26  Vesicating  Principle  of  Croton  Oil.        | Am  Va^iS arm' 
after  much  time  and  careful  working  gave  only  negative  results.  The 
description  of  these  I  shall  omit.  The  following  gave  the  only  results 
from  which  even  general  conclusions  could  be  drawn : — First,  separa- 
tion by  means  of  the  different  congealing  points  of  the  glycerides  of 
the  fatty  acids.  Second,  separation  by  means  of  the  different  solubili- 
ties of  their  lead  salts  in  alcohol  and  ether.  Third,  separation  by 
fractional  saponification.  Fourth,  separation  by  fractional  decomposi- 
tion of  the  soda  salts.  The  first  of  these  separations  was  accomplished 
by  filtration  and  slight  pressure  through  a  plug  of  tow  in  a  jacketed 
funnel  surrounded  by  refrigerating  mixtures.  The  manner  of  accom- 
plishing the  other  three  separations  does  not  require  a  special  descrip- 
tion. 
The  conclusions  from  the  results  of  these  processes  were  briefly  as 
follows: — First,  the  vesicating  principle  is  contained  in  those  acids 
having  the  lowest  melting  points.  Second,  the  lead  salt  is  soluble  in 
ether,  but  not  at  all,  or  very  slightly,  in  alcohol.  Third,  it  is  contained 
in  those  acids  least  readily  saponified  by  alkalies.  Fourth,  it  is  con- 
tained in  those  acids  first  liberated  when  the  alkali  soap  is  decomposed 
by  acids. 
In  the  next  experiment  the  acids  were  separated  into  four  groups, 
as  follows: — First,  those  having  ammonia  salts  insoluble  in  alcohol 
(palmitic  ..acid).  Second,  those  (after  removal  of  group  1)  which  are 
precipitated  from  alcoholic  solution  by  magnesium  acetate.  Third, 
those  which,  in  the  absence  of  groups  1  and  2,  are  precipitated  as 
insoluble  barium  salts  in  alcoholic  solution  (oleic,  etc.).  Fourth,  those 
whose  barium  salts  are  soluble  in  alcohol.  The  fatty  acids  were  dis- 
solved in  alcohol  and  saturated  solutions  of  the  reagents  were  added. 
The  precipitate  in  each  case  was  washed  on  a  filter  with  cold  alcohol. 
The  yield  of  acids  in  each  group  was,  in  round  numbers,  group  1,  15 
per  cent.;  group  2,  20  per  cent.;  group  3,  40  per  cent.,  and  group  4, 
25  per  cent,  of  total  fatty  acids  in  the  neutral  alcohol-soluble  croton 
oil.  The  acids  of  groups  1,  2  and  3  were  entirely  inactive  as  regards 
vesicating  effects,  but  those  separated  in  group  4  were  highly  vesicant. 
These  acids  when  separated  are  of  a  dark  brown  color,  and  remain 
liquid  at  50°F.  They  may  be  further  purified  b)^  saponification  with 
plumbic  oxide,  solution  of  the  soap  in  ether  and  regeneration  with  an 
acid.  In  this  state  they  are  rendered  much  more  active.  Taking  into 
consideration  the  low  melting  point  and  the  solubilities  of  the  metalic 
salts,  together  with  the  results  of  the  experiments  on  the  separation  of 
