RESEARCH FOR ARSENIC AND ANTIMONY. 
293 
Hydrochloric acid, diluted with from six to ten parts of 
water, has but a feeble action on copper, even after long 
boiling. A trace of this metal may, under these circumstances, 
be found in the liquid. If, however, the oxide of arsenic or 
antimony should be present in the liquid, a portion of copper 
is immediately dissolved, and an equivalent portion of arsenic 
or antimony is deposited. So soon as the copper is com¬ 
pletely coated, the solvent action is arrested. In order to 
determine how far arsenicated copper is liable to undergo 
solution, and to set free arsenic as a result of boiling in pure hy¬ 
drochloric acid diluted, the following experiment was performed. 
A quantity of copper-foil and gauze, equivalent to 39*4 grains 
in weight, was boiled in a retort with a mixture of one ounce 
of pure hydrochloric acid and eight ounces of water. The 
boiling was continued for half an hour, and the distilled acid 
liquid was collected in a cool receiver. This amounted to 
twelve fluid drachms. It contained no trace of copper; and 
onacareful examination of the liquid by Marsh’s and Reinsch’s 
processes, there was not the slightest trace of arsenic in it. 
The large quantity of acid liquid left in the retort was found 
to contain a small quantity of copper; but there was no arsenic 
dissolved in it. The undissolved copper, when washed and 
examined by the microscope, had no metallic deposit upon it; 
it was unchanged in colour, but presented slight marks of 
corrosion. A quantity of it heated in a tube gave no subli¬ 
mate. 
When arsenicated copper is boiled in the diluted acid for 
five minutes—a period within which arsenic, if present, is 
commonly manifested by some deposit or change of colour on 
the surface of the metal—no copper is dissolved. The metal 
retains its usual polish and lustre. If a small portion of 
oxide of arsenic or antimony be now added to the boiling acid 
liq uid, there is an immediate deposit on the clean copper 
surface ; and copper, in small quantit} r , will be found dissolved 
in the liquid by that delicate test, ferrocyanide of potassium. 
It is, therefore, obvious that the metallic oxide (i. e. the poison 
itself) brings about the solution of the copper, but not to an 
extent to eliminate arsenic so as to affect the process. It has 
been alleged that the accidental presence of certain salts, or 
organic liquids not containing arsenic, would lead to a suffi¬ 
cient solution of the copper to give rise to a deposit of arsenic 
on that metal. This action has been looselv ascribed to alka- 
line nitrates, phosphates,sulphates, andchlorides,—salts which 
dissolved copper. In the other instance the copper was not dissolved, but 
was coated in a few minutes, as is usual in cases in which arsenic is actually 
present a9 a poison. 
