436 
Preparation  of  Oak  Tannins. 
Am.  Jour.  Pharru. 
Sept.,  1893. 
acetic  ether,  and,  after  removal  of  the  latter  solvent,  purified  in  the 
same  manner. 
Apart  from  the  slowness  of  this  process,  the  yield  of  tannin  after 
purification  was  always  small  when  water  was  used  as  a  solvent. 
Within  the  past  few  years  acetone  has  appeared  in  commerce  in 
a  nearly  pure  form.  Its  solvent  action  has  been  suggested  for 
several  plant  principles,  but  thus  far  little,  if  any,  reference  has  been 
made  to  its  use  as  a  solvent  for  tannin,  although  there  is  good 
reason  for  believing  that  some  manufacturers  are  using  it  for  the 
extraction  of  nutgalls.  It  is  cheaper  than  ether,  but  more  expen- 
sive than  alcohol.  It  is  a  better  solvent  of  tannin  than  either  of 
these,  and  extracts  the  tannin  with  less  sugar  and  other  carbo- 
hydrates, because  of  its  poor  solvent  power  over  these.  Its  low 
boiling  point,  56  5 °,  renders  its  recovery  easy  and  rapid,  without 
danger  of  decomposition  to  the  tannin. 
From  a  sample  of  powdered  nutgalls,  commercial  ether  extracted 
5977  Per  cent,  of  solids,  while  acetone  extracted  62-24  per  cent,  of 
the  same. 
The  following  process,  after  some  preliminary  experiments,  has 
been  devised  and  thus  far  proven  satisfactory. 
The  powdered  oak  bark  was  well  moistened  with  acetone,  packed 
in  a  glass  percolator,  and  the  menstruum  poured  on  until  it  com- 
menced to  drop  from  the  lower  orifice,  when  the  latter  was  closed 
with  a  cork  and  the  bark  allowed  to  macerate  for  forty-eight  hours. 
Enough  of  the  solvent  was  poured  on  before  maceration  com- 
menced to  keep  a  thin  layer  of  it  above  the  drug.  A  glass  plate 
smeared  with  petrolatum  was  kept  on  top  the  percolator  to  prevent 
evaporation.  At  the  expiration  of  the  maceration  period,  the 
stopper  was  removed  and  the  percolation  continued  rapidly  until 
the  number  of  litres  of  percolate  amounted  to  one-half  the  number 
of  kilograms  of  oak  bark  used.  The  latter  was  then  usually  found 
to  have  been  exhausted.  In  some  instances,  a  No.  20,  in  others 
a  No.  40  powder  was  used.  In  every  case  the  acetone  rapidly 
penetrated  the  drug  and  accomplished  complete  exhaustion. 
The  acetone  was  removed  by  distillation,  the  first  portion  on  a 
water-bath,  under  ordinary  conditions,  but  the  last  portions  by  the 
additional  aid  of  reduced  pressure.  The  residual  product  was  a 
dark  red  or  brown  semi-solid  extract.  This  was  warmed  with  water 
until  nearly  all  of  it  dissolved.    After  cooling,  the  whole  was  fil— 
