AND CALCIUM CARBONATE, ETC., OF WATER SOLUTIONS. 



239 



ascertain whether, in spite of (or rather because of) the variability of the 

 molecular solubilities, the silver salts give constant solubility products or 

 not. As is seen from the tables given below, the extremely interesting 

 result was obtained that, according to Arrhenius's own experiments, the 

 silver salts, whether present alone or with varying amounts of sodium salts 

 with the acid ion in common with them, give rather good constants for 

 the solubility products. 



As the question of the constancy of the solubility or ion product for a 

 difficultly soluble salt is of particular importance in the investigation this 

 paper treats of, space will be taken here to report the calculations made 

 with Arrhenius's data for three of the silver salts, the acetate, which is the 

 most soluble salt studied, the valerate, and the butyrate, which are very 

 much less soluble than the acetate. 



In table 1, giving the solubility of silver acetate at 18.6° in the presence 

 of varying amounts of sodium acetate, column 1 gives the molar concentra- 

 tion of sodium acetate used; column 2 gives the degree of ionization of the 

 sodium acetate in the mixture; column 3 gives the concentration of the 

 ionized sodium acetate; column 4 the total solubility of silver acetate; 

 column 5 the degree of ionization of the silver acetate; column 6 the con- 

 centration of the ionized part of the silver acetate; column 7 the concentra- 

 tion of the non-ionized part, which represents therefore the molecular 

 solubility of the silver salt. Columns 1, 4, 5, 6, 7 are taken from Arrhenius's 

 tables; the degrees of ionization of the sodium acetate as given in column 2 

 were calculated with the aid of the isohydric principle, whose reliability has 

 been amply demonstrated.^ Column 3 is derived from columns 1 and 2. 



For a saturated solution of silver acetate 



CH^COjAg ^ CH3CO/ + Ag- (7) 



the solubility product would be 



CAgXCcH3C0,=K (8) 



in which CcHaCOa represents the total concentration of acetate ions irrespec- 

 tive of their origin from silver or sodium acetate; in each of the experi- 

 ments it is the sum of the values given in a line under columns 3 and 6. The 

 values of the solubility product constant K, as calculated, are given in the 

 last column. 



Table 1. — Silver Acetate. 



1 Noyes, Congress of Arts and Science, St. Louis, vol. iv, p. 318, gives an excellent sum- 

 mary on this question. 



