622 
The  Alcohol  Test  for  Castor  Oil.      {Am  Dec"i8^.arm' 
1 500  F.,  the  rubber  under  the  copper  had  become  quite  hard,  that 
under  the  platinum  had  become  slightly  affected  and  hardened  at 
different  parts,  whilst  the  rubber  under  the  silver  and  under  the 
zinc  remained  quite  sound  and  elastic.  This  would  infer  that  the 
pure  metallic  copper  had  exerted  a  great  oxidizing  effect  on  the 
rubber,  the  platinum  had  exerted  a  slight  effect,  whilst  the  zinc  and 
silver  respectively  had  had  no  injurious  influence  on  it.  A  still 
more  curious  result  was  this,  that  the  rubber  thus  hardened  by  the 
copper  contained  no  appreciable  trace  of  copper ;  the  copper,  there- 
fore, presumably  sets  up  the  oxidizing  action  in  the  rubber  without 
itself  permeating  it. 
I  have  pleasure  in  acknowledging  the  assistance  rendered  to  me 
in  this  investigation  by  my  assistant,  Mr.  Frederick  Lewis. 
THE  ALCOHOL  TEST  FOR  PURE  CASTOR  OIL.1 
By  J.  Arthur  Wilson. 
Castor  oil  differs  in  many  respects  from  most  fixed  oils,  especially 
in  consisting  largely  of  the  glyceride  of  ricinoleic  acid,  which  is 
soluble  in  absolute  alcohol.  Hence  this  reagent  can  be  used  for  the 
detection  of  impurities  in  castor  oil.  Like  most  other  tests  of  a 
similar  kind,  it  is  not  of  much  use  for  the  detection  of  small  quan- 
tities of  foreign  oil,  owing  to  the  solvent  action  of  the  dissolved 
castor  oil  on  the  small  proportion  of  foreign  oil  that  may  be  present. 
The  British  Pharmacopoeia  directs  that  pure  castor  oil  shall  be 
soluble  in  an  equal  measure  of  absolute  alcohol  and  twice  the  mea- 
sure of  rectified  spirit. 
According  to  Mr.  Allen  ("Commercial  Organic  Analysis,"  vol.  ii, 
128)  this  is  correct  at  300  C,  providing  spirit  of  exactly  0-838  gra- 
vity be  used.  I  have  examined  a  number  of  samples  of  both  com- 
mercial and  medicinal  castor  oil,  strictly  at  300  C.,and  by  a  spirit  of 
exactly  0-838  specific  gravity,  and  find  that  at  exactly  300  C.  the  oil 
is  not  completely  soluble,  but  that  the  temperature  of  solution  varies 
between  380  and  43 0  C.  I  may  say  that  the  oils  I  used  satisfied  all 
other  requirements  as  to  purity. 
In  carrying  out  the  alcohol  test,,  it  is  best  to  operate  as  follows : 
One  measure  of  the  castor  oil  under  examination  is  mixed  thoroughly 
with  two  volumes  of  spirit  of  exactly  0-838  specific  gravity,  and  then 
1  Chetn.  News,  Oct.  31,  1890,  p.  215. 
