294 



Messrs Laby and Carse, On a relation, etc. 



In finding data for the table we have been restricted by the 

 considerations that the ionic volumes may not be legitimately 

 deduced for substances, which are gaseous (e.g. methylamine), or 

 solid (e.g. morphine, oxalic acid), at the ordinary temperature, 

 nor may substances whose densities have been determined only at 

 temperatures considerably removed from the range 15° — 20° C. be 

 used. We propose, however, to attempt to obtain these ionic 

 volumes later by indirect methods. Having regard to the above, 

 all the values for ionic volumes that have been obtained for 

 organic acids and bases are included in the table. (Considerable 

 difficulties are met with in finding comparable values for the 

 inorganic ions.) 



Benzylamine from its preparation and properties — an am- 

 moniacal liquid not forming diazonium compounds — would be 

 classed with the primary fatty amines ; from its graphical formula 

 with the anilines. In the table it is put with both. 



Discussion of Table. 



The last three columns of the table show that the velocity of 

 the ion of a member of a homologous series of the organic acids 

 and bases examined varies inversely as the cube root of its volume, 

 for the product of these is sensibly constant. Thus there is con- 

 siderable evidence that for a homologous series the velocity of an 

 ion is inversely proportional to its linear dimensions. The average 

 value of the product, ionic velocity x cube root of ionic volume, for 

 the acetic* — ?i-caproic acid series is 151, for the pyridines 202, for 

 the amines 186, for the anilines 177. Thus, for ions of the same 

 linear dimensions (cube root of ionic volume), the chemical properties 

 influence their velocities as is shown by the following table in 

 which the ions have closely the same volume. 





Ionic volume 



(Ionic vol.)i 



Ionic velocity 



Product 



A w-Caproic acid . 



1197 



4-93) 



3-01 



148v 



B Ethyl pyridine 



119-7 



4-93 



4-05 



•200 \ 



G Isoamylamine . 



121-5 



4-95i 



3-73 



(185 J 



a n- Valeric acid . 



102-9 



4-69) 



3-17 



\ 149 7 



b a-Picoline . 



105-1 



4-72 



4-30 



^203 



c Isobutylamine . 



1048 



4-71 > 



3-99 



188 



* The value 179 for this product in the case of the formic acid anion is not 

 surprising as this anion does not contain a CH 3 group, and so the shape of the ion 

 (see later) is unlike that of the remaining members of this series. 



