210 
Current  Literature. 
(Am.  Jour.  Pharm. 
V     March,  1918. 
The  use  of  this  earth  for  the  isolation  of  alkaloids  from  plant  ex- 
tracts and  for  the  separation  of  "  vitamines  "  has  already  been  re- 
ported and  has  claimed  the  attention  of  several  investigators. 
The  present  communication  deals  with  the  relative  adsorptive 
power  of  various  fuller's  earths,  the  effect  of  time  on  the  rate  of 
adsorption,  etc.  Experiments  with  solutions  of  methylene  blue  and 
of  quinine  bisulphate  show  that  only  the  free  base  is  adsorbed  when 
these  solutions  are  placed  in  contact  with  fuller's  earth  and  that 
when  both  of  these  chemicals  are  present  in  the  solution  there  is  a 
simultaneous  adsorption.  Experiments  were  also  carried  on  to 
determine  the  effect  of  ethyl  alcohol  ^nd  of  cane  sugar  on  such  ad- 
sorptive. 
The  following  is  the  summary  of  the  conclusions : 
A  comparison  of  the  adsorptive  capacities  of  36  samples  of 
fuller's  earths  and  other  clays  showed  that  English  earth  is  superior 
to  any  of  the  domestic  fuller's  earths  except  one,  the  exact  source 
of  which  could  not  be  learned.  Domestic  bentonite  exhibits  a  higher 
adsorptive  power  than  the  English  samples  of  fuller's  earth,  but  on 
account  of  its  exceptional  capacity  for  retaining  water,  it  cannot  be 
used  to  advantage  in  cases,  such  as  the  present,  where  a  sharp 
separation  of  solid  and  solution  is  essential. 
It  was  found  that  the  adsorption  of  quinine  bisulphate  and 
methylene  blue  by  fuller's  earth  increased  with  time  of  contact  but 
at  a  gradually  diminishing  rate.  It  was  also  found  that  the  amounts 
adsorbed  continued  to  increase  with  amount  of  -excess  present. 
Maxima  were  not  observed  in  the  case  of  either  the  time  factor  or 
the  concentration  factor. 
In  the  case  of  both  quinine  bisulphate  and  of  methylene  blue  the 
free  base  only  is  adsorbed  from  the  aqueous  solution  when  brought 
in  contact  with  fuller's  earth.  The  acid  component  of  each  com- 
pound unites  with  calcium  derived  from  the  fuller's  earth  and  re- 
mains in  the  aqueous  solution. 
When  equal  amounts  of  quinine  bisulphate  and  methylene  blue 
are  simultaneously  present  in  an  aqueous  solution  shaken  with 
fuller's  earth,  both  compounds  are  adsorbed  to  approximately  -the 
same  extent.  The  sum  of  the  two  components  is  about  25  per  cent, 
greater  than  the  amount  of  either  adsorbed  separately. 
When  the  same  portion  of  fuller's  earth  is  first  shaken  with 
methylene  blue  and  then  with  quinine  bisulphate,  a  small  amount  of 
the  latter  compound  is  taken  up  and  only  a  trace  of  the  former 
