126 Prof. Kuenen and Mr. Robson on Mixtures with 



considerably higher than those of mixture B at ordinary 

 temperatures ; as the temperature falls in accordance with 

 the previous experiments, the two curves approach each 

 other (fig. 2), and ultimately the pressures of B are higher 

 than those of A. This would naturally have shown even better 

 if we had used the maximum mixture of 45 per cent, ethane 

 instead of 50 per cent. 



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The plaitpoint of mixture A appeared to be at 18°'S5 C. 

 and 60*54 atmospheres, as against 18°*77 C. and 61'3 atmo- 

 spheres obtained before for the same mixture*. The other 

 mixture B had its plaitpoint at 17°*8 C. and 56*17 atmospheres, 

 as compared with 17°"75 C. and 57*2 found before. The 

 temperatures agree very well : the difference in the pressures 

 is due to the uncertainty of the high-pressure gauges used 

 in the earlier experiments, as explained in our paper on the 

 vapour-pressures of carbon dioxide and ethane. 



The two curves (fig. 2) practically coincide for such a long- 

 distance that the exact point of intersection cannot be ascer- 

 tained ; but this is of minor importance. The curve TOMN 

 is the solidification or three-phase curve : starting from T the 

 triple point of carbon dioxide it rises slightly, attains a 

 maximum at 0, and then gradually falls, passing through M, 

 where the curve for the maximum mixture reaches and 

 touches the three-phase curve. From the point of view of 

 the separation of solid carbon dioxide, the mixtures fall into 

 two groups. The mixtures of one group contain less ethane 

 * Phil. Mag. [5] xliv. p. 187. 



