DETECTION  OP  CROTON  OIL  IN  MIXTURES. 
30T 
cumstances,  and  the  question  would  then  occur,  how  are  we  to 
prove  the  presence  of  croton  oil?  We  can  readily  prove  the 
absence  of  sulphur,  but  this  would  not  prove  whether  or 
not  croton  oil  was  contained  therein,  unless  we  were  by  distilla- 
tion to  remove  all  volatile  matter  from  this  mixture.  Small 
quantities  cannot  be  well  analysed  in  this  way,  as  the  inflamma- 
tion produced  might  be  too  slight ;  besides,  this  method  would 
not  be  one  easily  executed. 
In  searching  for  a  convenient  and  ready  mode  for  proving  in 
oily  mixtures  the  presence  of  croton  oil,  I  availed  myself  of  the 
results  of  Dr.  Thomas  Schlippe's  researches  on  croton  oil, 
(Annalen  d.  Chem.  und  Pharm.  cv.)  who,  without  being  able  to 
discover  the  cathartic  principle,  found  the  rubefacient  ingredi- 
ent, crotonol,  to  be  a  resinous  principle,  which,  together  with 
other  resins  and  free  acids,  is  removed  from  the  oil,  by  agitation 
with  an  alcoholic  solution  of  caustic  soda,  and  then  separated 
by  neutralizing  the  solution  with  hydrochloric  acid.  This 
mixture  of  various  components  of  croton  oil,  possesses  the 
property  of  reddening  the  skin  in  a  high  degree. 
I  have  followed  strictly  these  directions,  sometimes  substi- 
tuting for  the  soda,  caustic  potassa,  and  sulphuric  for  hydrochloric 
acid,  with  the  same  good  results.  Experimenting,  first  with 
mixed  oils,  containing  from  J  to  ^  of  croton  oil,  I  afterwards 
operated  with  olive  and  almond  oil,  containing  one  drop  to  the 
ounce.  The  quantity  of  caustic  potassa  is  regulated  according 
to  the  amount  of  croton  oil,  or,  if  unknown,  in  accordance  with 
the  effect  of  the  oil  upon  the  skin.  For  oils  insoluble  in  alcohol, 
I  have  used  85  per  ct.  alcohol,  adding  to  it  a  sufficient  amount 
of  an  alcoholic  solution  of  caustic  potassa,  and  agitating  well ; 
after  separation  had  taken  place,  I  removed  the  alcoholic  liquid, 
and  added  to  it  an  equal  amount  of  water,  and  a  sufficient  quantity 
of  sulphuric  or  muriatic  acid.  Soon  an  oily  liquid  rises  to  the 
surface,  which, when  applied  upon  the  arm,  produces  in  the  course 
of  three  or  four  hours  not  only  inflammation,  but  also  the  pustu- 
lar eruption  peculiar  to  the  effects  of  croton  oil.  If  the  quantity 
was  small,  the  acidulated  liquid  was  shaken  with  strong  ether, 
the  ether  evaporated,  and  the  residue  applied. 
For  castor  oil,  and  in  the  presence  of  volatile  oils,  I  have  em- 
ployed diluted  alcohol,  mixed  with  an  alcoholic  solution  of 
potassa,  and  omitted  the  dilution  of  the  decanted  alcoholic  liquid- 
