MOLECULAR VOLUME 667 



For another liquid 



V p -V.[i + *'(p)1 



At a higher pressure pi the volumes become 



V o[i + 0(Px)] and V' [i + £'(Px] respectively. 



In the case of normal liquids 



Vq [1 + *(P,)] _ V'o [1 + ^(P 1 )] 

 V [1 + <Mp)] V [i + *'( Pl )] 



V„ [t + 0'(p.)] = Vq [1 + *'(p)] 

 " V [i + *( Pl )J V [i +<£(?)] 



•'. <*>(p) = *'(p) and <f> = 4! 



The function <£ may, however, change towards the critical point. 

 He concludes that: (1) The increase in co-volume is the same 

 function of p for all these liquids, assuming the same law of 

 expansion holds down to the lowest and eventually to zero 

 pressure. 



Vq [I + *'(p)j Vq 



V [1 + </>(p)] v 



(2) The co-volumes V' o 0'(p) and V <£(p) at any pressure are 

 proportional to the actual volumes of the molecules V' and V . 



(3) The ratios between the volumes of the liquids at equal vapour 

 pressures are equal to the ratios between the actual volumes of 

 the molecules. 



These conditions are all that is necessary to justify the 

 investigation of molecular volumes from the point of view of 

 Kopp. This is, however, no proof that the space V</>(p) is 

 actually a molecular vibration space, and can be equally well 

 explained on another assumption. 



(i) In the first place, no account is taken of the vibration of 

 the atoms, which is certainly a fact. The reason it does not do 

 this is owing to a particular conception of the atom which pre- 

 vails, and which tends to regard it as merely a central nucleus 

 which is measured by the Refractivity. Prideaux, like Traube, 

 believes that the vibration space of the atom is the external 

 shell of dielectric, and thus the internal vibrations of the mole- 

 cule are within the space b or V . The central nuclei are 

 spoken of as the atoms themselves, and the shell of bound ether, 

 which is impenetrable to other atoms, is not considered as a 

 fundamental part thereof. 



