Radiometric Measurements of Constants of Indicators. 



61 



The calculations of the hydrolysis and ionization constants are based 

 on logarithmic functions; and where the transmission of the solution is 

 nearly complete, a slight variation from the actual percentage trans- 

 mission will cause a great change in the calculated hydrolysis and ioni- 

 zation constants. If we consider an experimental case where the 

 amount of absorption to be measured is slight, the above can be made 

 quite clear. Solution II in table 32 for wave-length of light X = 5798 

 A. u. actually gave a percentage transmission of 85.6. Changing 

 the percentage transmission by small amounts, and calculating the 

 value of the hydrolysis and ionization constants from these values, we 

 have 



I/Io- 

 85.6 

 86.0 

 86.6 



KIO/K.J. 



6.46X10- 4 

 7.21 X10- 4 

 8.59X10- 4 



1.25X10" 11 found experimentally 



1.12X10- 11 



0.94 X 10- 11 



It will thus be seen that changing the percentage transmission by 

 about 1 per cent will cause a variation in the ionization constant of 

 about 25 per cent. When conditions are not satisfactory, it is quite 

 possible that the error in some of the percentage transmissions may be 

 greater than 1 per cent. Considering these facts, the constants show 

 that the efforts which were made to eliminate errors arising from varia- 

 tions of the current intensity and vibrational disturbances were fairly 

 successful. 



The transmission values given in table 34 are for a much more dilute 

 solution of methyl orange. The concentration of the mother solution 

 of methyl orange was 1.9865X1CT 4 gram-molecules per liter; that 

 of the mother solution of sulphuric acid being 3.0885 X10~ 4 gram- 

 molecules per liter. 



I. 50 c.c. methyl 



II. 50 c.c. methyl 



III. 50 c.c. methyl 



IV. 50 c.c. methyl 

 V. 50 c.c. methyl 



VI. 50 c.c. methyl 



VII. 50 c.c. methyl 



VIII. 50 c.c. methyl 



SOLUTIONS. 



orange, diluted to 100 c.c. 



orange, 10 c.c. sulphuric acid, diluted to 100 c.c. 

 orange, 15 c.c. sulphuric acid, diluted to 100 c.c. 

 orange, 20 c.c. sulphuric acid, diluted to 100 c.c. 

 orange, 1 c.c. cone, sulphuric acid, diluted to 100 c.c. 

 orange, 0.5 c.c. cone, sulphuric acid, diluted to 100 c.c. 

 orange, 0.2 c.c. cone, sulphuric acid, diluted to 100 c.c. 

 orange, 0.5 c.c. cone, sulphuric acid, diluted to 100 c.c. 



TABLE 34. 



[I/I for depth of solution =20 mm.] 



