MOLECULAR VOLUME 675 



The results show that the series is an additive one under the 

 various conditions, a fact which agrees with the arrangement of 

 the substances in series. It follows that the volumes of the 

 atoms maintain their relative values under the different con- 

 ditions. This is because the changing physical conditions affect 

 the atoms Sn and Pb similarly — that is, change of temperature, 

 and, what is more important, change of state. 



C 



The symbolical relations previously given enable us to arrive 

 at a third regularity, which is suggested by the above tables. 

 We have seen that 



** P" = P = const - t 1 + ^ p) l 



which suggests unchanging internal volume relations because 



V. V^ Sn'(V a ), 

 V m V 2n(V a ) * 



We also see that since 



5 s = S* - [1 + *(p>] 



* o * o 



2n(V a ) a 2n'(V a ) L + 9WJ 



and (V a ) p = (V a ) [1 + *(p)]. 



At any pressure p, we have thus to do with a number of atomic 

 vibration volumes, which bear the same relation to each other 

 as their volumes do at absolute zero ; for if (V' a ) p and (V a ) p be 

 two combined atoms at pressure p, 



(V.) P (V a )o[i + <Mp)] = (va 



(V.) p (V a ) [1 + 0(p)] (V.). 



For the above reason the investigation of molecular volumes 

 from the point of view of Kopp is justified. 



The Third Regularity is the Law of Additive and Constitutive 

 Relations in molecular volumes. The investigation is possible, 

 because we choose conditions such that the molecular volumes 

 are equimultiples of the volumes at absolute zero, or the real 

 molecular volumes. 



'In accordance with the above ideas, we note the unchanging 

 relation which exists between the volumes of C and H, viz. 



