BEHAVIOUR  OF  PALM  OIL  WHEN  HEATED. 
347 
kept  for  ten  minutes  at  a  temperature  of  464°  F.,  and  the  bleach- 
ing is  then  completed.  Ten  or  twelve  hundredweights  of  palm- 
oil  may  be  conveniently  heated  in  one  pan,  which  must,  however, 
only  be  two-thirds  filled,  as  the  palm-oil  expands  greatly  by  the 
heat.  It  must  be  covered  with  a  well-fitted  cover,  which  prevents 
inconvenience  from  the  above  mentioned  acid  fumes.  The  palm- 
oil  acquires  a  purer  white  color  when  operated  upon  on  a  large 
scale,  than  when  treated  in  small  quantities;  it  furnishes  a  very 
fine,  solid  white  soap.  The  empyreumatic  odor  which  occurs  im- 
mediately after  the  bleaching,  is  lost  after  some  time,  and  the  ori- 
ginal violet-like  odor  of  the  palm-oil  again  returns.  The  soap 
prepared  from  it  has  also  a  pleasant  violet-like  odor,  as  the  em- 
pyreumatic smell  entirely  disappears  during  saponification.  Palm- 
oil  which  is  much  contaminated  with  vegetable  matters  should  be 
melted  at  a  lower  temperature  before  bleaching,  so  as  to  allow  the 
impurities  to  settle.  The  best  samples  of  palm-oil  never  contain 
more  than  from  0*3  to  1*0  per  cent,  of  such  impurities. 
If  palm-oil  be  heated  to  572°  F.  with  access  of  air,  it  beginsto 
boil,  and  a  strong  odor  of  acroleine  is  perceptible.  Distillation, 
carried  on  at  572°-592°  F.,  proceeds  very  slowly,  as  the  vapors 
formed  are  heavy  and  readily  condensable  ;  but  if  ordinary  steam 
be  allowed  to  flow  into  the  fatty  mass  heated  to  572°  F.,  the  dis- 
tillation takes  place  very  quickly.  At  the  commencement  of  boil- 
ing the  palm-oil  froths  much,  and  easily  passes  over  into  the  re- 
ceiver; but  in  a  few  minutes  this  frothing  ceases,  and  the  distilla- 
tion goes  on  without  further  disturbance.  • 
The  author  has  effected  the  distillation  of  quantities  of  from  30 
to  50  pounds  of  palm-oil.  If  the  fat  be  in  contact  with  atmos- 
pheric air  at  the  point  of  distillation,  acroleine  is  formed  with  the 
mixture  of  fatty  acids  which  passes  over.  The  action  of  this  sub- 
stance on  the  lachrymal  glands  and  the  organs  of  smell  and  respi- 
ration is  terrible.  The  same  odor  is  acquired  under  these  circum- 
stances by  the  products  of  distillation,  and  they  cannot  be  freed 
from  it  even  by  boiling  with  water.  But  if  care  be  taken  that, 
when  palm-oil  has  reached  the  temperature  of  572°  F.,  all  atmos- 
pheric air  shall  have  been  expelled  from  the  apparatus  by  Steam, 
not  the  smallest  odor  of  acreoline  makes  its  appearance  during  the 
distillation,  wThich  takes  place  without  any  trouble  to  the  work- 
man. At  the  end  of  the  operation,  a  blackish-brown  fluid  remains 
in  the  distilling  vessel,  which  on  cooling  sets  into  a  tough  and 
