1883.] Solubility of Salts in Water at High Temperatures. 345- 



IX. "On the Solubility of Salts in Water at High Temperatures.'' 

 By William A. Tilden, D.Sc. LoncL, F.R.S., Professor of 

 Chemistry in the Mason Science College, Birmingham, and 

 W. A. Shenstone, F.T.C., F.C.S., Lecturer on Chemistry in 

 Clifton College, Bristol. Received June 19, 1883. 



(Abstract.) 



This paper contains an account of experiments made with the view 

 of determining the solubility of salts in water at temperatures above 

 the boiling point of water. They were originally undertaken with the 

 object of further investigating the anomalies presented by sulphate of 

 soda, but the method adopted was afterwards applied to many other 

 metallic salts, and the paper presents an account of determinations so- 

 made, together with a discussion of the theoretical bearing of the 

 results. 



The main conclusion arrived at is that solubility is directly related 

 to fusibility. Of the salts operated upon some habitually crystallise 

 with water of crystallisation, others habitually in the anhydrous state. 

 When the latter are written down in the order of their melting points, 

 beginning with the most fusible, it is observed that increase of 

 solubility consequent upon a given rise of temperature above 100° 0., 

 is greatest in the most fusible, least in the least fusible, and all the 

 cases observed follow this rule in regular order. If the results are- 

 represented graphically, taking for abscissas the degrees of tempera- 

 ture and for ordinates the quantity of salt dissolved in 100 parts of 

 water, it is at once seen that the higher the melting point the more- 

 nearly do the curves so constructed approach a straight line. The 

 relation is illustrated by the case of the chloride, bromide, and iodide 

 of potassium, the solubilities of which at all observed temperatures 

 follow the order of the melting points. Also in comparing together 

 two such salts as chlorate and chloride of potassium, the solubilities and 

 melting points of which are as follows, the curves cutting each other 

 at 100° :— 





Melting 

 point. 



Solubility at 



0°. 



100°. 



130°. 



• 



180°. 





359° 

 734° 



3 3 

 29-2 



Si 



88-5 

 66 



190 

 78 







As to sulphate of sodium the solubility increases as the temperature 



