602 
Linseed  Oil. 
Am.  Jour.  Fharm. 
Dec,  1887. 
ding  more  it  still  remains  clear  until  two  volumes  have  been  added, 
when  it  becomes  turbid,  and  most  of  the  oil  separates  on  standing. 
Ten  gm.  were  similarly  extracted  with  carbon  disulphide,  the  yield 
being  33.50  per  cent.  The  oil  differed  only  from  the  above  in  color, 
which  was  of  a  yellowish-brown.  It  is  well  known  that  petroleum 
ether,  in  presence  of  fixed  oils,  will  dissolve  substances  which  ordi- 
narily are  insoluble  in  it,  and  it  is  very  likely  that  a  small  quantity  of 
chlorophyll  was  extracted  by  it  and  not  by  the  carbon  disulphide. 
Both  of  the  solvents  acted  at  an  elevated  temperature  and  removed 
all  of  the  fixed  oil,  as  when  reverse  extractions  were  made,  nothing 
additional  was  dissolved.  The  oils,  therefore,  were  identical,  and, 
after  this  point  had  been  decided,  the  experiments  were  made  only 
with  oil  extracted  by  means  of  petroleum  ether. 
The  variability  of  commercial  linseed  oil,  in  regard  to  solubility  in 
absolute  alcohol,  has  been  attributed  to  the  supposed  fact  that  the  oil 
differed  in  composition  when  expressed  in  the  cold  or  with  the  aid  of 
heat.  In  cases  where  solvents  were  used  it  has  been  supposed  that  sol- 
vents of  different  composition,  or  boiling-point,  removed  only  portions 
of  the  oil.  If  these  views  be  correct,  the  first  and  last  portions  of  oil 
extracted  by  a  solvent  should  differ  in  regard  to  the  solubility  in  abso- 
lute alcohol.  That  these  portions  and  the  total  oil  are  completely  and 
easily  soluble  in  all  proportions  of  absolute  alcohol,  clearly  prove  that 
the  above  views  are  erroneous,  and  that  the  pharmacopoeial  test  is  a 
valuable  one  for  oil  gotten  by  aid  of  a  solvent  or  by  cold  expression, 
not  followed  by  any  other  treatment. 
In  the  manufacture  of  the  oil  it  is  customary  to  first  roast  the  seed, 
in  order  to  coagulate  albuminous  substances  and  to  render  insoluble 
the  gum  present.  After  the  extraction  of  the  oil  this  is  bleached  or 
decolorized  by  the  use  of  sulphuric  acid :  and,  here  it  was  thought 
might  be  found  the  key  to  explain  the  differences  shown  by  the  com- 
mercial oil. 
In  the  U.  S.  Dispensatory  is  given  a  process  by  Mr.  C.  Puscher, 
for  the  bleaching  of  flaxseed,  rapeseed  and  poppyseed  oils,  which  con- 
sists in  adding  to  the  oil  two  per  cent,  of  a  mixture  of  equal  parts  by 
weight  of  sulphuric  acid  and  alcohol,  allowing  to  stand  until  the  oil 
becomes  clear,  which  requires  from  twenty-four  to  forty-eight  hours, 
and  thoroughly  washing  with  hot  water. 
To  test  the  action  of  sulphuric  acid  upon  oil — which  was  known  to 
be  pure,  which  dissolved  in  all  proportions  in  absolute  alcohol  and 
