In  1853  R.  A.  Tilghman  discovered  that  fatty  acids  could  be
separated  from  glycerin,  without  injury  to  the  latter,  by  the  single
and  simple  process  of  subjecting  the  neutral  fat  while  in  intimate
mixture  with  water  to  a  high  degree  of  heat,  under  sufficient  pressure
to  prevent  the  water  from  being  converted  into  steam,  without  the
•employment  of  any  alkali  or  sulphuric  acid  or  other  saponifying
agent,  the  operation,  even  with  the  most  solid  fats,  being  capable
of  completion  in  a  very  few  minutes  when  the  heat  applied  is  equal
to  that  of  melting  lead,  or  612°  Fahr.,  but  requiring  several  hours
when  it  is  as  low  as  350°  or  400°  Fahr.  The  only  conditions  are  a
constant  and  intimate  mixture  of  the  fat  with  the  water,  a  high
degree  of  heat,  and  a  pressure  sufficiently  powerful  to  resist  the


CANDLES.  443

conversion  of  the  water  into  steam.  The  result  was  a  decomposition
of  the  fatty  body  into  its  elements  of  glycerin  and  fatty  acids,  each
element  taking  up  the  requisite  equivalent  of  water  essential  to  its
separate  existence,  and  the  glycerin  in  solution  separating  itself
from  the  fatty  acids  by  settling  to  the  bottom,  when  the  mixed  prod-
ucts are  allowed  to  stand  and  cool.  In  this  process  a  chemical
change  took  place  in  the  fat  in  consequence  of  the  presence  of  the
water  and  the  active  influence  of  the  heat  and  pressure  upon  the
mixture.  In  1854  Tilghman  patented  his  discovery  in  England
and  in  the  United  States.
However,  owing  to  the  incomplete  saponification  and  the  de-
struction of  the  fatty  acids,  the  industrial  application  of  this  process
was  not  successful.
Chevreul's  lime-saponification  process  and  the  sulphuric-acid
distillation  process  were  the  only  two  processes  practically  used
down  to  the  time  of  Tilghman's  invention.
