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XXXIII. Thermodynamic Properties of Air. 

 By A. W. WlTKOWSKI*. 



[Plates I. & H.] 



Pakt I. 



A. Thermal Expansion of Compressed Air. 



§ 1- AIM of the Work. — It was an important advance in the 

 theory of gaseous matter, when the experimental 

 investigations of Despretz, Pouillet, Rudberg, Regnault, and 

 several others demonstrated the approximate character of 

 the fundamental laws of Boyle and Charles. Instead of a 

 common and single law of compressibility and thermal 

 expansion for different gases, there arose the necessity for 

 determining specific corrections of these laws for every one 

 of them. 



But as soon as the range of temperatures and pressures 

 had been enlarged, new analogies between the physical pro- 

 perties of these bodies became once more evident. First of 

 all, the theory of the critical state may be mentioned here, 

 supported by the discoveries of Andrews, Cailletet, Wrob- 

 lewski, Olszewski, and many others. On the other hand, 

 these analogies found their expression in the laws of compres- 

 sibility, thanks to the investigations of Natterer, Cailletet, 

 Amagat, and Wroblewski. 



At the present time the theory of gases seems to be entering 

 a third phase of its development, initiated by Van der Waals, 

 and supported by Wroblewski, L. Natanson, Ramsay, Young, 

 and many other investigators. There are many facts which 

 seem to show that possibly there may be found, not merely 

 an analogy, but even an identity of properties of different 

 gases, provided that for every one of them special specific 

 units of measure (of temperature, pressure, and density) be 

 employed : all matter seems to be built on the same plan ; 

 but the scale is different for various bodies. 



It is difficult to judge nowadays whether this grand law 

 is an exact truth, or only an approximation : whether it is 

 really universal, or confined only to certain classes of bodies. 

 To confirm or disprove it, numerous and very exact experi- 

 mental data are greatly needed. 



Investigations of the compressibility and thermal expansion 

 in very extended limits prove to be the best means of com- 

 paring the thermodynamic properties of gases : in every case 



* Translated from tlie xxiii. Vol. (1891) of the ' Rozprawy'' of the 

 Cracow Academy of Science (Math. Class), and communicated by the 

 Author. 



