and flic Equilibrium Constants of Chemical Reactions, etc. 473 



temperature T" is obtained, at which the solubility of B is equal to 

 that of A at the temperature T. In this way the solubilities of B 

 covering the range of known solubilities of A can be calculated. 



I have tested this method in the case of a considerable number of 

 substances of very varied character and solubility, and have, in all 

 cases, found a very satisfactory agreement between the values of the 

 solubility as calculated by means of the above method and those deter- 

 mined experimentally. This is readily apparent from Tables II, III, 

 IV, and V. 



In the following tables the solubilities are expressed in gramme- 

 molecules of substance in 100 gramme-molecules of solvent (water). 

 With regard to the solubilities of zinc chloride and bromide, and of 

 cadmium bromide, the values obtained by li. Dietz* were employed. 

 In the case of the other salts, the solubilities of potassium chloride 

 and bromide were determined by de Coppet ;f those of potassium 

 nitrate by Andrea, \ and those of the oxy-benzoic acids by Walker and 

 Wood. The values of R, or the ratio T/T' are calculated by means 

 of the temperatures marked with an asterisk. 



Table II. ZnBr,, and ZnCl,.ILO. 

 r = 0-00316. 



As can be seen from the above table, the solubility of the zinc 

 bromide changes much less rapidly with the temperature than that of 

 zinc chloride. Since the solubility curve of zinc chloride is rather 

 steep, a comparatively small error in the temperature gives a com- 

 paratively large error in the calculated value of the solubility. The 

 agreement, nevertheless, between the calculated and the determined 

 values of the solubility is very satisfactory. 



* ' Wissensehaf tliche Abhandlungen der Physikalisch-techniachen Keiohaan- 

 stalt'; and ' Berichte D. Chem. G- ,' 1899, vol. 32, p. 90. 



t ' Ann. de Chimie ' [5], vol. 30, p. 414. 



J ' Jl. Prakt. Chem.,' vol. 137, p. 474. 



' Trans. Chem. Soc.,' 1898, vol. 73, p. 618. 



