80 



Conductivities and Viscosities in Pure and in Mixed Solvents. 



equilibrium. The percentage transmissions, 1 calculated ratios G/CI, 

 and the constants K,-, are given in table 51. The same values for 

 (I/ 1 )' and (I/ Io)" were used as for the preceding determination. 



SOLUTIONS. 



No. 1. 50 c.c. rosolic acid: 25 c.c. Na 2 HPO,i; 

 No. 2. 50 c.c. rosolic acid; 25 c.c. Na 2 HPO4; 



3 c.c. HC1, diluted to 100 c.c. 

 5 c.c. HC1, diluted to 100 c.c. 



No. 3. 50 c.c. rosolic acid; 25 c.c. Na 2 HPO4; 10 c.c. HC1, diluted to 100 c.c. 

 No. 4. 50 c.c. rosolic acid; 25 c.c. Na 2 HPO 4 ; 15 c.c. HC1, diluted to 100 c.c. 



TABLE 51. 



The values of K,-, table 51, show a steady decrease from 5.65X10 8 

 to 2.89 X 10" 8 , as the solution becomes less alkaline. The average con- 

 stant is 3.91 X 1CT 8 .' 2 The constants were determined on the assump- 

 tion that rosolic acid is monobasic; as is well known, the indicator is 

 dibasic, and the decrease in the constants with decreasing alkalinity was 

 expected. Rosolic acid actually dissociates in two stages according to 

 the equations H 2 In = HIn + H + and HIn = In + H + . 



BEHAVIOR OF ROSOLIC ACID AS A DIBASIC ACID. 



As to the two ions HIn and In, three assumptions can be made: (1) 

 that the intermediate ion HIn is yellow and the secondary ion In is red; 

 (2) that the ionJHIn is red and the ion In is yellow; (3) that both the 

 ions HIn and In are red. In the first case the ratio of the red to the 

 yellow component will be given by 



= TJ T - TT T 



HIn + H 2 In 



: The average values of two determinations are given. 



J The value given by Salm, in Zeit. phys. Chem., 57, 496 (1907), is 1.1 X10~ s . 



