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mr. Harrison’s cases of poisoning, etc. 
2ndly. That even supposing Messrs. Harrison and Walton 
succeeded in dissolving out arsenic from the liver in the way 
they describe, the solution obtained would be so largely con¬ 
taminated with foreign substances as to render it unfit for 
the application of the ammonio-sulphate of copper and the 
ammonio-nitrate of silver tests. These tests should he applied 
to a pure aqueous solution of arsenious acid only. 
Mr. Harrison enumerates two other tests which are quite 
new to me as indications of the presence of arsenic, although 
I have been engaged in analytical chemistry for the last 
fifteen years. These tests, which were applied to the 
aqueous solution of the liver, are as follows: 
ct 3rdly. Chloride of calcium, a white precipitate. 
u 4thly. Caustic potash, with excess of ammonia, being 
added to a portion, it was treated with a solution of sulphate 
of copper. On the application of heat, the red suboxide of 
copper was deposited at the bottom of the tube, indicative of 
arsenious acid, but valuable only so far as corroborating the 
previous tests.” 
Chloride of calcium will not give any precipitate with an 
aqueous solution of arsenious acid. 
Although a solution of arsenious acid in water will pre¬ 
cipitate red suboxide of copper when boiled with a mixture 
of sulphate of copper, potash, and ammonia, this reaction is 
never made use of by chemists, even as a corroborative test 
for arsenic, as it is liable to many sources of error. 
The only analytical evidence upon which any reliance can 
be placed is to be found in the concluding paragraph where 
Reinsclfs test for arsenic is described. But even there the 
author does not state vdiether the sublimate which he 
obtained by heating in a tube—the copper c: coated with a 
dark, steel-grey crust ”—was crystalline or amorphous. The 
sublimate of arsenious acid invariably assumes the form of 
octohedral crystals, which is highly characteristic of that 
substance. In order to obtain corroborative testimony rela¬ 
tive to the sublimate being really arsenious acid, Mr. 
Harrison says that he dissolved it in “ water acidulated with 
a drop or two of hydrochloric acid . This was now treated with 
ammonio-sulphate of copper, when we had the green pre¬ 
cipitate, as before stated, with the neutral solution.” With 
reference to this last test, I need only remark that no 
green precipitate (Scheele’s green) could possibly have deve¬ 
loped itself while the solution to which the ammonio- 
sulphate of copper was added contained free hydrochloric 
acid. 
1 cannot conclude without expressing my great regret that 
