RESEARCH FOR ARSENIC AND ANTIMONY. 
97 
found that Antimony formed an obstacle to the application of 
his process, as it did to that of Marsh. Tin and lead were 
not deposited under the circumstances ; bismuth, mercury, 
and silver were deposited on copper, but in such a form as to 
create no difficulty to the analyst. The only serious objec¬ 
tion was found to exist in antimony. This metal was preci¬ 
pitated on copper under precisely similar circumstances to 
arsenic. The colour was iron-gray, or, when the antimony 
was in very small proportion, of a peculiar reddish or violet 
tint. Reinsch placed great reliance upon this colour as evi¬ 
dence of the presence of antimony. It is always procurable 
by sufficiently diluting the antimonial liquid, or by reducing, 
if necessary, the proportion of antimony present. To dis¬ 
tinguish by some positive characters the antimonial deposit 
on copper when it had acquired the iron-gray lustre of arsenic 
was a problem left unsolved by Reinsch. He merely states 
that, if the copper, having on it the antimonial deposit, be 
heated, a white, amorphous film of oxide of antimony is 
sublimed in place of the well-marked crystalline sublimate 
yielded by the arsenical deposit on copper under similar cir¬ 
cumstances. His process, therefore, in reference to antimony, 
was very imperfect. It served only to reveal the presence of 
arsenic, either when existing alone or when combined with 
antimony and deposited with it on copper. I have found, 
in operating on mixtures of small quantities of arsenic and 
antimony—when the acid liquid has been brought to the 
boiling point, and polished copper.is plunged into it—that 
the antimony is first deposited in a violet film, which rapidly 
loses its colour by increasing in thickness/and by becoming 
coated with a layer of metallic arsenic. When heat is applied 
to the copper having on it a deposit of antimony or arsenic, 
or a mixture of the two, it will be found that arsenic is more 
easily volatilized. A heat of about 380° to 400° is sufficient 
to produce a crystalline sublimate of arsenic, and at this 
temperature antimony remains fixed: hence, in addition to 
the colour of the film, its fixedness at a moderate heat be- 
comes an additional criterion of its antimonial nature. 
One of the most simple and satisfactory methods of dis¬ 
tinguishing the deposit of antimony on copper from that of 
arsenic is to boil the copper in a weak solution of potash, 
containing no lead as impurity. This method was suggested 
by Mr. Watson, of Bolton, and was first employed by him 
in medico-legal analysis. By agitating the copper in the 
alkaline liquid, and occasionally exposing it to air in the 
tube in which the experiment is performed, the metallic 
antimony is rapidly oxidized and converted to a soluble anti- 
