36 Thermodynamic Properties of Air. 



h corresponds to a temperature of about —120°. At ordinary 

 temperatures the temperature- variations of k are exceedingly 

 minute, for all degrees of condensation of the gas. At 

 temperatures approaching the critical the increments of the 

 ratio are the more marked the greater the density ; in the 

 critical state k is infinite. 



With the aid of the diagram (fig. 6) the following table of 

 values of c p : c v has been prepared : — 



1_ 



V 



10. 



20. 



30. 



50. 



60. 



80. 



100. 



9. 







Values of c p : 



c v . 











1-42 



1-43 



1-44 



1-51 



153 



1-55 



1-60 



- 20 



1-42 



143 



1-45 



1-51 



1-53 



1-55 



1-61 



- 40 



1-42 



1-43 



1-46 



1-53 



1*55 



1-57 



1-65 



- 60 



1-42 



1-44 



1-49 



155 



1-58 



1-61 



1-72 



- 80 



1-42 



1-45 



1-50 



1-58 



1-64 



1-69 



1-85 



-100 



144 



1-47 



1-53 



163 



1-71 



1-80 



210 



-120 



1-45 



1-49 



1-56 



1-67 



1-79 



1-92 





-140 



1-38 



1-41 



1-46 



1-50 



1-54 



1-70 



1-80 



Although the general course of the curves of k is very clearly 

 marked, yet some irregularities manifest themselves in the 

 diagram of fig. 6, chiefly at the highest and lowest tempera- 

 tures, where the graphical calculation has been also less 

 certain. I have not attempted to correct them arbitrarily, but 

 I drew the curves as near as possible along the calculated 

 points (marked on the diagram by dots). 



§ 17. In concluding I wish to state expressly that the 

 absolute numerical values of the several thermodynamic 

 quantities given in §§ 12, 14, and 16, being obtained by a 

 graphical method of calculation, cannot claim a degree of 

 exactness comparable with that of direct experimental results.' 

 Notwithstanding this I considered it useful to spare neither 

 time nor trouble to obtain them, in order to throw some lio-ht 

 on these important and wholly unexplored relations. 



During the preparation of the manuscript of the present 

 paper I became acquainted with a memoir of Sgr. Silvio 

 Lussano (Nuovo Cimento, 1894, ser. hi. torn, xxxvi. pp. 1, 70, 

 130 ; 1895, ser. ii. torn, ii., p. 327 ; " Sul calore specifico del 

 gas ") on the influence of pressure and temperature on the 

 specific heat of gases at constant pressure. The results of 

 Sgr. Lussano, being obtained at higher temperatures, are not 



