Am.  Jour.  Pharm. 
Dec,  1887. 
Linseed  Oil. 
603 
which  formed  a  clear  solution  with  an  equal  volume  of  95  per  cent, 
alcohol — some  prepared  by  extraction  with  petroleum  ether  was  taken 
and  mixed  with  the  requisite  amount  of  the  sulphuric  acid  and 
alcohol. 
After  fifteen  minutes'  contact  a  portion  was  thoroughly  washed 
and  tested  ;  it  had  not  been  altered. 
After  standing  five  hours,  another  portion  was  tried,  and  while  it 
showed  no  change  with  absolute  alcohol,  it  did  with  95  per  cent,  alco- 
hol, with  which  it  formed  a  clear  solution  until  an  equal  volume  had 
been  added,  when  it  became  turbid.  Testing  again  after  forty-eight 
hours,  the  oil  did  dissolve  in  five  parts  of  absolute  alcohol,  but  did  not 
dissolve  in  all  proportions ;  on  adding  a  few  drops  of  95  per  cent, 
alcohol  the  oil  formed  with  it  a  turbid  mixture,  and  did  not  dissolve 
on  adding  an  equal  volume.  These  experiments  show  that  the  action 
of  the  sulphuric  acid  decreases  its  solubility  in  proportion  as  the  con- 
tact is  more  prolonged,  and  explain  why  the  commercial  oil  varies  so 
greatly,  some  oils  becoming  decolorized  more  rapidly  than  others. 
Another  point  in  which  this  pure  oil  differs  from  the  commercial  is  its 
ready  saponification  at  the  temperature  of  the  water-bath  with  sodium 
carbonate.  This  is  the  only  fixed  oil  from  a  number  tried  which 
saponified  as  above.  The  pure  oil  saponified  with  sodium  hydrate, 
and  the  soap,  decomposed  by  hydrochloric  acid,  yields  acids  of  a  firmer 
consistency  than  the  acids  gotten  by  analogous  treatment  of  the  com- 
mercial oil.  The  acids,  when  heated  on  a  water-bath  with  a  little 
water  and  barium  carbonate,  liberate  carbon  dioxide ;  and,  if  the  ba- 
rium soap  be  washed  with  water  and  extracted  with  95  per  cent,  alco- 
hol, a  yellow  acid  solution  is  obtained  which  is  free  from  barium,  and, 
on  evaporation,  leaves  an  oily  acid.  The  portion  insoluble  in  alcohol, 
when  decomposed  by  sulphuric  acid,  separates  another  acid  of  a  firmer 
consistency  and  of  a  pale,  yellow  color.  This  forms  the  barium  salt, 
in  the  cold,  if  the  carbonate  be  mixed  with  it  in  presence  of  water. 
The  commercial  oil,  treated  in  the  same  manner,  appears  to  contain 
more  of  the  liquid  acid,  although  this  has  not  been  decided  by  actual 
quantitative  analysis. 
According  to  "Allen's  Organic  Commercial  Analysis,"  Vol.  II, 
linseed  oil  contains  linoleic  acid  C^H^C^,  having  a  saponification 
equivalent  of  264*7.  Allen  claims  the  presence  of  a  higher  homologue 
— homolinoleic  acid,  C18H3202 — the  claim  basing  on  the  fact  that  the 
saponification  equivalent  of  linseed-oil  varies  between  287  and  300  ; 
