FATTY  ACIDS  FOR  CANDLE  AND  SOAP  MAKING.  435 
dually  reject  the  lixivium  with  which  they  were  distended,  re- 
taining only  the  quantity  of  water  always  entering  into  the 
composition  of  soap.  They  then  become  transparent,  semi- 
liquid,  and  their  confused  mass  forms  a  layer  of  melted  soap 
above  the  lixivium,  which  contains  the  glycerine. 
4th.  The  saponification  of  this  mass  is  so  complete  that  to 
extract  the  stearic  acid,  it  is  only  necessary  to  dilute  the  soap 
in  cold  water,  and  acidulate  with  a  quantity  of  sulphuric  acid 
proportioned  to  the  soda.  The  fatty  acids,  mixed  with  water 
charged  with  sulphate  of  soda,  may  be  separated  by  melting 
and  pressing  when  cold,  to  obtain  stearic  acid,  inodorous  and 
fusible  at  from  58°  to  59°,  and  almost  colorless  oleic  acid. 
These  results,  tested  by  industrial  experience,  recall  the 
time  when  M.  Chevreul,  after  hi3  remarkable  investigation  of 
fatty  bodies,  believed  that  stearic  acid  could  be  economically 
produced  with  oleic  acid.  Unfortunately,  all  attempts  to  carry 
out  this  idea  have  failed. 
Thus  lime  has  been  employed,  the  soap  of  which  decomposes 
only  by  very  strong  measures,  giving  rancid,  colored  oleic  acids, 
whilst  producing  a  loss  in  the  deposits  of  sulphate  of  lime,  with- 
out counting  a  number  of  costly  operations  ;  then  came  distilla- 
tion, which  increased  the  loss  from  10  to  15  per  cent.,  and 
lowered  the  value  of  the  product  so  much,  that  one  part  of 
stearic  acid  disappeared,  and  the  oleic  acid  was  rejected  on  ac- 
count of  its  odor,  its  color,  and  its  inapplicability  for  making  an 
agreeable  soap  ;  then  came  the  splitting  up  of  the  fatty  body  by 
water  under  pressure  ;  but  then  the  incomplete  saponification  and 
diffused  crystallization  became  an  obstacle  to  all  subsequent 
operations.  Finally,  instead  of  pure  water,  a  small  proportion  of 
lime,  soda,  or  soap  was  put  in  the  digester.  The  saponification 
still  remained  incomplete ;  the  decomposing  and  pressing  ope- 
rations gave  the  same  results  in  this  as  in  the  preceding  in- 
stances, yielding  only  a  kind  of  stearic  acid,  with  a  very  low 
fusing  point,  and  a  red  oxidised  oleic  acid  to  the  value  of  85  or 
88  frs.,  while  the  olive  oil  was  worth  130  and  135  frs.  (These 
various  operations  have  been  described  by  MM.  Pelouze,  Til- 
man,  Melsens,  Podwer,  &c.) 
In  the  new  operation  all  this  is  reversed  ;  the  loss  is  nil,  be- 
ing limited  to  the  subtraction  of  the  glycerine ;  the  quantity  of 
