DILUTION OF CONCENTEATED SOLUTIONS. 



345 



The accuracy with which this can be applied is comparable with that of THOMSEN'S 

 formula in fact the accuracy is greater if the most dilute solution is ignored. 



The equation for heat of dilution now becomes 



dQ_4666 



= ~~ 



Plotting dQ/cZN and 1/N thus gives a straight line which cuts the axis at N = 23'8, 

 which is nearly H 2 S0 4 . 24ILO. (Diagram II.) The suggestion might be made, there- 

 fore, that accepting the linear relation between Q and 1/N, the heats generated were 

 such as if the true solvent were H 2 S0 4 . 24H 2 O instead of pure water. 



(2) Nitric Acid. 



THOMSEN gives six results for Q with solutions diluted down to five molecules of 

 water. 



Taking three of the values 



N = i N = 2'5, 



and 



N = 5, 



the equation derived is 



Q = 2099 log, N-18 N + 3437. 



By reference to the preceding equations the low value of the coefficient of N 

 corresponds to ^ff^ molecules of water in the limiting case where cZQ/dN vanishes. 

 A further equation derived from N = , and N = 5, which assumes the coefficient 

 of N to vanish, gives quite as satisfactory a relation, if allowance for experimental 

 errors is made. 



Here 



Q = 2020 log, N + 3406. 



2 z 2 



