10 Mr. W. Sutherland on Ionization in Solutions 



Walden's data. For N(C 2 H 5 ) 4 I in acetic anhydride he esti- 

 mates, by empirical and graphic methods, the value o£ X at 

 2.5° to be 74*5 with which he calculates X//V from his experi- 

 mental values o£ X at the different dilutions given below. I 

 find that his values of X/X can be represented by X /X = S 908 

 + 34 , 3« 5 " as is shown by the comparison : 



1/10% 



1 



2 



d 



8 



16 



32 



1000A/A exp. ... 



594 



, 669 



733 



788 



832 



864 



,, calc. ... 



607 



669 



728 



782 



832 



879 



The differences are within the range o£ experimental error 

 shown in Walden's measurements. It is to be noted that the 

 0*908 of our formula ought to be 1*0. This shows that 

 Walden's empirical and graphical estimate of X is about 

 10 per cent, too small. It ought to have been 82 instead of 

 74-5. The theoretical equations (13) and (14) enable X to 

 be found from measured values of X. With X = 82 the 

 formula for these experiments becomes X/X = l + 37'8«3. In 

 our second example relating to N(CoH 5 ) 4 I dissolved in 

 ethyl alcohol, we shall go direct to the experimental data of 

 Walden and deduce both X and the coefficient of nl-in (14). 

 Thus I find X = 81'9 instead of 60 as given by Walden, and 

 then X /\ = l-f- 7 3 n~3 with the following comparison: 



1/10 3 ;* .. 



30 



64 



128 



256 



512 



1024 



20-18 



X exp 



.. 24-49 



28-87 



34-08 



38-90 



43-18 



46-60 



49-05 



X calc 



.. 24-49 



29-88 



33-48 



38-15 



42-88 



47-54 



52-04 



The agreement is again within the limits of experimental 

 error shown in Walden's data. 



The next verification of the theory is contained in the 

 instalment of his work which Walden has devoted to the 

 connexion between X and r] (Zeitsch. f. pliys. Chem. lv. 190B, 

 p. 207). For solutions of N(C 3 H 5 ) 4 I in 29 organic solvents 

 he finds that at 25° X ?7 ranges from 0*595 to 0*860, with a 

 mean value 0*70, though tj q ranges from 0*00316 for acetone 

 to 0*08 for benzoyl-acetic-ethylester. Glycol gives a value 

 1*32 and water a value 1*00. According to (8) and (11), for 

 a given solute in different solvents X ?; ought to be constant. 

 For Walden's 29 solvents the average departure of \'r) Q from 

 0'700 is 0*037. The general verification of the constancy of 

 XoVo required by (11) is fairly satisfactory. But we have 

 seen that Waldeir's values of X are liable to considerable 

 error through being estimated graphically and by an empirical 

 formula. 8o I have used his experimental data to find the 



