THE  AMERICAN 
JOURNAL  OF  PHARMACY 
JUNE,  1903. 
THE  RETENTION  OF  ARSENIC  BY  ANIMAL  CHARCOAL. 
By  John  Marshall, 
Professor  of  Chemistry  and  Toxicology,  University  of  Pennsylvania. 
AND 
Leon  A.  Ryan, 
Assistant  Demonstrator  of  Chemistry,  University  of  Pennsylvania. 
At  a  recent  meeting  of  the  Philadelphia  Section  of  the  American 
Chemical  Society,  the  inventor  of  a  water  filter  in  which  animal 
charcoal  is  employed  read  a  paper  in  which  the  statement  was 
made  that  when  aqueous  solutions  of  the  salts  of  some  of  the  metals 
were  passed  through  animal  charcoal,  the  latter  removed  the  metals 
from  the  solution,  and  that  even  arsenic  in  aqueous  solution,  as 
arsenious  acid,  could  in  large  part  be  removed. 
The  retention  in  the  mass  of  charcoal  of  those  metals  which  form 
insoluble  phosphates  is  what  one  would  expect  because  of  the  for- 
mation of  such  phosphates  by  the  soluble  phosphates  of  the  animal 
charcoal  and  their  mechanical  retention  in  the  mass  of  charcoal,  but 
this  explanation  would  not  apply  to  arsenic. 
On  passing  distilled  water  through  animal  charcoal,  we  found  that 
on  adding  plumbic  acetate  to  a  portion  of  the  liquid  that  had  been 
passed  through,  a  copious  precipitate  of  plumbic  phosphate  was  pro- 
duced; but  on  adding  a  solution  of  arsenious  acid  to  another  portion 
of  the  liquid,  no  evidence  of  any  change  whatever  was  observed. 
The  reader  of  the  paper  quoted  some  unpublished  investigations 
on  the  retention  of  animal  charcoal,  made  by  Mr.  Edward  R.  Noyes, 
under  the  direction  of  C.  H.  White,  M.D.,  Medical  Director  U.  S.  N. 
(now  retired),  in  the  United  States  Naval  Museum  of  Hygiene  and 
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