Xitrogen  and  Oxygen  and  of  Argon  and  Oxygen. 
657 
continued  addition  of  oxygen  so  long  as  any  of  the  argon 
remained  solid.  Hence,  420  mm.  is  the  total  pressure,  above 
a  saturated  solution  of  argon  in  oxygen  at  82°'09  Abs. 
Since  the  solution  is  saturated,  the  partial  pressure  of  the 
argon  must  be  equal  to  the  vapour-pressure  o£  solid  argon 
at  the  same  temperature.  Hence  the  partial  pressure  of  the 
oxygen  is  (420  —  411)  mm.  =  9*0  mm.  and  the  percentage  of 
411 
argon  in  the  vapour  is   y^  x  100  =  97*8  per  cent.     Several 
samples  of  the  saturated  solution  were  collected  in  the  way 
used  earlier  for  liquid  samples,  and  it  was  found  that  the 
composition  of  the  liquid  remained  constant,  however  the 
amount  of  oxygen  added  might  vary,  so  long  as  there  was 
solid  argon  present.  The  analysis  of  the  samples  showed 
that  the  liquid  contained  92*7  per  cent,  by  vol.  of  argon. 
Hence  we  see  that  the  liquid  containing  92*7  per  cent,  of 
argon  gave  a  vapour  containing  97*8  per  cent,  of  argon  and 
exerted  a  vapour-pressure  =420  mm. 
Table  XI. 
Argon  and  Oxygen.     Temp.  82°*09  Abs. 
No. 
Molec. 
percent- 
Argon 
in 
Liquid. 
Obs. 
Molec.  percent. 
Argon  in  Vapour. 
Total, 
obs. 
Pressure, 
smoothed 
Partial 
Pressure, 
Oxygen. 
Partial 
Pressure, 
Argon. 
Obs. 
0 
5-76 
915 
16-0 
20-6 
Calc. 
1 
2...... 
3 
4 
5 
6 
0 
3-30 
5-6 
10-2 
13-6 
92-7 
Saturated 
0 
97-8 
300-0 
308  2 
310-8 
320-1 
328-7 
420-0 
300-0 
307-5 
312-0 
321-2 
327-5 
420-0 
mm. 
300-0 
290-5 
283-5 
269-8 
2600 
90 
mm. 
00 
17-0 
28-5 
51-4 
675 
411-0 
Since  !the  densities  of  mixtures  of  argon  and  oxygen  at 
82o,09  Abs.  are  not  known,  and  the  density  of  liquid  argon 
at  that  temperature  cannot  be  measured,  one  cannot  plot  the 
pressures  against  the  concentrations.  In  default  of  this, 
the  pressures  may  be  plotted  against  the  molecular  per- 
centages, and  this  has  been  done  in  fig.  3.  The  broken 
lines  in  this  figure  are  drawn  through  the  points  representing 
the  partial  pressures  for  low  concentrations  of  argon  :  and 
it  will  be  noticed  that  they  deviate  considerably  from  the  full 
