no CARNEGIE INSTITUTION OF WASHINGTON. 



and still larger for those of the bi-bivalent type : (3) that different 

 salts of the same type have roughly the same degree of dissociation 

 at high temperatures, just as they do at ordinary temperatures ; 

 and (4) that the migration-velocities of different ions approach 

 equality with rising temperature. The conductivity of magnesium 

 sulphate passes through a maximum between 130° and 155°, show- 

 ing that in this case the decrease in dissociation is great enough to 

 compensate the increase in migration velocitj'. 



The second research, upon the hydrolysis of salts at high temper- 

 atures, has thus far been confined to one salt, sodium acetate, at 

 temperatures extending up to 218°. The determination of the hy- 

 drolysis of this salt involved, however, not only measurements of its 

 own conductivity at various concentrations, but also those of solu- 

 tions of acetic acid, hydrochloric acid, and sodium hydroxide. The 

 method in principle consists in determining the decrease in conduc- 

 tivity of sodium acetate produced bj' the addition of acetic acid to 

 its solution. This decrease arises from the driving back of the hy- 

 drolysis of the salt by the excess of acid and the replacement of 

 sodium hydroxide by a corresponding quantity of the more poorly 

 conducting sodium acetate. The final calculations have not j'et been 

 made ; but the results show that this salt, which at 25° in y-J-Q nor- 

 mal solution is hydrolyzed to an extent of only about 0.03 per cent., 

 at 218° has a degree of hydrolysis of about 0.5 percent. From the 

 data the degree of dissociation of water itself will be calculated ; 

 these results already show that it is many times greater at 218° than 

 at 18°. At high temperatures the phenomenon of hydrolysis there- 

 fore plays a most important part in determining the condition of 

 salts in solution. The conductivity measurements incidentally made 

 with hydrochloric and acetic acids have also an interest of their own; 

 they show that the dissociation of both these acids, like that of the 

 neutral salts, decreases markedly with rising temperature. 



The third research consisted of about forty electrical transference 

 experiments at 20° with very dilute hydrochloric and nitric acids. 

 The object of them was to determine the electrical conductivity of 

 the hj^drogen ion — a constant of fundamental importance in appli- 

 cations of the ionic theory, since it is involved in the calculation of 

 the degree of dissociation of all acids. The transference numbers 

 obtained with -5^ normal hj^drochloric acid are nearly identical 

 with those previously obtained with j^-^ and y|-o normal acid by 

 Noyes & Sammet.* They therefore confirm the conclusion pre- 



*J. Am. Chem. Soc, 24, 944 (1902) ; ^5, 165 (1903). 



