408 Dr. Meyer Wilderman on the Connexion between 



heat of melting, latent heat o£ solution, latent heat of 

 evaporation, &c, and calculate, e. g., solubilities from freezing- 

 points or boiling-points, &c. I shall now proceed to do this 

 in a few cases under the assumption that g, A, I do not vary 

 with temperature, which, however, is never quite the case. 

 I choose for this purpose boric acid and chlorate of potassium, 

 for which the values of g prove to change little with tem- 

 perature. It is evident that better results would be obtained 

 if the variation of g, I, A with temperature were taken into 

 account in the calculation of the same. «" q 



From the equation of the solubility curve "" = -^ and 



J°p = T^we get for the temperature T / (where the solu- 

 bility and freezing-point curves cut each other) and any 

 other temperature T the equation lg tt = „ — o.qrwfl ( T ~" 'T 7 ) 

 for non-electrolytes (I.) and Jg^ = -_T| g _ g-. V) 



for electrolytes (I/) (van't HofFs law). 



In case of electrolytes we shall assume that i remains the 

 same for all concentrations and all temperatures, taking for 

 the same the average of i at T ; and T. In reality this is 

 never the case, but as the values of i vary in more con- 

 centrated solutions only little, and, as far as experiment goes, 

 also not much with the temperature, we may make here this 

 assumption for the sake of simplifying the calculation. 



In Table I. are given the solubilities, freezing-points, 

 and boiling-points observed by Arrhenius, Kaoult, Beckmann, 

 Gerlach ; van't HofFs i's, as obtained from freezing- 

 points and electrical conductivity ; T y and T ///? the points of 

 intersection of the freezing-point and solubility curve, as well 

 as of the solubility and boiling-point curves, as found bv 

 myself or other observers. 



In Table II. the values of g are calculated for boric acid 

 (non-electrolyte) and for C10 3 K (electrolyte) through the 

 whole length of the solubility curve under the assumption 

 that g does not change, or only very little, with temperature. 

 This is pretty well the case with boric acid, and is less the 

 case with potassium chlorate ; the values of q for C10 3 K con- 

 tinuously diminishing with temperature. The value of q calc. 

 falls for potassium chlorate between 0° and 100° from 1019 to 

 9 '4, if the total region from 0° to T° is taken. This drop in 

 the values is naturally still greater when small intervals are 

 successively taken. At higher temperatures the drop in the 



