G04 



Mr. E. Vanstone on the 



It is obvious that the variation in the values of 



M 



W 



are- 



due to the great variations in ™ more than to changes in. 

 the specific volume. 



We are therefore forced to the conclusion that the use of 

 the so-called stere (obtained by finding the value of the ratio 



V \ 



^ J for tracing changes in constitution is likely to lead to 



false conclusions. 



The following extract is taken from Le Bas (Phil. Mag. 

 1907, xiv. p. 336): — "Assuming that the 4 : 1 rule applies 

 very closely between the atoms of any individual hydrocarbon 



V 



under all physical changes, the ratios ^ not only show the 



validity of the above rule for the different members of a 

 series under corresponding conditions, but they also show 

 the extent of constitutive changes from compound to, 

 compound." 



The argument used above applies in all cases, whether the 

 molecular volumes are found at the critical temperatures,, 

 equall}' reduced temperatures, melting-points or boiling- 

 points. 



The case of the olefine series is particularly interesting, 

 for the molecular weight of the first member is a multiple 

 of 14; hence the molecular weight of any member = 14 n y 

 where n = number of CH 2 groups in the compound. Also the 



M 



sum of the valencies = 6 n. Hence the second factor 



W 



in the Le Bas ratio is an absolute constant for all olefin es, 

 whether they are low or high members of the series. The 



value of the constant = -^ = 2 3- Tne value o£ the stere of 

 o n — 



Le Bas = v x 2 j -. 



Le Bas has shown that this is constant, hence the specific 

 volumes must be constant, as in the case of the paraffins.. 

 This is shown to be so in the table below. 



defines at M.Pt. 



V. 



v. 



1-2572 

 1-2597 

 1-2631 



1-2642 



M 



W* 



2-333 

 2-333 

 2-333 

 2-333 



V 

 W" 



Dodecyleue, C 12 H 24 ... 

 Tetradecylene,Cj H 28 ... 

 Hexadecylene, C 16 K 3 l .. . 

 Oetadecylene, 18 H 36 ... 



211-21 

 246-90 

 282-94 



31858 



2-933 

 2-939 

 2-947 

 2 949 



