Section 57. Conductivity Data for Mixtures. 143 



57. CONDUCTIVITY DATA FOR MIXTURES OF SODIUM ACETATE 



AND ACETIC ACID. 



Table 43 gives the results that were obtained with the mixtures of 

 sodium acetate and acetic acid. The values of the conductance are the 

 measured values in reciprocal ohms, multiplied by 10 6 and corrected for 

 the instrumental errors and the lead resistance. The values of the specific 

 conductance were calculated from these by applying the water-correction 

 and multiplying by the conductance-capacity. 



It will be seen that with the 2 and 76 milli-normal salt solutions the ini- 

 tial and final values of the specific conductance agree in every case with- 

 in about 0.1 per cent, and that with the 10 milli-normal solution the two 

 values differ on an average by only 0.2 per cent. This makes it improbable 

 that the results are affected by an error arising from contamination or 

 adsorption. 



58. HYDROLYSIS OF SODIUM ACETATE AND IONIZATION OF WATER. 



The increase in conductance due to hydrolysis of the salt can be derived 

 from the data of table 43 and those obtained with sodium acetate alone 

 (table 35). It is first necessary to subtract from the former values the 

 conductance which the acetic acid itself possesses in the mixture. This 

 can be determined by the application of the mass-action law, which has 

 already been shown to apply to acetic acid at all the temperatures. Accord- 



C Yf 



ing to this law ~ = K. Now Ca c is substantially equal to the con- 



centration of the ionized sodium acetate in the solution, which is readily 



calculated by multiplying its concentration (C s ) by the corresponding 



ionization value (y s ) taken from table 41. The ionization of the acetic 



f 

 acid -^ is then found by dividing its ionization-constant by this pro- 



duct, and its specific conductance (la) is equal to the product of this ion- 

 ization value by the concentration of the acid (Ca) and by its equivalent 



conductance when completely ionized (A oA ), i. e., l a = - . CaA a. 



^ s"Ys 



The specific conductance of the acid is then subtracted from the specific 

 conductance of the mixed solution, whereby the specific conductance of 

 the unhydrolyzed salt is obtained. It is assumed hereby that the acetic 

 acid has been added in sufficient amount to reduce the hydrolysis to a value 

 not differing appreciably from zero; that this was the case was proved 

 experimentally by the addition of varying amounts of acetic acid, and it 

 will also be shown theoretically that even the smallest addition made in our 

 experiments must have sufficed. 



