84 . REPORT—1840. 
of acids. All the specimens of commercial zine that the author had 
happened to try, were found to contain arsenic. 
Pure muriatic acid, diluted with distilled acid, is poured upon the 
metal, and the hydrogen evolved is passed first through a solution of 
nitrate of lead, and next through a solution of nitrate of silver. 
Nitrate of lead seems not acted upon by arseniuretted hydrogen, at 
least when in very small proportion ; but were any sulphur present in 
the metal, hydrosulphuretted hydrogen would be evolved in conse- 
quence, and the solution of nitrate of lead would be blackened, which, 
however, the author did not observe ever to occur. But nitrate of silver 
seems immediately to be acted upon by most minute portions of arseniu- 
retted hydrogen. A bluish-black precipitate is formed, which, to 
judge from a qualitative analysis, appears to be an arseniuret of silver. 
This bluish-black precipitate may be collected with remarkable facility, 
from its falling readily from the solution, which it leaves perfectly 
clear. Heated in a small tube, so that the matter heated comes into 
contact with the air, the bluish-black precipitate evolves arsenious 
acid, which, by the liquid tests, may be further satisfactorily recog- 
nized. Antimony produces a similar precipitate, so that the mere 
appearance of the precipitate is not enough, without the production 
and recoguition, by the usual methods, of the arsenious acid. 
By a few evident modifications, this method may be applied te 
medico-legal investigations. 
—————— 
On the Tests for Sulphurie Acid when thrown on the Person. 
By R. D. THomsoy, M.D. 
The object of the author was to discuss the accuracy of the modes of 
testing sulphuric acid when employed for criminal purposes, and espe- 
cially when thrown on the person. A case had lately occurred to him 
in practice, and which was brought before the last session of the 
Central Criminal Court, which proved that the mode of determining 
the presence of free acid by mere testing was by no means satisfactory. 
A woman, in a fit of rage, threw a quantity of oil of vitriol at the face 
of a cabmaster in the neighbourhood of Euston-square, and before the 
unfortunate sufferer could wash off the acid only two minutes had ex- 
pired; yet the consequence was loss of vision intheeye. The author stated, 
that having attentively considered this case, and made a series of 
experiments on the eyes of dead animals, he had discovered that this 
kind of blindness was perfectly curable ; and he had accordingly pro- 
posed an operation for this purpose ina paper read at the Medical 
Section. But, besides having his face injured, the hat of the man was 
discoloured also with the acid. This article of dress was sent to the 
author, to determine the nature of the agent in this work of destruc- 
tion. The result of his experiments was, that both the injured and 
entire hat contained sulphuric acid, as tested by nitrate of barytes ; 
and a solution of the soluble matter of both states of this article of 
dress, afforded an acid reaction. It was therefore necessary to adopt 
