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LXXXY. The Theory of Molecular Volumes. 

 By Gervaise Le Bas, B.Sc. 



* 



Part II. 



Constitutive Effects in Molecular Volumes. 



(a) The Influence of Homology and the Symmetry of 

 Radicles. 



THIS is a large subject and it permits of only a general 

 treatment in this paper. It is remarkable that whilst 

 laborious attempts have been made to show that molecular 

 volumes are not a distinctively additive property, no one has 

 hitherto attempted to discuss the nature of the constitutive 

 influences operating on the volumes from the point of view 

 of Kopp. 



One of the first which calls for treatment is the effect of 

 the addition of the homologous increment CH 2 . We owe 

 the first recognition of the gradual increase in the differences 

 between two successive terms in a series to Schiff, Lossen & 

 Zander, Gartenmeister, from a study of the aliphatic esters 

 (Annalen, 233. p. 249, 1886), and Dobriner from a study of 

 the ethers (Annalen, 24:3. p. 1, 1886). 



Lossen has subsequently (Annalen, 254. p. 12, 1889) taken 

 up the subject and devised a number of formulae to better 

 account for the volumes of the members of an homologous 

 series. 



Thus for the Formic Esters the formula is 



V, =10-45 (C)„ + 5-225 (H)„ + 10-45 (O) o + 0-25^f^, 



assuming that C = = 211, and also that the increase is 

 rectilinear from Methyl Formate onwards. 



The following formula is based upon a better knowledge 

 of the mode of variation of the atomic volumes, and the 

 assumption is also made that C = 4H, 0' = 2H, 0' = 3H. 



V OT = (6» + 5) {3-645 + (6n-30)x 0-0037}. 



3*645 is the minimum volume of H, viz. at Wt = 35 

 (HC0 2 C 4 H 9 ). 0*0037 is the increment per H equivalent 

 0*0037x6 = 0-0222 for CH 2 . The formula does not apply 

 to the first three compounds as may be seen from the curve. 

 The variation of the atomic volumes is very different from 

 what Lossen supposed, albeit rectilinear, starting from the 

 4th term. 



* Communicated by Prof. W. J. Pope, F.R.S. 



f W represents the number of H equivalents. 



