408  ON  THE  FIXED  OIL  OF  ALMONDS. 
which  a  thermometer  is  inserted,  while  the  vessel  is  covered  with, 
paper.  The  purest  acid  was  obtained  by  mixing  the  resin  with 
an  equal  weight  of  crude  oil  of  vitriol  free  -from  nitric  acid  ;  this 
mixture,  put  into  a  leaden  vessel,  is  placed  into  the  iron  or  cop- 
per vessel  and  then  slowly  heated  to  the  above  temperature  to 
prevent  its  foaming  over. — Zeitsc]i7\  /.  Cliemie  1870,  loart  9, 
278.  J.  M.  M. 
ON  THE  FIXED  OIL  OF  ALMONDS. 
By  Dr.  H.  Eager. 
There  is  a  considerable  difference  between  the  fixed  oil  ex- 
pressed from  the  large  sweet  and  from  the  smaller  bitter  almonds, 
which  is  readily  shown  by  the  elaidin  test :  the  former  oil  con- 
geals more  rapidly  and  almost  completely ;  while  the  latter  con- 
geals about  twelve  hours  later  and  the  more  imperfectly,  the 
smaller  the  bitter  almond  has  been.  The  column  of  elaidin  in 
the  test  tube  obtained  from  the  oil  of  the  sweet  and  large  sized 
bitter  almonds  is  whitish  or  yellowish,  of  the  smaller  bitter 
almonds  more  yellow  or  brownish  and  surrounded  by  one  or  two 
thin  liquid  layers,  proving  that  this  oil  approaches  the  drying 
oils.  Only  about  one-third  of  its  bulk  congeals  if  the  oil  is  from 
the  small  Oporto  almond. 
For  medicinal  purposes  this  difference  between  the  almond 
oils  is  probably  immaterial,  since  no  distinction  has  heretofore 
been  made  between  them.  But  for  the  last  twenty  years  an 
almond  oil  is  in  the  market  which  yields  yellow  or  brown  elaidin, 
surrounded  by  thickish  liquid  layers,  and  which,  in  Hamburg 
and  other  places,  is  prepared  in  large  quantities  from  peach 
seeds,  but  sold  as  01.  amygd.  optimum  or  verum. 
The  author  recommends  the  following  test  to  distinguish  true 
almond  oil  from  the  oil  of  peach  and  apricot  seeds  :  equal  volumes 
of  the  oil  and  25  per  cent,  nitric  acid  are  shaken  together  in  a 
test  tube ;  an  emulsion  like  mixture  is  obtained,  which  separates 
again  on  standing.  All  true  almond  oils  yield  a  purely  white  mix- 
ture, and  after  many  hours  the  separated  oil  is  still  white.  On 
heating  the  mixture  to  60°  C.  almond  oil  remains  white  or  be- 
comes faintly  yellowish  white. 
The  oils  of  peach  and  apricot  seeds  shaken  with  the  nitric 
