276 
rochleder's  proximate  analysis. 
a  hydrocarbon,  or  a  mixture  of  several  hydrocarbons.  On  the  contrary, 
if  that  oil  reacts  on  the  potassium  or  sodium,  an  oxygenated  body,  or  a 
mixture  of  several  such  bodies,  is  present. 
To  prove  whether  or  not  the  oxygenated  body  present  is  a  compound 
ether,  the  oil  under  examination  is  divided  into  two  parts.  One  portion  is 
treated  with  caustic  ammonia  in  a  small  flask,  by  which,  in  many  cases, 
an  amide  of  the  acid  of  the  ether  separates,  while  the  alcohol  correspond- 
ing to  the  ether  becomes  free.  The  second  portion  of  the  oil  is  introduced 
with  baryta  water  into  a  small  retort,  a  little  of  the  crystals  of  hydrate  of 
baryta  thrown  in,  and  the  retort  so  connected  with  a  small  Liebig's  refriger- 
atory apparatus  that  the  condensed  vapors  are  compelled  to  flow  back 
again  into  the  retort,  when  the  contents  of  the  letort  are  heated  to  the 
boiling  point.  When  the  ebullition  has  been  continued  for  some  time,  the 
refrigeratory  apparatus  is  brought  into  its  ordinary  position,  and  the  dis- 
tillation proceeded  with.  The  hydrocarbons  present,  as  well  as  the  indiffer- 
ent oxygenated  oils,  pass  over  with  the  aqueous  vapor  ;  likewise  the  al- 
cohols derived  from  the  ethers.  The  acids  of  the  ethers  remain  behind, 
combined  with  the  baryta.  The  residue  of  the  retort  is,  when  cold,  re- 
moved, and  the  baryta  separated  from  the  liquid,  which,  when  necessary, 
should  previ(jusly  be  filtered,  by  means  of  dilute  sulphuric  acid.  After 
separating  the  sulphate  of  baryta  by  a  filter,  the  liquid  is  again  dis- 
tilled, whereby  the  acid  contained  either  in  the  distillate  in  which 
its  presence  may  be  easily  detected,  or  when  it  is  not  distillable  with 
water,  its  concentrated  solution  remains  behind  in  the  retort.  From 
this  fluid  the  acid,  under  proper  conditions,  mny  be  crystallized  out.  The 
existence  of  compound  ethers  in  the  oil,  separated  from  the  distillate,  is 
not  very  frequent,  as  the  majority  of  ethers,  being  readily  soluble  in 
water,  are  found  dissolved  in  the  aqueous  distillate. 
If  no  compound  ether  is  present,  it  is  still  to  be  determined  whether 
an  oxygenated  indifferent  volatile  oil  is  admixed  with  hydrocarbons  or  not, 
which  was  partly  discoverable  from  the  treatment  of  the  oil  with  potassium 
or  sodium.  To  detect  such  body,  the  oil  to  be  examined  is  introduced  into 
a  small  retort,  which  is  half  filled  with  coarsely  powdered  soda-lime.* 
The  oil  is  absorbed  by  the  soda-lime.  After  a  flask,  as  a  receiver,  has 
been  adjusted,  the  retort  is  carefully  heated.  The  hydrocarbons  will  be 
distilled  over,  unchanged  in  their  composition,  while  the  oxygenated  oils 
will  be  decomposed  by  the  action  of  the  alkaline  compound.  Generally, 
non-volatile  compounds  result  therefrom,  which  only  are  decomposed  by 
higher  temperatures,  under  the  formation  of  volatile  compounds.  Ger- 
hardt  and  Cahours,  in  this  way,  have  separated  the  hydrocarbons  from 
*  Soda-lime  is  made  by  mixing  lime  with  a  solution  of  caustic  soda,  in  such 
proportion  that,  upon  evaporation,  the  mixture,  when  heated  to  redness,  shall 
be  equivalent  to  one  part  of  the  hydrate  of  soda,  with  two  parts  of  anhydrous 
lime.— Editor  Pharm.  Jour. 
