted hydrogen was 
* Jour. f. pr. Chem, 1851, lili, 40. + Ann. de Ch, et Phys, [3], 1844, x, 507, note. 
¢ Ibid, (2), 1840, lxxiv, 432. 
