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SELECTED ARTICLES. 
rate on small quantities, and the metal cools too rapidly to 
assume the texture of large plates, such as the antimony of 
commerce presents. 
Antimony entirely devoid of arsenic, when thrown on in- 
candescent coals, gives off vapors which are entirely without 
odor. However small may be the alloy of arsenic, the vapor 
still assumes the alliaceous odor. This method is perhaps the 
most delicate for recognising the presence of arsenic in antimo- 
ny. The process proposed by M. Serullas, and adopted by the 
authors of the new Codex, is likewise of great sensibility; but 
the process of Marsh, which is so sensible when searching for 
arsenic in a free state, or in combination with oxygen, is to- 
tally insensible when the object is to detect arsenic in metallic 
antimony. 
In fact, if we introduce into the apparatus of Marsh, anti- 
mony of commerce containing arsenic, and giving rise to a 
strong alliaceous odor on burning coals, dull black metallic 
spots will be obtained, which, although they may contain 
more arsenic than the antimony from which they were deriv- 
ed, will react with agents absolutely as if entirely of pure an- 
timony. Formed on plate of porcelain, and treated by one or 
two drops of nitric acid, they furnish, after the excess of acid 
has been driven off by heat, a residue which, touched by ni- 
trate of silver, produces no red color which indicates the pres- 
ence of arsenic; but if, after treatment with the nitrate of sil- 
ver, we add to the residue a drop of ammonia, in an instant 
there is formed a beautiful black color, which M. Orfila states 
to be a character peculiar to antimony, and very suitable to 
distinguish it from arsenic. 
Thus the arsenic which exists in the spots which are ob- 
tained by placing in the apparatus of Marsh, arsenical anti- 
mony, is concealed, and is not to be detected by those means 
which are useful when it is isolated. This is owing to the 
circumstance, that when arsenical antimony is treated by ni- 
tric acid, the arsenious or arsenic acid which is formed by the 
oxidation of the arsenic, does not remain in a free state; it 
combines with the antimonious acid, and is thus withdrawn 
