658         Isothermal  Distillation  of  Argon  and  Oxygen. 
lines  which  are  drawn  to  show  what  the  partial  pressures 
would  be  if  they  were  proportional  to  the  molecular  per- 
centage. It  will  be  noticed  also  that  the  partial  pressure  of 
oxygen  above  the  saturated  solution  is  much  less  than  would 
be  expected  from  analogy  with  the  nitrogen-oxygen  curve. 
Fiff.  3. 
--4II  7717710. 
300 
92-7  . 
/?/?.  mo  is  %  Sat?  Sol- 
Argon  and  Oxygen  at  82o,09  Abs. 
This  shows,  therefore,  that  the  separation  of  a  solid  from  a 
liquid  in  which  it  is  soluble  is  a  much  more  complicated  dis- 
tillation-process than  the  separation  of  two  liquids.  A 
simple  separation  can  be  obtained,  however,  if  one  can  lower 
the  temperature  so  far  that  the  vapoar-pressure  of  the  pure 
solid  is  negligible  compared  with  the  vapour-pressure  of  the 
other  substance.  In  this  case  a  single  distillation  effects  a. 
complete  separation,  and  therefore  in  practice  one  always 
endeavours  to  obtain  this  condition  of  affairs. 
In  conclusion,  I  wish  to  express  my  thanks  to  Sir  William 
Hamsay  for  the  kind  interest  he  took  in  this  research. 
University  College, 
London,  W.C. 
