464 
CHEMICAL ANALYSIS. 
this fact, and from the ammoniacal gaseous compounds evolved 
from an aqueous solution of a liver impregnated with arse- 
nious acid, and undergoing spontaneous decomposition, I sa} r , 
that chloride of calcium is a proper and delicate test, forming 
a soluble chloride of ammonium and a precipitate of arsenite 
of lime. The criticism applied to the fourth test in my paper 
is confined to the assertion that it is never used by chemists, 
even as a corroborative test for arsenious acid, beino; liable to 
so many sources of error. Chemists and toxicologists are 
generally agreed that, singly, any one of the tests previously 
mentioned is liable to sources of error; but when they all cor¬ 
roborate one another, as in this case, very grave suspicion 
ought to exist in the mind of the analyst that arsenious acid 
is present, in the next place, in the letter alluded to, Reinsch’s 
test, as described in my paper, is admitted as reliable evidence 
as to the presence of arsenic in the tissue of the organ sub¬ 
mitted, but it is further remarked, in the same paragraph, that 
I did not state whether the sublimate obtained by heating the 
copper coated with a dark, steel-gray crust, was crystalline 
or amorphous. I may be allowed to state that the crystals 
were observed, and the omission of the word crystalline in my 
paper is due to me. Still further on, in the same paragraph, 
Professor Tuson applies a direct inference that no green pre¬ 
cipitate (Scheele*s green) was developed from the solution of 
the sublimate being treated with ammonio-sulphate of copper, 
as the solution contained free acid. To this conclusion I (to 
use Professor Tuson’s own words) need only remark, that 
the drop or two of free acid was driven off by heat over the 
flame of a spirit lamp, which was applied for that purpose 
and for hastening the solution; but supposing the green pre¬ 
cipitate had not developed itself on the solution being treated 
with that reagent, we could have got over the little difficulty 
by adding a single drop or two of a dilute solution of caustic 
potash. This brings me to the concluding paragraph in Pro¬ 
fessor Tuson*s letter, where he expresses himself to the effect, 
“ that the incorrect manner in which the chemical analysis, 
as described in my paper, was conducted, had been the 
cause of troubling you with the remarks in his letter, and 
also, as Professor of Chemistry to the English Veterinary 
College, he should have been omitting a duty had he 
remained silent on so important a matter, and one in which 
the liberty of the subject may possibly become involved. In 
reply to these assertions, and with due respect to i roressor 
Tuson, in the high and honorable position he stands, I 
think, if he had looked over the history of the case, as recorded 
in my paper, and had taken into consideration the time that 
