As™ptemberPi9io!'}     Scammony  and  Resin  Scammony.  435 
as  a  varnish  on  the  walls  of  the  vessel.  This  does  not  take  place 
with  resin  made  from  scaramony  or  from  scammony  root,  and  this 
appearance  can  be  used  to  detect  Mexican  scammony  in  the  presence 
of  a  considerable  quantity  of  true  scammony  resin.  Using  anhy- 
drous ether,  the  insoluble  portion  assumes  a  granular  form,  which 
on  standing  settles  to  the  bottom  as  a  sticky  mass. 
The  portion  insoluble  in  chloroform  was  generally  gelatinous 
and  rather  dark  in  color. 
We  have  already  spoken  of  the  difficulty  encountered  in  deter- 
mining the  iodine  numbers  by  the  method  of  Hiibl.  For  example, 
sample  II  after  being  allowed  to  stand  for  four  hours  gave  an 
iodine  number  of  5.5;  after  standing  for  fifteen  hours  this  value 
had  risen  to  8.8;  and  another  test  which  was  allowed  to  stand  for 
twenty-four  hours  showed  only  8.22.  Sample  V  with  Hubl's  method 
gave  8.38  after  five  hours  and  10.58  after  fifteen  hours,  while  the 
same  resin  by  Wijs's  method  gave  11.6  in  one  hour.  The  average 
of  our  iodine  values  is  slightly  greater  than  the  average  of  Taylor's. 
As  can  be  seen  from  the  tables,  no  definite  relation  exists  between 
the  variety  of  resin  and  the  iodine  value,  and  this  method  cannot  be 
used  as  a  means  of  differentiating  the  resins.  We  wish,  again, 
however,  strongly  to  recommend  the  method  of  Wijs.  It  is  con- 
venient, rapid,  and  accurate,  duplicate  determinations  agree  well, 
the  end-point  is  sharp,  and  work  is  considerably  lessened  by  the 
fact  that  the  solution  is  stable  and  blanks  are  unnecessary  for  each 
determination.  The  solution  should  be  kept  in  a  dark  bottle,  other- 
wise the  acetic  acid  is  likely  to  be  substituted  by  the  halogens 
and  the  solution  will  lose  in  strength. 
The  specific  rotations  also  fall  into  two  distinct  groups.  The 
values  found  for  the  resins  known  to  be  derived  from  Convolvulus 
scammonia  are  close  to  — 240,  while  those  for  the  Mexican  resins 
are  all  over  — 31  °.  Guigues,  as  mentioned  before,  was  the  first  to 
call  attention  to  this  fact.  Our  value  of  — 25.980  for  sample  I  is 
slightly  higher  than  his  maximum  of  — 24. 5  0  obtained  for  a  specimen 
prepared  in  an  identical  manner,  and  our  value  of  — 24.240  for 
sample  III  is  slightly  higher  than  his  limit  of  — 23. 5 0  for  resin 
extracted  from  the  true  root.  These  determinations  can  be  made 
with  a  considerable  degree  of  accuracy,  and  the  optical  rotations 
furnish  a  valuable  means  of  distinguishing  the  true  and  false  resins. 
The  specific  rotation  of  the  Mexican  resin  approaches  the  specific 
rotation  of  resin  jalap,  but  the  high  price  of  resin  jalap  would  pre- 
vent any  adulteration  of  Mexican  resin  with  the  former. 
