274 
rochleder's  proximate  analysis. 
After  the  principal  bulk  of  the  water  has  been  removed  by  a  syphon,  its 
complete  removal  is  effected  by  means  of  a  separatory  funnel  or  a  pipette. 
The  water  is  then  treated  precisely  as  when  no  layer  has  been  separated 
on  the  surface  or  at  the  bottom.  This  method  of  treatment  is  described  at 
length  further  on. 
a. — Examination  of  the  separated  oil. 
It  is  first  ascertained  whether  the  separated  oil  reacts  on  litmus  paper  or 
riot.  If  the  blue  litmus  paper  is  reddened  thereby,  the  oil  is  either  a  vola- 
tile acid  or  a  mixture  of  several  volatile  acids,  or  lastly  a  mixture  of  one 
or  several  volatile  acids  with  other  volatile  bodies.  It  is  scarcely  neces- 
sary to  remark  that,  besides  the  peculiar  volatile  acids,  some  aldehydes 
also  may  be  present ;  for  example,  salicylous  acid  as  well  as  the  acid 
ethers  of  bibasic  acids — as,  for  instance,  the  acid  salicylate  of  methyloxide, 
which  is  obtained  by  the  distillation  of  Gaultheria  procumbens,  and  which 
behave  in  this  and  other  respects  as  volatile  acids. 
If  ike  oil  has  an  acid  reaction,  the  oil  is  introduced  into  a  flask,  and  ba- 
rvta  water  added  thereto  with  agitation.  This  addition  is  continued  until 
it  has  no  longer  an  acid  reaction  ;  afterwards  it  is  allowed  to  precipitate 
quietly.  Either  the  oil  has  quite  disappeared  by  this  treatment  with 
baryta  water — if  so  it  was  a  volatile  acid,  or  a  mixture  of  several  such 
acids,  or  an  acid  aldehyde  resembling  the  salicylous  acid,  or  an  acid 
ether,  possibly  a  mixture  of  several  aldehydes  or  ethers,  or  a  mixture  of 
several  members  of  these  two  classes  of  bodies,  or  of  all  three. 
The  oil  which  remains,  after  the  treatment  with  baryta  water,  is  neutral 
or  alkaline.  In  the  latter  case  it  is  treated  with  dilute  sulphuric  acid. 
When  a  volatile  base  is  present  therein,  it  dissolves  in  the  dilute  sulphuric 
acid.  If  absent,  as  much  oil  is  dissolved  as  would  be  dissolved  in  an 
equal  quantity  of  pure  water.  If  the  first  separated  oil  has  exhibited  an 
alkaline  reaction  instead  of  an  acid  one,  it  is  at  once  treated  with  dilute 
sulphuric  acid.  Either  a  complete  solution  of  the  oil  takes  place,  in  this 
case  an  organic  volatile  base,  or  a  mixture  of  several  such  bases  is  pre- 
sent, or  a  partial  solution  is  eff'ected  when  it  is  a  mixture  of  one  or  more 
volatile  bases  with  non-basic  bodies. 
As  we  learn  by  these  experiments  whether  bases  or  acids  are  at  the 
same  time  present,  or  bodies  which  behave  as  acids  towards  bases,  and  in 
case  such  bodies  were  found  they  have  been  removed  by  the  treatment 
with  sulphuric  acid  and  baryta  water,  we  now  proceed  to  detect  the  pre- 
sence of  the  aldehydes.  If  neither  an  acid  nor  a  base  is  present,  the  oil 
can  at  once  be  used  for  testing  for  aldehydes.  With  this  object,  a  portion 
of  the  oil  is  mixed  with  a  solution  of  the  bisulphite  of  potash  as  concen- 
trated as  possible.  When  an  aldehyde  is  present,  it  is  generally  taken  up 
by  the  solution  of  bisulphite  of  potash.  Either  a  portion  of  the  oil,  or  the 
whole  of  it,  is  dissolved,  depending  on  the  presence  of  indifferent  bodies, 
besides  one  or  more  aldehydes.    It  should  be  observed,  by  the  solution, 
