68 
SELECTED ARTICLES. 
Having washed the hydrate in distilled water, it was dis- 
solved in hydrochloric acid, and the liquid treated by a cur- 
rent of sulphuretted hydrogen; a yellowish brown precipitate 
was formed, which, when washed and dried, yielded, by the 
aid of heat, metallic tin. 
One hundred and twenty drachms of the salt yielded .0285 
of a drachm of dry sulphuret of tin, or about two ten-thou- 
sandth parts of tin in a pound of sulphate of iron. The pre- 
sence of tin in this product might have been accidental; but 
another specimen, likewise labelled pure sulphate of iron, and 
which came from another manufactory of chemicals, having 
yielded it, I procured various commercial specimens. The 
precipitates obtained by means of sulphuretted hydrogen, 
in their filtered solutions varied singularly in color and com- 
position. When the salt contained much peroxide, the pre- 
cipitate was loaded with a great quantity of sulphur; having 
been filtered, Washed, and dried, it was introduced into a tube 
closed at one end and heated, to volatilize the sulphur. The 
sulphuret which remained, treated with charcoal and soda, 
aided by heat, gave immediately metallic globules. This 
metal was sometimes of a bright silver white, more frequently 
it had a red reflection, and sometimes the color of copper. 
Nevertheless, an examination of this last, by solution, &c. 
always proved the presence of tin. It is thus easy to con- 
ceive, that in this last case we ought always to find tin in the 
hydrate, since during its preparation copper would remain in 
the solution. 
The influence of Tin in the determination of small quan- 
tities of Jirsenic. 
If we dissolve by heat 995 parts of good tin in hydrochloric 
acid, mixed with a little nitric acid, and add to it five parts 
of arsenic and then boil, we will have a liquid from 
which it is not possible, by ordinary means, to obtain metallic 
arsenic. 
A solution, containing 990 of tin, to ten of arsenic, fur- 
