Am'jJa°nri884arm'}        Vesicating  Principle  of  Croton  Oil  25 
when  applied  to  the  skin.    It  has  an  acid  reaction  and  a  sp.  gr.  of  *987. 
Solvents  were  first  tried  as  a  means  of  further  separation.  Water, 
alcohol  of  various  strengths,  benzol,  chloroform,  ether,  petroleum 
naphtha,  etc.,  were  tried,  at  different  temperatures  and  in  various  pro- 
portions, but  the  results  did  not  indicate  a  method  of  further  separation. 
The  oil  was  then  subjected  to  distillation,  alone,  with  acids,  alkalies, 
and  by  the  passage  through  it  of  heated  steam.  Several  distillates 
were  thus  obtained,  but  they  were  all  non-vesicating.  The  oil  there- 
fore contains  no  free  volatile  vesicating  principle,  neither  does  the 
vesicating  activity  exist  in  a  combined  volatile  alkaloid  or  alcohol. 
To  determine  whether  the  fatty  acids  or  alcoholic  radical  contained 
the  vesicating  principle,  the  oil  was  subjected  to  saponification,  first  of 
the  free  fatty  acids.  50  grams  of  oil  were  digested  on  a  water-bath 
for  one  hour,  with  12J  grams  of  sodium  bicarbonate  and  10  grams  of 
water.  The  resulting  soapy  mass  was  agitated  with  petroleum  naphtha, 
and  the  whole  placed  on  a  filter  and  repeatedly  washed  with  the  same 
solvent.  The  filtrate  containing  the  unsaponified  neutral  oil,  when 
evaporated  and  dried,  weighed  38'7  grams;  the  difference,  representing 
free  fatty  acids,  being  11*3  grams  or  22  J  per  cent,  of  the  alcohol-soluble 
oil.  The  soap  left  on  the  filter  was  diffused  in  hot  water  and  decom- 
posed with  sulphuric  acid.  The  free  fatty  acids  which  separated  in 
white  flocculi  were  collected  and  washed,  dissolved  in  alcohol  and  crys- 
tallized. In  this  state  their  melting  point  indicated  fairly  pure  palmitic 
acid,  which  was  devoid  of  any  vesicating  property.  The  vesicating 
activity  does  not,  therefore,  reside  in  the  free  fatty  acids. 
Returning  now  to  the  neutral  oil,  this  was  saponified  by  10  grams 
of  caustic  soda  and  20  grams  of  water.  The  soap  on  cooling  rose  to 
the  top  as  a  hard  cake,  from  which  the  aqueous  solution  containing  the 
alcohol  radical  was  easily  separated.  This  on  concentration  gave  no 
evidence  of  containing  any  vesicating  principle.  The  soap  was  dif- 
fused in  hot  water,  decomposed  with  sulphuric  acid,  and  the  free  fatty 
acids  separated.  The  soap  previous  to  decomposition  had  no  tendency 
to  vesicate,  but  the  free  acids  when  liberated  were  strongly  vesicant. 
It  was  now  evident  that  the  vesicating  principle  was  among  the  fatty 
acids ;  the  next  experiments  were  directed,  therefore,  to  their  separation. 
This  has  at  present  been  accomplished  only  in  an  approximate  manner, 
but  the  subject  presented  so  many  difficulties  that  it  seemed  advisable 
to  publish  the  results  so  far  obtained. 
Many  processes  were  applied  to  the  separation  of  these  acids,  which 
