FATTY  ACIDS  FOR  THE  MANUFACTURE  OF  CANDLES. 
63 
from  the  boiler,  passes  through  a  series  of  iron  pipes  heated  in  a 
furnace.  The  quantity  of  acid  used  is  in  the  proportion  of  6  lbs. 
for  112  lbs.  of  palm-oil.  In  this  operation  the  palm-oil  is  decom- 
posed and  becomes  much  blackened.  Withdrawn  at  that  period  it 
is  seen  that  an  important  change  has  been  effected  by  the  action 
of  the  acid,  as  the  mass  now  readily  crystallizes  to  a  tolerably 
solid  fat.  The  fat  is  now  drawn  off  from  the  acid  and  transferred 
to  the  washing-tank,  where  it  is  boiled  up  with  water  by  means  of 
a  steam-jet. 
Distillation. — After  one  or  two  washings  the  blackened  fat  is 
withdrawn  and  pumped  up  to  the  supply-tank,  which  commands  the 
stills.  The  stills,  which  are  made  of  copper,  are  heated  by  an 
open  grate;  each  still  is  capable  of  holding  five  tons  of  fat.  When 
charged,  the  temperature  is  raised  to  293.5°  Cent.  (560°  F.),  and 
low-pressure  steam  passed  through  the  mass.  This  steam  is  pre- 
viously heated  by  passing  through  a  system  of  iron  pipes  placed 
in  a  furnace. 
The  current  of  steam  carries  with  it  the  vapor  of  the  fatty 
acids,  and  thus  facilitates  the  process.  The  mixed  vapors  of  fatty 
acids  and  waters  pass  together  to  a  series  of  vertical  pipes,  which 
retain  a  temperature  above  100°  Cent.  (Cent.  212°  F.),  where  the 
fats  only  condense  while  the  steam  passes  to  a  second  refrigerator, 
cooled  by  a  current  of  water ;  here  it  is  condensed  along  with  the 
minute  quantity  of  fat  carried  over  by  it.  A  separating  tank,  from 
which  the  water  escapes  at  the  bottom,  whilst  the  fats  float  on  the 
top,  serves  to  remove  this  small  quantity. 
Distillation  of  the  Residue. — After  continuing  the  distillation 
for  a  certain  period,  the  residue  in  the  still  is  transferred  to  another 
still,  formed  of  iron  pipes,  set  in  a  furnace,  and  there  submitted  to 
a  much  higher  temperature,  and  a  jet  of  steam  more  strongly 
heated.  The  residue  left  in  these  iron  stills  is  a  sort  of  pitch,  and 
is  applied  to  the  same  use  as  ordinary  pitch.  By  this  means  an 
additional  quantity  of  fatty  acids  is  obtained. 
The  fatty  acids,  as  they  run  from  the  still,  are  used  to  a  great 
extent  for  the  manufacture  of  candles,  without  pressing,  and  form 
what  are  called  composite  candles,  which  possess  all  the  advantages 
of  being  self-snuffing,  but  are  more  fusible  and  softer  than  the 
pressed  stearic  acid  candles. 
