ON  A  PROCESS  OF  FRACTIONAL  CONDENSATION,  455 
brazed  so  that  they  will  bear  a  high  temperature.  1  generally 
use,  also,  copper  worms,  especially  in  the  earlier  distillations, 
the  quantities  then  operated  upon  being  larger,  as  such  worms 
are  conveniently  procured,  and  not  liable  to  break.  In  the 
larger-sized  apparatus,  the  tube  of  which  the  worm  is  made 
measures  ten  feet  in  length  and  half  an  inch  in  diameter.  I 
have  tried  several  lengths  of  worm  and  several  diameters  of 
tube,  but  not,  as  yet,  with  any  special  view  of  determining  the 
precise  proportions,  in  relation  to  the  size  of  the  retort,  which 
would  be  best  adapted  to  the  purpose.  There  appears,  however, 
to  be  nothing  gained  by  increasing,  the  length  of  the  worm  be- 
yond what  is  required  to  reduce  the  temperature  of  the  vapors 
to  that  of  the  bath.  I  have  in  use  three  sizes  of  apparatus  :  the 
largest  has  a  copper  worm  10  feet  long  and  J  inch  bore  ;  the 
medium  size,  a  worm  5  feet  long  and  f  inch  bore ;  and  the 
smallest  size,  for  very  small,  quantities,  a  worm  1  foot  6  inches 
long  and  J  inch  bore.  Each  of  these  has  been  found  to  answer 
a  good  purpose.  The  distillation  may  be  conducted  in  a  glass 
flask,  or  more  conveniently  in  a  glass  retort  of  the  form  shown 
at  d,  figs.  1  and  2.  The  body  of  this  retort,  as  appears  in  the 
figure,  is  of  the  form  of  the  corresponding  part  of  the  common 
retort ;  but  which,  in  place  of  a  long  neck,  has  only  a  short  tu- 
bulure,  e,  in  the  side,  for  escape  of  the  vapors,  and  another  tubu- 
lure,  /,  in  the  top,  which  contains  the  thermometer,  and  through 
which  the  retort  is  charged. 
In  the  larger  apparatus  the  retort  is  connected  with  the  lower 
end  of  the  elevated  worm  by  means  of  a  glass  tube  of  about  the 
same  diameter  as  the  end  of  the  worm.  One  end  of  this  tube 
enters  the  retort  at  the  lateral  tubulure  through  a  perforated 
cork,  and  the  other  end  is  joined  to  the  end  of  the  worm,  either 
by  being  firmly  bound  with  a  strip  of  cloth  thickly  covered  with 
vulcanized  caoutchouc, — such  as  is  found  in  commerce, — or  by 
means  of  a  perforated  cork,  which  is  made  to  fit  the  ends  of  both 
tubes  as  snugly  as  possible,  and  then  tightly  pressed  togethe 
upon  the  joint  by  means  of  an  iron  clamp,  as  shown  at  (/,  fig.  2. 
This  clamp  is  figured  on  a  larger  scale  at  E.  As  it  is  highly 
important  that  all  joints  in  the  apparatus  should  be  perfectly 
tight,  inasmuch  as  the  least  leakage,  when  continued  a  long 
