MOLECULAR VOLUME 



$73 



All these ratios are similar to the ratio of the volumes at 

 absolute zero, and if the compounds differ in composition by a 

 similar constituent, the ratios are likely to form an arithmetical 

 series. Differences in constitution would interfere with this 

 regularity somewhat. 



Such a regularity as the above is very significant, because it 

 indicates what are the ratios of the volumes at absolute zero, 

 which is a condition where atomic vibration is absent. Thus 

 a study of M.V.'s, as ordinarily understood, leads to the detection 

 of constant relations between the combined volumes of the 

 atoms. 



The law which is involved in Relation II. may be called the 

 Laiv of Constant Volume Relations. This relation, while true in 

 principle, may be interfered with by Constitutive Influences to 

 some extent. 



(a) The Law of Constant Volume Relations in the Normal Paraffins 

 under Equally Reduced Pressures 



The ratios are seen to form an approximate arithmetic series, 

 comparing the paraffins with C 8 H, 8 , and C 6 Hi 3 with C 6 H G . Thus 

 in the case of the Molecular Critical Volumes 



CsHig i*ooo C7H 16 1 — 1 x 0*1293 CeH 14 1 - 2 x 0*1255 C5H41 1 — 3 x 0-1225 



P/P K -011795 

 CgHis i'ooo C7HK3 1 — 1 x 0*1218 CeH 14 1 — 2 x 0*1200 CsHi 2 1—3 x 0*1188 



CeH 6 1*000 C6H12 1 + 1 X 0*1208. 



Also, if we compare compounds belonging to the same class, 

 we see that the volumes are nearly in the same ratio as that of 

 the sum of the valencies. This relation must consequently obtain 

 at absolute zero, and represent a constant relation between the 

 volumes of the constituent atoms C and H. 



The ratio holds more accurately the further away from the 



