ABSORPTION OF SALINE SUBSTANCES BY CHARCOAL. 145 
I next proceeded to ascertain the quantity of arsenious 
acid which animal charcoal is capable of absorbing. Prof. 
Graham had asserted that no absorption occurs ; Dr. Gar- 
rod states, on the contrary, that it is so perfect and quick, 
that he did not fear to recommend charcoal powder as a far 
better antidote to arsenic than the hydrated sesquioxide of 
iron. I adopted the following plan for testing the correct- 
ness of these assertions. After having found that, even on 
employing considerable quantities of charcoal, arsenious 
acid was constantly detected in the filtered liquid, 1 endea- 
vored to ascertain whether any had been absorbed. For 
this purpose I dissolved 10 grms. of arsenious acid in a litre 
of distilled water; I then took 10 cub. centim. of this solu- 
tion, to which I added 10 cub. centim. C1H, with 100 cub. 
centim. distilled water, and which served to determine the 
strength of a solution of permanganate of potash, intended 
for estimating the arsenic according to M. Bussy's process. 
Having determined the strength of the normal solution, I 
poured 100 cub. centim. of the solution of arsenious acid 
over different quantities of charcoal ; and when the filtra- 
tion was finished, I washed the charcoal with a little dis- 
tilled water, so as to re-obtain 100 cub. centim. Of this I 
took the first time 10 cub. centim., and added to them 5 
cub. centim. C1H and 100 cub. centim. distilled water. I 
then added with precaution the permanganate of potash. — 
The following results were obtained with blood charcoal: — 
10 grms. of charcoal absorbed 0-2 AsO 3 
20 ... 0-3 .. . 
40 ... 0-4 .. . 
Upon boiling the arsenical solution with the charcoal, the 
results were somewhat different : 
10 grms. of charcoal absorbed 0-3 AsO* 
20 ... 0-5 .. . 
40 ... 0-7 .. . 
A still more difficult question remained to be solved — 
How does the charcoal act under these circumstances ? Is 
13 
