414 
RESEARCH FOR ARSENIC AND ANTIMONY. 
gauze, foil, or wire. The copper was entirely dissolved by 
the aid of hydrochloric acid and a weak solution of chlorate 
of potash. The surplus chlorine was removed by the gradual 
addition of small quantities of bisulphite of soda, and the 
sulphurous acid derived from this salt was removed by boil¬ 
ing—the freedom of the vapour from the acid being indicated 
by holding in the current, starch-paper saturated with iodic 
acid. Reinsch’s process was then applied to the liquid, and 
if the copper under examination contained arsenic, a deposit 
of arsenic was obtained in the usual way on a piece of 
copper. 
There is no chemical objection to this method; but seeing 
that several substances are employed in the analysis, and 
that a mixture of salts resulted, it appeared to me preferable 
to convert the copper to a soluble chloride by digesting it in 
pure hydrochloric acid alone, and then, from the known vola¬ 
tility of chloride of arsenic, to separate this from the chloride 
of copper by distillation. For this purpose, I found it neces¬ 
sary to expose the copper in a stratum of pure and concen¬ 
trated hydrochloric acid contained in a saucer, the metal 
being partly immersed in the acid and partly exposed to the 
air. After two or three days’ exposure, according to the 
thickness of the metal, a brown liquid (a solution of sub¬ 
chloride of copper in hydrochloric acid) was obtained. In 
some experiments, the copper was entirely dissolved; in 
others, a portion was left. The weight of the residue, after 
washing and drying, deducted from the original weight em¬ 
ployed, gave the amount of copper dissolved. The brown 
liquid was distilled to dryness in a flask or small retort, 
placed in a sand-bath, and the vapour was condensed in a 
flask or receiver containing a small quantity of distilled 
water. A perfectly clear solution of chloride of arsenic, or a 
mixture of hydrochloric and arsenious acids, was thus pro¬ 
cured. When one part of this distillate was diluted with its 
volume of water and boiled, and a small piece of pure polished 
copper was introduced, the presence of arsenic was speedily 
indicated by the characteristic deposit on the bright metal. 
Another portion of the liquid was introduced into a Marsh’s 
apparatus, or a small flask with a bent tube fixed in its neck, 
and by the addition of pure zinc, arseniuretted hydrogen was 
easily procured from it and tested. When to a third portion 
a solution of chloride of gold was added, and the mixture 
boiled, the gold was, after a time, completely deposited. The 
weight of gold thus deposited supplies one method of calcu¬ 
lating the quantity of arsenic present in the distillate. 
Of the delicacy of this process for detecting arsenic, there 
