148 
Manufacture  of  Acetone. 
(  Am.  Jour.  Pharm. 
I      March.  1895. 
tion  can  be  expected  only  from  uniformity  of  heating.  And  the  differences  in 
the  degrees  of  heat  required  to  produce  the  different  reactions  here  do  not 
seem  to  be  great. 
The  physical  and  mechanical  conditions  of  heating  a  stationary  tube  cannot 
possibly  yield  an  equal  degree  of  heating  to  the  contents  of  such  tube,  espe- 
cially where  only  a  part  of  such  contents  is  in  motion.  Even  if  the  whole  out- 
side of  the  tube  could  be  equally  heated— as  it  could  not  be  practically  — the 
contents  would  be  cooler  from  circumference  to  centre.  But  in  this  case,  where 
a  current  of  vapor  at  about  ioo°  C.  is  passed  continually  into  a  tube,  the  out- 
side of  which  is  kept  unequally  heated  to  500  or  66o°  C,  and  where  this  current 
has  to  find  its  way  at  varying  speed  through  varying  friction  and  expansion, 
only  a  varying  decomposition  can  be  possible,  and  the  conclusion  must  be  that 
if  uniform  decomposition  is  to  be  reached  it  must  be  through  uniform  con- 
ditions. 
Equable  heating  in  a  stationary  tube,  under  the  conditions  of  this  process, 
being  impracticable,  it  became  necessary  to  devise  some  better  form  of  still; 
and  a  careful  consideration  of  the  principles  involved,  and  the  especial  me- 
chanical difficulties  of  this  decomposition,  led  the  writer  to  a  form  of  rotary 
still,  which,  after  some  alterations  and  modifications,  has  proved  successful. 
A  wrought-iron  tube  about  36  Cm.  (14  inches)  long  by  12*7  Cm.  (5  inches)  in 
diameter,  contracted  at  the  ends  to  central,  hollow  journals  of  about  2  Cm. 
(o'75  inch)  external  diameter  and  1*2  Cm.  (0*5  inch)  bore,  free  to  revolve,  was 
supported  in  the  centre  of  the  18  Cm.  (7  inch)  drain  pipe  furnace,  and  connected 
at  one  end  with  the  vapor  supply,  and  the  other  with  the  condensers  by  air- 
tight glands  or  "  stuffiing-boxes. "  The  ends  were  provided  with  charging  and 
discharging  openings  which  could  be  closed  air-tight,  and  the  still  was  revolved 
slowly  by  means  of  a  pulley  on  one  end  of  the  hollow  shaft.  A  small  stationary 
tube  passed  into  the  still  through  the  revolving  shaft  to  convey  the  acid  vapor 
to  the  entrance  of  the  still  at  one  end,  and  a  similar  tube  gave  exit  to  the  pro- 
ducts of  the  decomposition  at  the  other,  condenser  end.  It  was  necessary  to 
protect  this  tube  from  obstruction  by  dust  carried  by  the  current  of  vapors,  and 
this  was  done  by  a  cartridge  of  rolled-up,  wire  cloth  filled  with  glass  wool. 
This  rotary  still  was  driven  at  the  rate  of  three  to  six  revolutions  per  minute  by 
a  small  water-motor,  and  was  found  to  heat  with  great  equability  as  it  revolved 
over  the  burners.  Inside  of  the  still,  at  equal  distances  apart  on  the  periphery, 
five  Iv-shaped,  longitudinal  strips  of  sheet-iron  were  riveted.  These  were  nec- 
essary to  prevent  the  charge  from  sliding  round  as  the  iron  became  smooth, 
and  they  were  found  to  carry  the  charge  round,  turn  it  over  and  mix  it  most 
effectively  at  each  revolution.  Thus,  while  by  the  revolutions  over  the  source 
of  heating  the  shell  was  heated  very  uniformly,  this  continuous  moving  and 
turning  over  of  the  contents  must  bring  all  parts  of  the  charge,  solids  and 
vapors  alike,  in  successive  contact  with  the  hot  surfaces  and  the  cooler  atmos- 
phere of  the  still,  and  thus  secure  a  fair  degree  of  equable  heating.  The  still 
being  about  one-third  filled  with  the  solid  charge  and  slowly  rotated,  the  charge 
occupies  principally,  not  the  bottom  of  the  still  directly  over  the  fire,  but  the 
ascending  third  which  has  just  been  over  the  fire.  Then,  as  the  charge  is  car- 
ried up,  the  superficial  cooler  portion,  too  deep  to  be  held  by  the  longitudinal 
shelves,  slides  back  onto  the  hot  surface  below,  while  the  portion  carried  on 
by  the  shelves  falls  back,  shelf  by  shelf,  from  contact  with  the  hot  shell  through 
