» 
Means of detecting Arsenic in the Animal Body, rc. 279 
“Ast. Does the hydrated peroxide of iron contain arsenic ? 
2d. Does arsenic exist normally in the animal tissues ?- 
“3d. Is not. Marsh’s apparatus subject to serious objections? » 
Ath. What are the best means not only of ‘detecting but of 
mepisingtibe quantity of arsenic _— in combination with 
animal matte 
5th. What are the best means of aie the poisonous ~ 
effects of arsenious acid ? 
To all these questions such answers will be een as paEs yet 
been furnished. : 
Does arsenic exist in the peroxide of iron? 
This question originated from the fact that this oubeianes had 
been administered in the case spoken of ; and there are those who 
suppose that the arsenic detected belonged originally to the per- 
oxide of iron used as an antidote. 
It is well known that arsenic exists in a state of combination in 
many of the sulphurets of iron, from which the sulphate is ob- 
tained, and it is the latter that furnishes the peroxide either by 
precipitation or heat. Both forms of this oxide have been sub- 
jected to minute examination by M. Orfila, who was particularly 
interested in this question, and the following aul his experiments 
with their results > 
“Ist. I boiled during four hours, in five poe four and 
a half ounces of. hydrated peroxide of iron, taken from different — 
apothecaries, with four ounces of distilled water, and by Marsh’s 
Ppeptatus no trace of arsenic could be obtained. 
“2d. I then added thirty grains of pure caustic potash to the 
hydrated peroxide of iron in each capsule, but no trace of arsenic 
could be obtained. 
“3d, But on treating by an ebullition of five hours an equal 
quantity of hydrated peroxide of iron in pure sulphuric acid, the 
liquid of three capsules out of the five gave arsenical taches. 
“4th. Four portions of four ounces each of colcothar of com- 
merce, (the anhydrous peroxide of iron formed by heating the 
sulphate,) obtained from different merchants, by ebullition for 
four hours in distilled water, did not give indications of the pres- 
ence of arsenic. 
“5th. This substance in the same quantity by ebullition du- 
ting five hours with strong sulphuric acid, gave large arsenical 
taches with the aid of Marsh’s apparatus. 
