Section III, 1917 [35] Trans. R.S.C. 



Contributions to the Knowledge of the Critical Phenomena of Air. 



By J. P. KuENEN AND A. L. Clark, F.R.S.C. 



(Read May Meeting, 1917.) 



The experiments described in the following paper were undertaken 

 to determine the critical data for air more accurately than had been 

 done before, and to study condensation phenomena in the critical 

 region. The work of Wroblewski,^ Olzewski^ and Witkowski^ left 

 much to be desired as regards accuracy, and since their determinations 

 were made, the theory of mixtures has been developed and many 

 facts regarding the behaviour of mixtures in and near the critical 

 region have been discovered*. 



It was hoped that some of the interesting phenomena of mixtures 

 near the plait-point temperature^ might be observed with air, and that 

 data for condensation phenomena below this temperature might be 

 obtained. All of these hopes have been realized, even to the observa- 

 tion of retrograde condensation^, which seems never to have been 

 seen at such a low temperature before. 



Of course water vapor and carbon dioxide must be removed from 

 air which is to be subjected to the low temperature of the critical 

 region and in all experiments of the nature of those described below, 

 air is understood to be ordinary atmospheric air with these two gases 

 removed. While air is then a ternary mixture of nitrogen, oxygen 

 and argon, the amount of argon present is so small and its properties 

 are so like those of the other components, that we may regard air 

 roughly, as a binary mixture. 



■ We were fortunate in being able to avail ourselves of the equip- 

 ment and organization of the Leiden laboratory, and much of the ap- 

 paratus and technique have been described in previous numbers of the 

 communications from that laboratory.^ The method employed was 

 similar to that used by Witkowski, and consisted in compressing air 



' Wroblewski, Ueber das Verhalten der fliissigen atmosphasrischn Luft. Wied. 

 Ann. 26, 134, 1885. 



* Olzewski Comptes Rendus, 99, 184, 1884. 



2 Witkowski, Thermodynamic Properties of Air. Phil. Mag., S. 5. 41, 1896. 



* Kuenen, Verdampfung und Verflussigung von Gemischen. 

 ^ Kuenen loc. cit. p. 59. 



* Kuenen loc. cit. p. 60. 



^ References are to Communication from Physical laboratory of University of 

 Leiden. 



