252  Retention  of  Arsenic.  {AmjineMSfrm^ 
Medical  School,  Washington,  D.  C,  in  which  Mr.  Noyes  found  that 
a  very  considerable  amount  of  arsenic  had  been  retained  by  the  ani- 
mal charcoal.  The  matter  was  of  such  interest  to  us  that  we  under- 
took the  confirming  of  Mr.  Noyes'  observations.  Our  results,  as 
detailed  below,  confirm  Mr.  Noyes'  observations. 
EXPERIMENT  NO.  I. 
A  quantity  of  animal  charcoal  weighing  789-4  grammes  was  dried 
at  110°  C.  to  constant  weight.  The  constant  weight,  was  777-88$ 
grammes,  showing  a  loss  of  11-515  grammes,  or  1-458  per  cent,  in 
weight. 
0-4455  gramme  arsenious  oxide  was  dissolved  in  3,000  c.c.  of  dis- 
tilled water  and  the  solution  was  passed  through  the  animal  charcoal. 
The  time  required  for  the  passage  of  the  solution,  i  e.y  until  liquid 
ceased  to  come  from  the  charcoal,  was  three  hours.  Of  the  3,000  c.c. 
of  solution,  2,670  c.c.  passed  through,  leaving  330  c.c.  as  the  volume 
retained  in  the  mass  of  charcoal. 
Of  the  liquid  which  had  passed  through,  100  c.c.  were  taken, 
sulphurous  acid  added  to  reduce  any  arsenic  acid  which  may  have 
been  produced,  the  sulphurous  acid  expelled  by  heat,  the  liquid 
strongly  acidulated  with  hydrochloric  acid  and  a  slow  stream  of 
washed  hydrogen  sulphide  conducted  into  the  warmed  liquid  for 
several  hours  and  then  stood  aside  in  a  warm  place  over  night.  The 
arsenious  sulphide  was  collected  .on  a  previously  washed  and  dried 
filter,  washed  with  boiled  water,  then  with  alcohol,  with  ether,  and 
finally  with  carbon  disulphide,  and  then  dried  and  weighed. 
Two  determinations,  using  100  c.c.  of  the  liquid  in  each  case,  were 
made. 
a  yielded  0-0069  gramme  arsenious  sulphide. 
b      "   0-0063       "  "  " 
The  mean  of  the  two  determinations  is  0-0066  gramme,  which 
corresponds  to  0-0053  gramme  of  arsenious  oxide.  Each  100  c.c. 
of  the  original  solution  of  arsenious  oxide  before  it  was  passed 
through  the  charcoal  contained  0-01485  gramme  arsenious  oxide; 
therefore,  the  amount  of  arsenious  oxide  retained  by  the  animal 
charcoal  from  each  100  c.c.  was  0-00955  gramme,  or  64  30  per  cent. 
This  is  assuming  that  the  330  c.c.  of  liquid  which  remained  in  the 
animal  charcoal  as  liquid  held  mechanically  to  saturate  the  mass  of 
charcoal,  contained  proportionately  the  same  percentage  of  arsenious 
