481 



For practical use in the field of liquid-vapour therefore in our 

 case, Rankine-Bosk's formula is preferable to Nernst's. At the same 



time the following calculation will show that Nernst's formula, 

 also in the field of liquid-vapour is capable of representing the obser- 

 vations as far as the critical [)oint in a fairly satisfactory way, and 

 ill many cases, where the accuracy required is not so very great, 

 may be a convenient help in calculation. I wrote the formula in the 

 more usual form 



logp= - 



A 



4.571. T 



1.75 log T 



4.571 



T+ C 



and took for the chemical constant C in accordance with Sackur ^) 

 the value 0.35, so that there now only remain two constants that 

 are to be determined by the observations. With the value of the 

 constants 



;. = + 1385 and f = + 0.01446 



we get a fairly good correspondence from, the critical point down 

 to the triplepoint, in which the deviations in p are all less than 27o- 



Finally I have tried to calculate all the terms of the formula, 

 which Sackcr deduces from the heat theorem of Nernst, from the 

 available calorimetric data, as Sackur has done for some vapour 

 pressure determinations by Ramsay and Travers -). 



Sackur writes the vapour pressure foi'mula in the following form 



1) 0. Sackur, Ann. d. Physik (4) 40 (1913) p. 80. 



•^) W. Ramsay and M. W. Travers, Phil. Trans. (A) 197 (1901) p. 47. 



31 

 Proceedings Royal Acad. Amsterdam. Vol. XVI. 



