328 
ON POISONING BY ARSENIOUS ACID. 
arsenite of lime, which hence remains in the part where it 
was accidentally deposited, and is not dispersed throughout 
the neighboring parts. MM. Flandin and Danger might 
then have been unable to find arsenic in one portion of the 
soil, without being able to say that it does not exist in portions 
not examined by them. 
Examining the question of the spots produced by MM. 
Flandin and Danger. According to these gentlemen, on 
introducing into Marsh's apparatus, while in operation, the 
sulphite and phosphite of ammonia, still more Dippel's animal 
oil or oil turpentine, spots may be procured similar to the 
arsenical deposits, and which afford all the reactions of 
arsenious acid. M. Orfila stated that he had prepared with 
30 centigrammes of sulphite of ammonia, a like quantity of 
phosphite and 18 drops of oil of turpentine, spots, equal to 
those procured by MM. Flandin and Danger*; and which he 
presents to the Academy, together with some produced by 
arsenic. The difference between these deposits are so striking 
that he can scarcely suppose it possible to mistake the one for 
the other. In fact the former are large, brown with a varied 
reflection of yellow, very brilliant; it is very easy to dis- 
tinguish them with the naked eye, so little do they possess 
any similarity to the brown arsenical spots. They promptly 
redden moistened litmus paper, even when recent, while the 
arsenical spots, even when old do not change this paper, at 
least if not procured by a strong flame and a portion of 
sulphuric acid has not been projected from the apparatus. 
To perform this experiment, the moistened paper should be 
applied upon the spot and then pressed with a glass rod, 
and not with the finger, for this constantly reddens the test 
paper. 
Strong nitric acid neither dissolves nor detaches entirely, 
ivhen cold, the spots produced by MM. Flandin and Danger 
even when assisted by the action of a glass tube. At the 
boiling temperature, they slowly dissolve, and produce a 
yellow liquid. If this liquid be evaporated to dryness there 
remains a residue of yellow, bordering slightly on a brown 
