ON SOLUBILITY. 441 



1886 s °h 1D ihty. The sa l ts °f the oxalic acid series were investigated 

 from this point of view by Miczynski. 119 



The solubility of one liquid in another was studied by Alexcjeff, 11 * 

 who found a regular increase in solubility with rise of temperature, 

 provided always that no combination takes place between the two 

 liquids, otherwise no such regularity was observed. He studied more 

 particularly the increase in the mutual solubility of phenol and water 

 as the temperature was raised to the point of complete miscibility. 



1887 Sedlitzky 132 deduced from his own observations mathematical 

 expressions connecting temperature and solubility for various 



salts of iso-valeric, methylethylicacetic and /so-butyric acids. 



A further publication by Etard 12S was in substantiation of his 



1888 som bility formula, and contained constants for copper sulphate 

 solubility graphs. This investigator 137 found that above 103° 



up to 190° the solubilities of most sulphates decrease with rise of 

 temperature; a similar decrease was also observed with salts of carbonic, 

 sulphurous, and succinic acids, but not with salts of monobasic acids, 

 except those of feeble organic acids. 



Roozeboom 13S discussed the influence of temperature on the 

 solubility of double salts, and, in the following year, the solubility of 



1889 hydrated salts in relation to temperature. 140 His conclusions in 

 the latter case were adversely criticised by he Ch atelier, 1 ™ who 



could not agree with hydrated calcium chloride (CaCl 2 , 6H 2 0) having two 

 different coefficients of solubility at the same temperature. When the 

 solubility results were plotted this author found two distinct curves 

 meeting at the melting-point of the hydrate (CaCl 2 , 6H 2 0), one being 

 the solubility curve of the hexahydrate in water, the other that of the 

 anhydrous salt in the solution of hexahydrate. 



The relation between solubility of salts and their melting-points 

 next engaged the attention of Etard, 143 who found with many salts an 

 increasing solubility with rise of temperature up to the melting-point 

 of the anhydrous salt; beyond this point a given quantity of water was 

 considered capable of dissolving an unlimited quantity of salt. Shortly 

 afterwards he obtained similar results 151 calculated from measurements 

 of simultaneous solubility of sodium and potassium chlorides. The sum 

 of the salts dissolved between -20° C. and + 180° C. being represented 



by a straight line Y + ^ = 27-0 + 0-0962i, it was calculated that 



the temperature at the limit of solubility, or limiting temperature — 

 i.e.,. the point where the amount of water has become reduced to zero — 

 is 738°, which is, curiously enough, approximately the melting-point 

 of potassium chloride. A confirmation of this was next published 1S2 

 together with the calculated composition of the salt mixture (NaCl and 

 KC1) at 738°. 



, oq,-) I n a similar manner, 161 calculating from the graphs represent- 



ing the solubility of potassium iodide in water, the limiting tem- 

 perature was found by extrapolation to be 637°, practically the melting- 

 point of potassium iodide (639°). "When potassium bromide is added 

 to the solution of potassium iodide the sum of the two salts in solution 

 is equal to that of pure potassium iodide at the same temperature, and 



