PRIMARY, SECONDARY, 6- TERTIAR Y ALCOHOLS 133 



Whilst, therefore, the distinction between methyl alcohol 

 and the primary, secondary, and tertiary alcohols is more 

 marked, a simple relation appears in the series of primary 

 normal alcohols, since the velocity regularly falls off with 

 increasing distance of the group richest in hydrogen, 

 methyl, and to the extent of 4 per cent, for each inserted 

 methylene group. Here it must be remembered that the 

 velocity of reaction depends, not only on the nature of the 

 reacting body, but on the number of collisions, so that 

 the different rates of diffusion of the alcohols should be 

 considered along with the preceding numbers. It is strik- 

 ing that this varies in a similar manner in other homo- 

 logous series, as appears from the ionic mobilities of the 

 fatty acids l : 



Ionic mobility Quotient 



Acetic acid 43.1 



Propionic acid 39 



Butyric acid 35.5 



Valerianic acid 33.5 



Caproic acid ...... 32-1 



If this influence were taken into account, perhaps all the 

 primary alcohols would have the same velocity of esterifi- 

 cation. 



Velocity of saponification. Let us deal next with the 

 connexion between the velocity constants for esterifica- 

 tion (k^ and saponification (k. 2 ), and the equilibrium con- 

 stant of the reaction K (Part I, p. 203), i. e. the equation 



-' = #. 



This follows immediately from the velocity of formation 

 of the ester 



dCUr _;, r r 



i , 1^1 v alcohol ^acid > 



and the velocity of saponification 



7, 'v-2 Center ^ water 



at 



1 Ostwald, Zeitschr. f. Phys. Chem. 2. 849. 



