330 



ME. W. S. TUCKER ON HEATS OF 



It will be seen that the results derived from his equation lie considerably below 

 those obtained by experiment. 



The discrepancy between THOMSEN'S values and those here obtained does not appear 

 from the value of total heat of dilution quite so obviously. Thus on diluting a 

 solution from HC1 . 2'6H 2 to HC1 . 10ILO, nearly the same quantity of heat appears 

 to be generated. The reason for this is that THOMSEN'S dQ/dJS exceeds the values 

 here obtained for solutions of strength exceeding HC1 . 4H 2 O. 



In order to obtain a measure of the total heat generated, values of dQfdN can be 

 plotted against number of molecules of water per molecule of solute, i.e., the abscissae 

 would read " dilution " instead of concentration. (See Diagram III.) 



16 



18 



2 4 6 8 10 12 4 



Dilution : Molecules of water to 1 molecule of solute. 

 Diagram III. 



The area intercepted between two ordinates separated JN would be ^ N, and 



20 



between limits of concentration Nj and N 2 . 





It will be seen that the curves cross at N = 4, and that the total areas from the two 

 curves are nearly equal. 



The curve connecting heat of dilution and concentration for hydrochloric acid, 

 should, by THOMSEN'S theory, be parabolic. The results of the above experiments show 

 that with concentrations exceeding HC1 . 10H 2 the values lie very nearly on a 

 straight line, which however, for lower concentrations, bends round and approaches 

 the origin. If the straight portion be produced it cuts the axis of concentration at 



