458         ON  A  PROCESS  OF  FRACTIONAL  CONDENSATION. 
tubes  extend  through  the  end  of  the  refrigerator  far  enough  to 
form  a  convenient  connection  with  the  second  receiver,  Z,  fig.  2, 
which  communicates  with  the  first  receiver,  k,  by  means  of  the 
glass  tube,  m. 
In  order  to  successfully  collect  and  condense  the  vapors  of 
such  extremely  volatile  liquids  as  are  now  under  consideration, 
it  is  of  course  indispensable  that  the  apparatus  should  be  con- 
structed with  very  tight  joints  ;  and  for  greater  convenience, 
but  more  especially  to  prevent  breakage,  such  of  the  joints  as 
require  to  be  frequently  taken  apart  should  be  made  flexible.  A 
very  convenient  and  perfectly  tight  joint  of  this  kind  may  be 
made  as.  follows  : — the  short  stationary  tube,  n,  in  the  cork  of 
the  receiver,  k,  fig.  2,  is  made  with  the  opening  somewhat  diver- 
gent upward  ;  the  end,  o,  of  the  worm  is  enough  smaller  than 
the  inside  diameter  of  the  upper  end  of  the  tube,  n,  to  leave 
room  for  a  piece  of  caoutchouc  tube  to  be  drawn  over  it,  and 
still  admit  of  its  being  inserted  in  the  end  of  the  tube,  n  ;  the 
flexible  tube  is  drawn  on  far  enough  to  prevent  the  drops  which 
form  on  the  end  of  the  worm  from  coming  in  contact  with  the 
caoutchouc ;  a  perfectly  tight  and  convenient  flexible  joint  is 
now  made  by  pressing  the  tube,  n,  over  the  caoutchouc  covering 
of  the  end  of  the  worm,  o.  The  joints  of  the  receivers,  U,  are 
made  in  the  same  manner. 
The  vapors  which  escape  condensation  in  ii  pass  through  the 
receivers,  kk  and  U,  to  the  refrigerator,  B,  which  contains  ice, 
or  a  mixture  of  ice  and  salt,  are  there  condensed  and  fall  back 
into  the  receivers,  11 ;  which  should  stand  in  a  wooden  vessel 
also  containing  ice  or  a  freezing  mixture.  The  refrigerator,  B, 
is  made  with  double  bottom  and  sides,  with  an  inch  space  be- 
tween, which  is  filled  with  pulverized  charcoal.  Being  tightly 
covered,  a  charge  of  ice  and  salt  will  serve  for  a  long  day's 
operations  without  renewal.  In  this  manner  I  have  been  able 
to  collect,  in  considerable  quantity,  bodies  boiled  nearly  at  0°  C, 
and  this  from  mixtures  in  which  such  bodies  had  been  quite  over- 
looked by  previous  investigators. 
It  will  be  observed  in  reference  to  fig.  2,  that  the  larger  dis- 
tilling apparatus  is  represented  as  standing  in  a  brick  fire-place, 
with  brick-work  CC,  a  few  inches  high,  built  up  in  front ;  and 
