264 



Conductivity of Aqueous Solutions. Part VIII. 



his, the difference being 5.5 per cent at 0.2 milli-molal. This divergence 

 is doubtless largely due to the fact that Foster subtracted the conductance 

 of the water, which in this case amounted to 3.6 per cent of the whole 

 conductance. The values for nitric acid in the dilute solutions are in 

 excellent agreement with those of Goodwin and Haskell, who used a 

 special method to eliminate the effect of impurities in the water. For the 

 stronger solutions, our values exceed Kohlrausch's by about 1 per cent; 

 but here, as for sulphuric acid, our value was checked (on May 11, 190G) 

 by an independent measurement of a 100 milli-normal solution in a 

 U-shaped vessel, whereby the value 346.8 (instead of 346.4) was obtained. 



96. CHANGE OF THE EQUIVALENT CONDUCTANCE WITH THE CON- 

 CENTRATION AND THE TEMPERATURE. 



As in the previous researches in this series we have determined what 

 value of n must be used in the equation C(A A)= K{Ch.) n to make 

 it conform to the results. The values of the exponent so obtained are 

 given in table 111. 



Table 111. Values of the exponent n in the function 

 C(A A)=K(CA)n 



The values of the exponent at 260 and 306 for hydrochloric acid 

 were found to be 1.35 and 1.60, respectively, while Noyes and Cooper's 

 values (see table 39, Part V) at the lower temperatures range from 1.38 

 to 1.47. For sulphuric acid at 18 (up to 50 milli-normal) the exponent 

 has the value of 1.5; it was not determined at the higher temperatures 

 because the ionization-relations are there complicated by the presence in 

 large quantity of the intermediate HS0 4 ~ ion. It will be seen from these 

 results that the conductance of nitric acid and hydrochloric acid changes 

 with the concentration according to the same law as does that of the 

 neutral salts; and that the same is true of the tri-ionic base barium 

 hydroxide and of the tri-ionic acid sulphuric acid at 18. The insignifi- 

 cant variation of the exponent with the temperature in the case of all 

 these substances is also worthy of notice. It is of interest, too, to note 

 that the exponent for phosphoric acid, which is only moderately ionized, 

 is intermediate between that found for the largely ionized substances and 

 that required by the mass-action law. 



