440 REPORTS ON THE STATE OF SCIENCE. 



plotted against temperature intervals, anhydrous salts give straight lines 

 while substances which combine with water do not. 



The trend of such solubility temperature curves was followed beyond 

 the usual temperature of experiment by Tilden and Shenstone," who 

 obtained distinct indication of a relationship between the solubility and 

 the fusibility of substances. 



i QQA Further work by these authors 103 established the fact that the 



rate of increase of solubility at temperatures above 100° follows 

 the order of the melting-points of the substances in question. 



Guthrie 106 made use of these results, supplemented by his own 

 observations, in considering the' question of infinite solubility, and gave 

 experimental evidence for such a state of things as a finite quantity of 

 water dissolving an infinite quantity of salt. He was the first to observe 

 the continuity of the solubility curve up to the melting-point of potassium 

 nitrate. 



Etard 107 determined the solubility of the halogen salts of calcium, 

 strontium, barium, and several other metals between the freezing-points 

 of their solutions and 180°. He found the temperature curves were 

 always straight lines for a certain temperature interval (when solid salt 

 is referred to total liquid and not to water), and he regarded that straight 

 portion as indicating the normal solubility curve. Inflections in such 

 curves were considered as being due to a change of ' state of hydration ' 

 of the salt, and not as representing the true solubility curve. All the 

 salts employed gave solubility values which were proportional to the 

 temperature. 



These conclusions were confirmed in a further publication, 107 in 

 which it w,as stated that in order to describe the solubility of a salt it 

 was sufficient to give a point on the curve of deviation and to express 

 the straight portion of the graph in terms of the equation S = a+bt, in 

 which S — solubility, t = temperature, and a and b are constants. A 

 third communication in the same year supported this opinion and gave 

 constants for various salts. 

 Q . Chancel and Parmentier 109 found the solubility of carbon 



bisulphide in water rapidly diminished as the temperature rose, 

 becoming nil at the boiling-point of carbon bisulphide, the behaviour 

 under change of temperature being that of a substance which forms no 

 chemical combination with the water. 



_ A year later they found 109 that chloroform increased in solu- 



1S85 - bility from 0° to 30°, and decreased from 30° to 55° C. 



The solubility of certain salts in fused sodium nitrate (vide 

 Guthrie (sen.) 10G ) was further investigated by F. B. Guthrie, who 

 found that the higher the temperature the greater the proportion of salt 

 entering into fusion. 



A study of the relation between temperature and solubility of 

 sparingly soluble substances led he Chatelicr 112 to important conclu- 

 sions as to the thermodynamics of solution phenomena (vide Section 

 V. A (ii). 



In the same year Raupenstrauch 113 made a study of the solubility 

 of the silver salts of various acids of the acetic series, and arrived at 

 interesting conclusions regarding the constitution of salts and their 



