324  Manufacture  of  Chloroform.  {Am;JS^\m&Tm' 
secured  by  stirring  the  acetates  so  that  all  portions  of  the  mass  will  be 
subjected  to  the  heat  resulting  from  direct  contact  with  the  bottom  of 
the  vessel  and  by  admitting  free  steam  from  time  to  time  into  direct 
contact  with  the  acetates  in  case  of  any  undesirable  rise  in  temperature 
within  the  vessel." 
Fig.  2  shows  the  form  of  retort  in  which  this  is  effected.  It  will 
be  seen  mechanical  agitation  is  provided  for  by  the  paddles  which 
rotate  around  the  vertical  central  axis.  Steam  is  admitted  by  one  of 
the  openings  above,  while  the  products  of  distillation  pass  off  by 
Fig.  2. 
another  opening  in  the  top  of  the  retort.  The  crude  acetone  distillate 
so  obtained  while  richer  than  before  in  real  acetone  still  contains  oily 
distillation  products  and  much  water  from  condensed  steam.  In  this 
dilute  state  it  is  treated  with  milk  of  lime  to  remove  the  higher  ke- 
tones and  other  compounds.  It  is  then  distilled  from  a  large  plain 
still  and  the  fractions  rich  in  acetone  passed  to  a  column-still  where  it 
is  rectified  until  it  becomes  almost  if  not  quite  anhydrous.  In  prac- 
tice, two  column-still  rectifications  are  carried  out,  one  after  the  other, 
so  that  the  pure  acetone  shows  99°  or  100°  by  the  alcoholometer.  It 
is  now  fitted  for  use  in  the  direct  manufacture  of  chloroform.  The 
