632  Methyl  Alcohol  and  Ethyl  Alcohol.  {^EiplmiJ,\'^^: 
ing  to  the  oven.  All  the  ovens  in  the  plant  have  the  cars  so  placed 
before  them,  usually  some  little  time  before  the  cars  are  actually 
run  in,  so  that  the  ovens  may  all  be  recharged,  one  after  another, 
without  the  loss  of  time  between.  After  the  cars  have  been  placed 
in  the  ovens,  the  doors  on  the  ovens  are  closed  and  the  process  of 
carbonization  is  begun. 
Ovens.- — Ovens  are  of  varying  sizes,  from  i  to  lo  cords  capacity, 
and  usually  have  a  door  at  each  end,  so  that  cars  may  be  run  straight 
through,  thus  obviating  the  necessity  of  turn-tables  or  transfer 
tables.  Their  construction  is  very  strong  and  rigid.  Steel  hangers 
are  riveted  to  the  sides,  and  each  hanger  is  supplied  with  shackle, 
U-bolt  and  suspension  washer,  the  purpose  of  the  hangers  being  to 
allow  the  oven  to  expand  and  contract  without  restriction.  Inside 
of  the  oven,  there  is  a  track  for  the  cars  to  run  upon,  and  this  is  made 
so  that  it  can  expand  and  contract  independently  of  the  expansion 
and  contraction  of  the  oven  itself.  The  doors  and  frames  are  of 
cast  iron,  while  the  remaining  portion  of  the  oven  is  of  steel. 
The  doors  are  hinged  and  when  closed  are  held  in  place  with 
tapered  keys,  which  are  easily  inserted  and  easily  withdrawn.  The 
door  joints  are  tongued  and  grooved  and  made  tight  with  asbestos 
packing.  They  are  set  in  pairs  and  are  bricked  in.  There  is  a 
smokehood  to  provide  egress  from  the  building  of  smoke  and  gases 
which  issue  from  the  oven  when  the  discharge  end  door  is  open, 
and  the  cars  are  being  pulled  out.  One  smoke  stack  is  required  for 
two  ovens,  and  this  is  placed  in  the  center  of  the  setting.  Ducts  are 
provided  in  the  brick  work  to  properly  convey  the  smoke  into  this 
stack.  Dampers  are  furnished  to  give  desired  control,  and  indi- 
vidual control  of  each  oven  may  be  had.  There  are  clean-out  doors 
on  the  sides  of  the  settings,  both  below  and  above  the  ovens.  Above 
the  ovens  is  a  drying  floor. 
Carbonizing  Process. — It  requires  from  1 8  to  24  hours  to  carbonize 
one  charge  of  wood  in  an  oven  retort.  During  this  period,  the  fires 
in  the  furnaces  are  kept  burning  continuously,  but  the  tempera- 
ture is  allowed  to  gradually  rise  from  the  beginning  of  a  charge  to 
its  maximum  point,  which  is  reached  from  six  to  eight  hours  after 
the  beginning.  Then  the  maximum  temperature  is  maintained  for 
a  variable  period,  and  finally  the  furnace  fires  are  allowed  to  go  down 
and  the  temperature  in  the  ovens  gradually  decreases  until  the  end 
of  the  run.  The  latter  end  of  the  distillation  is  accomplished  by 
the  latent  heat  in  the  ovens  and  their  settings. 
