'  }     Chemical  Examination  of  Ipomcea  Purpurea.  253 
.r etroieuin  ^o.  p.  40-00  v^.j 
extracted. 
017  gramme    —    u  34  per  cent. 
Ether  
0*30       "           =  o*6o  "  (f 
0-34       "          =  o'68  (t  " 
<  < 
3*07   grammes  =    6*14  "  " 
Water   . 
5*25       "         =  10*50  " 
Total 
9-13       "            18-26   "  " 
Determination  of  Total  Resin. 
For  the  determination  of  the  total  resin  in  the  drug  the  following 
method  was  employed  : — Fifty  grammes  of  the  finely-ground  material 
were  thoroughly  extracted  in  a  Soxhlet  apparatus  with  hot  alcohol 
(94  per  cent).  To  the  liquid  thus  obtained  25  c.c.  of  water  were 
added,  and  the  alcohol  removed  by  distillation,  after  which  the  resi- 
due was  brought  into  a  dish  and  heated  on  a  water-bath  in  order  to 
remove  the  last  traces  of  alcohol.  The  separated  resin  was  then 
washed  three  or  four  times  with  hot  distilled  water,  and  finally  dried 
in  a  water-oven  until  of  constant  weight.  Two  concurrent  deter- 
minations yielded  2-4  grammes  of  resin,  corresponding  to  4-8  per 
cent,  of  total  resin  in  the  drug.  The  proportion  of  this  crude  resin 
which  was  soluble  in  ether,  as  determined  by  its  complete  extrac- 
tion with  the  latter  solvent  in  a  Soxhlet  apparatus,  corresponded 
to  15-5  per  cent,  of  its  weight. 
Optical  Rotation  of  the  Crude  Resin. 
It  has  been  indicated  by  P.  Guigues1  that  the  specific  optical  rota- 
tory power  of  certain  convolvulaceous  resins  is  a  factor  which  may  be 
utilized  for  discriminating  between  them,  and  for  the  detection  of 
substitutes  and  adulterants.  Thus  the  resin  of  scammony,  obtained 
from  the  root,  is  said  to  have  a  rotation  varying  from  —  180  30'  to 
— -2 3°  30',  whereas  the  upper  limit  for  the  resin  from  the  natural 
gum-resin  scammony  is  —  25 °.  Resins  having  a  rotation  between 
—  23 0  30'  and  — 25°  are  considered  to  be  derived  from  Ipomcea 
orizabensis,  Ledanois/  The  addition  to  the  above  products  of  offi- 
cial jalap  resin  or  that  of  Ipomoea  turpethum,  R.Br.,  increases  the 
rotation,  while  an  admixture  of  colophony,  sandarac  or  mastic  would 
lower  it,  since  the  latter  are  dextrorotatory. 
1  Jo  urn.  de  Pharm.  et  de  Chim.  [6J,  33,  241,  and  Chem.  Centralblatt,  1907, 
Bd.  I,  p.  309. 
