817 



point, luis been found among- otliei'S by Carooso for dinercnt subslanoes. 



From the above a remarkable relation can .still be derived, namel}^ 



2 



s' — 2 being = z according to (11a), and z being according; to (10) : 



r — 1 



2 



s' —2= , 



r—l 



or as r—l is always =:s: {/' — 6') according to (a): 



s' — 2 = 2'' , 



from which immediately follows: 



2 f =ss' (13) 



Thus e.g. 



Ordinary substance s =^ 3,77 s 

 Argon 3,424 



Ideal substance 2,667 



Here attention must once more be drawn to the difference between 

 s ^= RT/c : pfcVk and .v' = iv, : ij^, which difference is, indeed, small, 

 but never negligible. Thus for an ideal substance .s'' : .y = \/^. The 

 empirical equalisation of .y' and s would only lead to approximate 

 relations (v. d. W.), whereas our above empirical relations are perfectly 

 exact, and seem to hold accurately for all substances. 



6. The found relation between z and r (in (10) ), and in connection 

 with (9) therefore also between r and y — which relation will have 

 to be theoretically justified Iji/ the course of the function b=f{v), 

 through which bk : b^ becomes = 2 y according to (12), which will 

 be discussed presently ^- now enables us in connection with the 

 assumption Aj : ;..^ = 1, to express all the quantities relating to the 

 equation of state in the one independent parameter y. 



In the first place we choose y, because this quantity according to 

 (12) is in the closest relation with the course of the function /; =ƒ(?;), 

 on which after all everything is founded : all the difference between 

 the great diversity of the substances. But in the second place because 

 this quantity y, as said, can be easily experimentally determined, 

 as for this purpose only a number of liquid- and vapour densities 

 must be determined not up to the critical temperature, but near to it. 



From (9) and (10) follows with regard to r : 



2(l + y) 2 



hence 



