u6 Conductivity of Aqueous Solutions. Part V. 



of its neutral salt) evidently corresponds to the difference between the 

 conductivity of the sodium hydroxide that exists free in the original solu- 

 tion and that of an equivalent quantity of sodium acetate. From the so- 

 derived degree of hydrolysis and the ionization-constant of the acetic 

 acid, the ionization-constant of water itself can be calculated with the 

 help of the mass-action law, as has been shown by Arrhenius.* 



The determination of the hydrolysis of the single salt, sodium acetate, 

 and the calculation from it of the ionization of water at any temperature 

 involves, therefore, conductivity measurements of solutions at various 

 concentrations of the following substances: (1) sodium acetate alone; 

 (2) sodium acetate mixed with acetic acid (preferably in varying pro- 

 portions) ; (3) acetic acid; (4) hydrochloric acid; (5) sodium chloride 

 in very dilute solution (the last two being necessary in order to compute 

 the conductivity of completely ionized acetic acid according to the rela- 

 tion A (ha C ) = A 0( NaA C ) +A(hcd A 0( NaCn; and (6) sodium hydroxide 

 in dilute solution. These measurements, except those with sodium hy- 

 droxide, have been made at a series of four temperatures, 18, 100, 156, 

 and 218, by one of us ( H. C. Cooper ), those with sodium chloride at 

 218 being, in part, however, a repetition of the earlier ones of Noyes and 

 Coolidge. Measurements with sodium hydroxide at the same tempera- 

 tures have been made in this laboratory by Mr. Yogoro Kato ; and these 

 will be described in Part VI. All the data necessary for the calculations 

 are therefore available. 



Since the measurements with hydrochloric acid and acetic acid are the 

 first ones made with acids at high temperatures, and since those with 

 sodium acetate make possible a comparison of the behavior of this or- 

 ganic salt with that of the inorganic salts previously investigated, the re- 

 sults have a considerable interest of their own; and a large part of this 

 article is devoted to the presentation and discussion of them. 



Before considering these results, however, the apparatus and method 

 used for the conductivity measurements and the preparation and stand- 

 ardization of the solutions must be described ; and to this description the 

 next two sections will be devoted. 



47. APPARATUS AND METHOD OF PROCEDURE. 

 The apparatus used was substantially the same as that employed in the 

 previous investigation of Noyes and Coolidge. (See Part II.) Only 

 the small modifications made in it will be here described in detail. 



THE CONDUCTIVITY CELL, OR BOMB. 



The bomb itself was the same one that was used by these investigators. 

 It was used without any modification in the first experiments. Somewhat 



*Ztschr. phys. Chem., 5, 17 (1890). 



