1880.] 



On the Solubility of Solids in Gases. 



487 



many eminent workers in the field. It would lead to the result that the 

 boiling point of a homogeneous liquid would vary with the amount of 

 space over the liquid, and that the vapour tensions of liquids as deter- 

 mined by placing some over the mercury in a barometer, would vary 

 with the amount of liquid used. This no doubt would be true of 

 a mixed liquid whose constituents have different boiling points, but 

 cannot be said of a homogeneous liquid. I had often noticed that 

 the critical point of a carefully dried liquefied gas was the same whether 

 observed at the top of the tube or at the bottom ; but any impurity or 

 moisture would cause the critical point observed at the bottom to be 

 high, as it would be concentrated in the last portions of the liquid. 

 Since Dr. Ramsay's paper was published I have again gone over this 

 ground, and to prevent mistake I used the same liquid in the same 

 tube, varying its volume so as to make the disappearance of the 

 division take place near the top or bottom of the tube ; and I here give 

 a series with alcohol and carbon dioxide with the results. 





Alcohol. 



Carbon 



dioxide. 



Top. 



Bottom. 



Top. 



Bottom. 



234-5 



234-1 . . 



31-2 . . 



30-9 



234-0 



234-7 . . 



31-0 . . 



. . 313 



235-0 



234-5 . . 



. 307 . . 



31-2 



234-2 



233 9 . . 



30-8 . . 



. . 30-7 



234-8 



234-3 . . . 



311 . . 



. . 30-8 



In these experiments every precaution was taken in purifying the 

 substances, but the bath used was the old double one, otherwise 

 closer observations might have been made. They prove exactly what 

 was known before, and what Dr. Ramsay denies, that a homogeneous 

 liquid has a fixed boiling point, whether that be the absolute boiling 

 point (critical point) or a lower one. I find that liquefied gases give 

 the best results to illustrate this, as they are more easily obtained pure 

 and dry. I have tried ammonia and sulphur dioxide with the same 

 results. Several ethers, especially oxalate of ethyl and methyl, failed 

 to give the same temperature at top and bottom, a difference of 

 several degrees often occurring. This, I have no hesitation in saying, 

 is due to impurity or to alteration of the liquid at the elevated tem- 

 perature. It is difficult to conceive how it could be imagined that the 

 ratio of a homogeneous liquid to the size of the vessel containing it 

 could influence the tension or density of its vapour. As experiment 

 and theory point to the fact that at the same temperature the vapour 

 of the same liquid must have the same tension and density, irrespective 

 of the size of the containing vessel. 



In another place, Dr. Ramsay says : — " From the first experiment 

 it is seen that, on cooling, the liquid contracts more rapidly than the 

 gas." In another, " Whereas, even above their critical points, liquids 



