Am'ieSt:,fm!m'}        Preparation  of  Oak  Tannins.  435 
THE  PREPARATION  OF  THE  OAK  TANNINS,  WITH 
SPECIAL  REFERENCE  TO  THE  USE  OF 
ACETONE  AS  A  SOLVENT.1 
By  Henry  Trimble  and  Josiah  C.  Peacock. 
The  usual  method  for  preparing  a  tannin  from  a  substance  as  rich 
as  nutgalls,  or  containing  from  60  to  70  per  cent,  of  the  astringent 
principle,  is  to  extract  with  a  mixture  of  alcohol  and  ether,  or,  what 
amounts  to  the  same  thing,  official  ether,  sp.  gr.  0750.  When, 
however,  the  material  is  an  oak  bark,  containing  from  4  to  15  per 
cent,  of  tannin,  the  choice  of  a  proper  solvent  becomes  a  more 
difficult  matter. 
During  the  past  year  a  number  of  experiments  have  been  made 
on  oak  bark  with  a  view  of  determining  the  most  satisfactory  solvent 
for  the  tannin.  The  following  are  especially  worthy  of  considera- 
tion : 
(1)  Official  ether  sp.  gr.  0750,  which  is  equivalent  to  a  mixture 
of  alcohol  and  ether. 
(2)  Acetic  ether. 
(3)  Water. 
(4)  Acetone. 
The  greatest  objections  to  ether  are  its  expense  and  the  slowness 
of  its  solvent  action,  which  consume  time  as  well  as  a  large  amount 
of  menstruum. 
Acetic  ether  is  a  much  better  solvent,  and  the  expense  is  the 
chief  difficulty  in  the  way  of  its  use. 
Water  is  slow  in  its  solvent  action  ;  this,  however,  is  in  part  over- 
come by  long  maceration,  and  then  slow  percolation.  The  tannin 
must  be  separated  from  the  resulting  aqueous  solution,  either  by 
agitation  with  acetic  ether,  or  by  precipitation  with  lead  acetate. 
In  the  latter  process  it  was  found  possible  at  a  considerable  sacrifice 
of  oak  bark  to  procure  a  quantity  of  light-colored  tannin,  by  pre- 
cipitating one-half  of  the  aqueous  percolate  with  lead  acetate,  col- 
lecting the  precipitate,  stirring  it  through  the  other  half  of  the 
percolate,  and  then  filtering.  The  filtrate  was  very  light  in  color^ 
and  was  either  evaporated  under  reduced  pressure  and  submitted  to 
further  purification  to  be  described  hereafter,  or  it  was  agitated  with 
1  Read  at  the  meeting  of  the  American  Pharmaceutical  Association,  Aug.  16. 
