ON POISONING BY ARSENIOUS ACID, 
329 
color, which may be deprived of color or at least brought to 
the state of a yellowish white residue, by repeated boilings 
with small proportions of strong nitric acid. This residue, 
cooled and touched with a drop of nitrate of silver, assumes a 
yellow similar to that of phosphate of silver, and not a brick- 
red color. 
The arsenical spot, on the contrary, immediately disap- 
pears in cold nitric acid, and if the liquid be evaporated, 
arsenic acid remains, with which nitrate of silver will instanta- 
neously produce a brick-red color. 
A complete solution of the question, whether it is possible 
to obtain spots, such as are spoken of by MM. Flandin and 
Danger, by carbonizing the intestines of individuals not 
poisoned, and introducing an aqueous decoction of the residue 
into Marsh's apparatus? is to be found in the fact that if the 
carbonization be complete, and performed according to the 
rules laid down, then the sulphite and phosphite of ammonia 
which may exist in the organic matter is transformed into 
sulphate and phosphate of ammonia, which do not afford 
the slightest spot with the apparatus of Marsh. This result is 
so well known that it is useless to support it by new proofs. 
But, it constantly happens that when the organs of a person 
poisoned are comptelely carbonized, if the organ had retained 
any of the poison, a greater or less number of arsenical spots 
may be obtained. 
M. Orfila spoke concerning spots far more important than 
those noticed by MM. Flandin and Danger because they bear 
more resemblance in their physical character at least, to 
arsenical spots. He exhibited several plates upon which were 
found the spots obtained, whether with bichloride of mercury, 
with chloride of tin or of lead, or finally with sulphate or 
chloride of zinc. It is sufficient to introduce any of these into 
the apparatus of Marsh, acidulated either with sulphuric or 
hydro-chloric acid, and to act with a strong flame, to collect 
on a porcelain plate, brilliant, shining black spots, similar in 
color to arsenical deposits. These salts are carried up with 
the hydrogen gas, deposited on the plate and decomposed by 
VOL. VII. — NO. IV. 42 
