6G 



December 10, 1857. 



The LORD WROTTESLEY, President, in the Chair. 



Mr. Robert Angus Smith was admitted into the Society. 



The President announced that he had appointed the following 

 gentlemen Vice -Presidents, viz. Mr. Gassiot, Mr. Grove, Dr. Hooker, 

 Mr. Horner, and Mr. Owen. 



The following communications were read : 



I. " On the Chemical Action of Water on Soluble Salts." By 

 Dr. J. H. GLADSTONE, F.R.S. Received November 19, 185 7. 



Before extending my researches on chemical affinity among sub- 

 stances in solution, it seemed desirable to ascertain, if possible, what 

 specific chemical action water exerts on a salt. This inquiry is beset 

 with unusual difficulties, and unfortunately my experiments have not 

 led to any conclusive result. Yet some of the observations made 

 during the course of the inquiry have a value independent of theory, 

 and a brief notice of them may not perhaps be deemed unworthy of 

 a place in the Proceedings of the Royal Society. 



It is well known that many anhydrous salts will absorb water, and 

 still remain solid bodies, either amorphous or crystallized. In such 

 a case the water combined is always in simple atomic relation with 

 the salt itself ; great heat is often evolved, and a change of colour 

 frequently ensues. These " hydrated" salts (as they are usually 

 considered) are generally soluble in water ; and it is the condition 

 of such a body when dissolved that opens a wide field for speculation. 

 The water may act merely as a solvent ; or it may unite without de- 

 composition with the dissolved salt, becoming an integral part of the 

 compound in solution ; or reciprocal decomposition may ensue, each 

 electro-positive element combining with each electro-negative one in 

 certain proportions ; or the ultimate result may be due to two or more 

 of these modes of action in conjunction. 



When a "hydrated" salt is dissolved in a minimum of water, 



