Part VI. 



CONDUCTIVITY AND IONIZATION OF SODIUM HYDROXIDE UP TO 



218 AND OF AMMONIUM HYDROXIDE AND CHLORIDE UP 



TO 156. HYDROLYSIS OF AMMONIUM ACETATE AND 



IONIZATION OF WATER AT 100 AND 156. 



60. OUTLINE OF THE INVESTIGATION. 



The investigation of Noyes and Cooper (Part V) having shown that 

 the hydrolysis of sodium acetate was not great enough at 100 or 156 to 

 permit of the calculation of the ionization of water, we were led to under- 

 take a similar study at these temperatures of ammonium acetate, a salt 

 of a much weaker base whose hydrolysis would therefore be far more 

 considerable. In this case it would be practicable to reduce the hydrolysis 

 by the addition of an excess both of the acid and of the base, since both 

 are only slightly conducting substances; and there would result an 

 increase (instead of decrease) of conductivity corresponding almost exactly 

 to that of the new quantity of ammonium acetate thereby produced out of 

 the free acid and base originally present. As it would, however, hardly 

 be possible in this case to reduce the hydrolysis completely to zero, the 

 equivalent conductance of the unhydrolyzed salt can not be directly meas- 

 ured, and must therefore be regarded as an unknown quantity, but this 

 can be eliminated by making conductivity measurements with different 

 quantities of acid or base added. 



The calculation of the ionization-constant (Kw) of water from the 



hydrolysis (h) of the salt, which is made approximately by the mass- 



hr 



action expression Kw = KaKbtz pr^, involves a knowledge of the ioni- 



(1 hy 



zation-constants (A" A and Kb) of the acid and the base. That of acetic 

 acid at the temperatures in question has already been determined by Noyes 

 and Cooper (section 56, Part V) ; but no data in regard to ammonium 

 hydroxide exist. We therefore first investigated the conductivity of this 

 base at 100 and 156 (making also a few measurements at 51, 75, and 

 125 to assist in applying the temperature corrections) ; and, in addition, 

 in order to obtain the data for calculating with the help of the law of the 

 independent migration of the ions the equivalent conductance A of the 

 completely ionized base, we determined the conductivity of sodium hy- 

 droxide and of ammonium chloride at 100 and 156 at low concentrations 

 (0.002 and 0.012 normal). The measurements with sodium hydroxide 



153 



