On the Limit of the Liquid State. 



309 



place. It seems clear then that the temperature at which the perma- 

 nent surface of a fluid (which constitutes liquidness) disappears is not 

 altered by increase of pressure, and this is equivalent to saying that 

 the critical point is the termination of an isothermal line which marks 

 the limit of the liquid state. 



It next remained to be seen whether any other insoluble gas would 

 act in the same manner as hydrogen. It must be remembered that 

 hydrogen is furthest removed from the liquid condition and the least 

 dense body known, and the nearer the density of the superincumbent 

 gas approaches to the density of the liquid, the greater effect will it 

 have upon the critical temperature. To test this, a quantity of 

 nitrogen was placed over alcohol, and the experiment conducted simi- 

 larly to those with hydrogen. 



Table VIII. 

 Alcohol with Nitrogen. 

 Manometer C. 



T. 





T'. 





t 





231 



•5 



232 





78 



79 



232 





231 



•5 



77 



77 



231 



•5 



231 



•5 



78 



78 



232 



•5 



232 





80 



81 



232 





231 



•5 



82 



80 



231 



•5 



232 





80 



80 



232 



•5 



232 





81 



81 



230 





231 





80 



82 



229 





230 





80 



78 



231 



•5 



232 





75 



74 



231 



•5 



231 



"5 



76 



78 



232 



•5 



232 





78 



80 



P. 



t". 



274 



16 



267 



16 



262 



15 5 



262 



15 



270 



15 



270 



15 



276 



16 



276 



17 



276 



18 



278 



17 



277 



16 



273 



15 



Average T 231 50 1 Q orrec ^ed mean temperature 235°11. 

 T'231°-58J v 



Average P 271*75. Corrected mean pressure 82'35 atmos. 



Probable error of mean temperature 0°'22. 

 ,, „ pressure 0*19. 



These numbers plainly show that the meniscus of alcohol disappears 

 at the same temperature, whether under tne pressure of its own 

 vapour or at a pressure of eighty atmospheres with nitrogen, affording 

 further proof that the liquid state terminates at the critical 

 temperature. 



Another method still remained to be tried, that of measuring the 

 capillary height of a liquid under various pressures and temperatures. 

 The method used at first was to fix a small piece of capillary tubing 



