32 ELECTRIC CHARGE ON NATURAL SOLUBLE 



and the use of this notation simplifies both calculations and the 

 construction of the graph. In Fig. 4, the abscissae are the 

 hydrion exponents, P H , while the ordinates are the values of p, 

 the undissociated fraction. As the highest value 'of the con- 

 centration of neutral particles (x) is when this coincides with 

 the total concentration of the dissolved substance, the maximum 

 value of p is i. For this value all the particles are electrically 

 neutral, and the dissociation is nil. 



It is clear that for amphoteric electrolytes with the same 

 value of the product K a . K b , the p P H curves will be identical ; 

 only the position of the curves will be displaced to the left 



1' 



zr\ 









01 











1 



3 56 7 8 9 10 11 1% 13 W 



FIG. 4. Curves of the undissociated fraction (/u) for K. w = i'io X io-!4. 



with increasing K a , and to the right with increasing K 6 . Curves 

 II. and V. are those for amphoteric electrolytes with product 

 K a . K & = io- 16 . In curve II. K a = K ft = io~ 8 , while in 

 curve V. K a = io~ 3 and K 6 = io- 13 . The maximum propor- 

 tion of neutral particles, i.e., the iso-electric point, is in the first 

 case (II.) at P H = 7 (C H = io~ 7 ), and in the second case (V.) the 

 increase in K a shifts it to the left at P H = 2. 



The dependence of the form of the curve on the value of the 

 product K a . K& is clearly seen in curves I. IV. 



I. K a = K 6 = io- 7 



II. K a = K 6 - io- 8 



III. K fl = K 6 = io- 9 



IV. K a = K 6 = io- 11 



KT7" 

 a r^b 



_ -14 



K b = io- 16 

 K b = io- 18 

 K 6 = io- 22 



K a /K 6 is constant for curves I. to IV. and P H has thus the 



