Section 44. Ionization-values. 



ioq 



table 27 considered in connection with those of potassium and sodium 

 chlorides given in table 12 of section 19, Part II. To make these more 

 evident we have brought together in table 28 the values of the percentage 

 ionization as given by the ratio 100A/A for all these substances at a 

 concentration of 0.08 normal. 



Table 28. Percentage ionization (1007) at 0.08 normal. 



It will be seen from this table that the ionization of the three di-ionic 

 salts, sodium and potassium chlorides and silver nitrate, different as they 

 are chemically, have not very far from the same ionization values through- 

 out the whole range of temperature. The same is true of the two tri- 

 ionic salts, potassium sulphate and barium nitrate. Thus the rule already 

 deduced from the ionization values at ordinary temperatures that salts 

 of the same ionic type have roughly the same degree of ionization also 

 applies at high temperatures. 



The principle that the ionization of salts at any definite concentration 

 is smaller, the greater the product of the valences of the constituent 

 ions, is an even more pronounced one at the higher temperatures. Thus 

 at 218 the ionization of the uni-univalent salts in 0.08 normal solution 

 is on the average 74 per cent, that of the unibivalent salts about 50 per 

 cent, and that of the single bibivalent salt investigated only 7 per cent. 



Most striking of all is the fact that the still more definite principle that 

 the un-ionized fraction is directly proportional to the product of the 

 valences of the ions* still holds true approximately when that fraction has 

 become very large as it has at the higher temperatures. Table 29 shows 

 under A the mean values of 100(1 y) at 0.04 molal (and for the uni- 

 univalent salts at 0.08 molal), and under B the ratios of these values to the 

 product (j^v,) of the valences, for the salts of the three types included in 

 table 28. 



*In regard to this, see A. A. Noyes, The Physical Properties of Aqueous Salt 

 Solutions in Relation to the Ionic Theory, Congress of Arts and Science, St. Louis 

 Exposition, 4, 320 (1904) ; Technology Quarterly, 17, 303 (1904) ; abstracted in 

 Z. phys. Chem., 52, 634 (1905). 



