412 Dr. Meyer Wilderman on the Connexion between 



the dissolved solid, continuously stirring the solution and 

 separating the dissolved substance during this. The 

 cooling and stirring are continued until, in the presence 

 of an ice-crystal, the saturated solution begins to separate 

 ice. The ice is then melted and the experiment repeated 

 more carefully, the point of the first formation of ice being 

 carefully watched. 



In the case of electrolytes the value of i / belonging to T y ought 

 to be known, but it can, for our purpose, be assumed to be equal 

 to (i) at any other point on the freezing-point curve not very far 

 removed from T r For non-electrolytes, where the laws of os- 

 motic pressure directly hold good- the molecular freezing-point 

 depression is, for one and the same soh r ent, the same for all 



T — T /7 (C) 



dissolved substances, i. e. °. ri — or ^ ^ f|v/ is constant, and 



(y) ly— 1 



™ 4t>= fo^f f°i* water, M being the molecular weight of 



the dissolved substance, therefore for any lg (( ')) — lg (T — T") 



M 



we may put a constant lg — — t ? and we get instead of (A) : 



i ff o- -? fl ^ • M 



m$-i)+ i *^y+ 1 *-m''P 



2x2-3026 

 for all non-electrolvtes in water, &c. 



Thus it is enough, in the case of non-electrolytes, to know the 

 temperature (T,) at which the saturated solution of the substance 

 freezes in tlie presence of an excess of the same, and the heat of 

 solution of the substance in the given solvent (q), to be able to 

 calculate its ichole solubility curve*. In case of electrolytes the 

 additional knowledge of van 3 1 Hoff's i is necessary. 



In Table III. the solubilities are calculated from freezing- 

 points for boric acid (non-electrolyte) and potassium chlorate 

 (electrolyte). For boric acid the results are also given, 



when lg ToT^ instead of the observed lg(G)— lg(T — T") is 



taken. Considering that the values of q and \ were assumed 

 to be independent of temperature, and that the solubilities at 

 higher temperatures are for reasons indicated before not very 

 correct, the obtained results are certainly as good as we could 

 possibly expect them to be. 



Again, from the equation for the boiling-point curve 



C = 9 m /g l° r non-electrolytes and C = v 9 .m /a 



for electrolytes, we get for the point of cutting T //y and any 

 other temperature T" between T ' and T ///5 if we assume that 



