108  Scanimony  Resin.  {Ai^mSS^n^' 
night,  then  filtering  through  a  tared  filter,  washing  filter  and  residue 
carefully  with  ether,  drying  at  ioo°  .  C,  and  weighing  filter  and 
residue.  In  this  connection  we  may  mention  the  process  for  the 
rapid  determination  of  resin  in  scammony  as  published  by  E. 
Dowzard  {Pharm.  Jour.  (4),  18,  469),  in  which  he  digests  a  weighed 
amount  of  drug  or  gum-resin  scammony  with  ether,  filters  the 
ethereal  solution  through  a  dried  filter  and  determines  the  resin  by 
evaporating  to  dryness  in  a  tared  vessel  an  aliquot  portion  of  this 
ethereal  solution.  This  method  differs  from  the  one  used  by  Cowie 
in  the  use  of  an  aliquot  part  of  the  ethereal  solution  instead  of  the 
entire  solution,  thus  being  much  more  rapid.  A  correction  is  given 
for  the  increase  in  volume  of  the  ether  by  reason  of  the  dissolved 
resin.  The  chief  objection  to  this  method  is  that  the  solvent  is  so 
extremely  volatile  that  in  filtering  and  measuring  off  the  aliquot 
part,  however  rapidly  this  may  be  done,  some  loss  must  occur  by 
reason  of  evaporation,  rendering  the  solution  therefore  more  con- 
centrated. The  method  will  undoubtedly  work  rapidly  and  for 
ordinary  purposes  will  probably  be  sufficiently  accurate.  Whenever 
possible,  it  is  therefore  by  all  means  preferable  to  use  the  method 
which  we  have  suggested  or  the  usual  one  of  extraction  by  means 
of  a  Sohxlet  apparatus.  As  was  to  be  expected  in  a  resin  yielding 
so  little  ash,  the  ether  solubility  was  correspondingly  high.  The 
conclusion  is  not  to  be  drawn  from  this  that  low  ash  and  high  ether 
solubility  are  always  to  be  found  together  in  proportional  percent- 
ages, but  merely  that  from  a  resin  containing  but  a  trace  of  inorganic 
matter  there  has  been  removed  a  large  portion  of  the  matter  which 
is  ordinarily  insoluble  in  ether.  The  sample  of  scammony  resin 
(number  9)  is  the  least  soluble  but  still  attains  the  high  percentage 
of  96.5  ether-soluble  resin.  This  is  at  variance  with  the  results  of 
Cowie  and  Brander,  but  agrees  with  those  of  some  other  observers. 
Acid  Value. — In  the  determination  of  the  acid  value  the  usual 
process  for  oils  was  followed,  and,  as  was  expected,  considerable 
difficulty  was  experienced  in  determining  the  end  point  of  the  titra- 
tion because  of  the  dark  colored  solution.  This  difficulty  was  still 
further  enhanced  by  the  fact  that  the  resin  solution  darkened  very 
considerably  on  addition  of  alkali  until  it  was  with  great  difficulty 
that  the  final  change  in  color  of  the  indicator  was  observed.  For 
the  determination  2  grammes  of  resin  were  dissolved  in  a  mixture 
of  50  c.c.  each  of  alcohol  and  acetone.  This  was  titrated  at  first 
with  N/5  alcoholic  soda,  but  it  was  found  that  the  solution  became 
