*\^ptember?i9io!"}     Scammony  and  Resin  Scammony,  431 
about  100  c.c.  of  neutral  alcohol,  and  the  titration  made  with  one-half 
normal  alcoholic  potash  and-  phenolphthalein.  The  solution  of  the 
resin  is  thus  brought  against  a  white  background,  in  a  thin  layer, 
which  facilitates  the  determination  of  the  end  point.  Even  with 
this  aid,  however,  the  determination  is  not  always  satisfactory,  and 
little  confidence  can  be  placed  in  the  accuracy  of  the  results.  An 
attempt  to  use  ^  barium  hydrate  solution  was  unsuccessful,  since 
the  color  developed,  if  anything,  was  darker  than  that  caused  by 
the  potassium  hydroxide. 
The  saponification  values  were  determined  in  the  usual  way, 
using  N  caustic  potash. 
Ether  solubilities  were  determined  in  both  commercial  and  an- 
hydrous ether.  The  commercial  ether  had  a  sp.  gr.  of  .7128  at  25  °, 
while  the  anhydrous  ether  had  a  sp.  gr.  of  .7106.  It  will  be  noted, 
as  Cowie  has  already  pointed  out,,  that  the  ether  solubility  varies 
with  the  nature  of  the  ether  used. 
A  rather  extended  study  of  the  iodine  numbers  was  made.  The 
method  by  Htibl  was  applied  at  first,  but  it  was  found  to  be  im- 
possible to  obtain  concordant  results  by  it.  The  iodine  numbers 
varied  in  some  cases  100  per  cent,  when  the  different  tests  were 
allowed  to  stand  for  different  lengths  of  time.  Moreover,  no  definite 
end-point  could  be  found  when  titrating  the  excess  of  iodine  with 
sodium  thiosulphate  and  starch  indicator.  The  solution  continually 
became  blue  within  ten  seconds  after  being  decolorized,  and  this 
often  continued  during  the  addition  of  3  to  5  c.c.  of  thiosulphate 
solution.  This  method  was  finally  given  up  and  the  determinations 
were  made  according  to  the  method  of  Wijs.1  This  method  has 
proven  itself  to  be  so  satisfactory  that  we  can  recommend  it  most 
highly,  at  least  when  working  with  these  resins.  The  solution  is 
prepared  as  follows  :  9  Gms.  of  powdered  iodine  are  dissolved  by 
the  aid  of  heat  in  500  c.c.  of  glacial  acetic  acid.  Chlorine  gas, 
washed  through  water,  and  dried  by  sulphuric  acid,  is  then  passed 
into  the  solution,  using  a  capillary  tube  to  insure  more  complete 
absorption.  Thus  the  iodine  is  converted  into  iodine  monochloride. 
The  completion  of  the  reaction  is  shown  by  the  sudden  disappearance 
of  the  dark-brown  color  of  the  solution,  and  this  end-point  is  very 
1  Berichte,  31;  750  (i8g8)  ;  Chem.  Rev.  Fett-u.  Harz-Ind.  6;  5;  see  also 
the  excellent  article  by  Harvey,  Journ.  Soc.  Chem.  Ind.  21 ;  No.  23,  1437 
(1902). 
