482 



7 



loop = ^ — + — log r - - C l^dT + C -\- 



') 



2.3 R 







in whicli ?. ineaiis tlie heat of evaporalioii at the temperature T, 

 r, tlie specific iieat of liquid or soHd, r^, the specific heat of the vapour 

 and R tlie gas constant (all for a ^ramnieuiolecule of the substance). 



1 have only made calculations from this formula for the field of 

 solid-vapour. The reason for this will be seen presently. 



The measurements of Dittenberger ") and Pier '') both give the 

 value of 4.91 for the molecular si)eciric heat at constant pressure, 

 of gaseous argon at higher temperatures. As in many cases it has 

 been shown that this qnantity is conspicuously independent of the 

 temperature, we shall make use of it also for low temperatures. 



For R we assume the value 1.985. 



Concerning the value of c nothing is known experimentally. In 

 order to arrive at a rational estimation, in spite of this, of the integral 

 T 



/: 



-dT I calculated the frequency v from Lindemann's ") formula. 



V — 2.80 X I'J'"' 



Mv:i' 



(in which the index refers to the melting point) and then values 

 for c at the various temperatures by the formulae of Nernst- 

 LiNDF,MANN ^) and of Debije"). In the field of temperatui-e with which 

 we have to deal, it makes no difference wdiich of the two formulae 

 we use '). 



Finally the values of the integral were deternjined by the graphic 

 method. 



Naturally these calculations could only be made for solid argon, 

 as Nernst-Lindemann's and Debije's formulae only apply to solid 

 substances. 



1) 1. c. p. 80. 



2) W. Dittenberger, In. Diss, Halle 1897. 



K) M. Pier, Zeitschr. f. Electrochemie 15 (1900) p. 536. 



4) F. A. LiNDEMANN, Pliysik. Zeitschr. 11 (1910) p. G09 and W. Nernst and 

 F. A. LiNDEMANN, Bed. Sitz. Ber. 1911 p. 494. 

 Ó) I.e. 



6) p. Debije, Ann. der Physik. (4) 39 (1912) p. 789. 



7) Tables for the calculation of c are published : for the formula of Nernst- 

 LiNDEMANN by F. PoLLiTZER, Die Berechnung chemischer Alfinitiiten nach dem 

 NERNST'schen Wiirmetheorem, Enke, Stuttgart, 1912, p. 162 sqq; for the formula 

 of Debije by W. Nernsï. Berl. Sitz. Ber. 1912 p. 1172. 



