Royal Society. 185 



states of combination as basic and saline water. Thus the hydrate 

 of sulphuric acid, already mentioned, contains one equivalent of 

 basic, and one equivalent of saline water. It is, in his nomencla- 

 ture, a sidphate of water with saline ivater, as the hydrous sulphate of 

 zinc is a sulphate of zinc ivith saline ivater. The bi-sulphate of potassa 

 is also a sulphate of ivater tvith sulphate of potassa, and corresponds 

 with the double salt of sulphate of zinc with sulphate of potassa. 



The results which Professor Graham has thus obtained, and which 

 he has communicated, partly to the Royal Society, and partly to 

 the Royal Society of Edinburgh, suggested to him the probability 

 that the law with respect to water in the constitution of the sul- 

 phates would extend to any hydrated acid, and the magnesian salt 

 of that acid ; and his researches on this extension of the subject 

 constitute the substance of his last communication to the Royal So- 

 ciety. As he had already found that the sulphate of water is con- 

 stituted like the sulphate of magnesia, so he now finds oxalate of 

 water to resemble the oxalate of magnesia, and the nitrate of water 

 to resemble the nitrate of magnesia. He is moreover of opinion, that 

 this coi-respondence between water and the magnesian class of ox- 

 ides extends beyond their character as bases, and that, in certain 

 subsalts of this class, the metallic oxide replaces the water of cry- 

 stallization of the neutral salt, and discharges a function which was 

 thought peculiar to water. 



The same kind of displacement, which takes place in the forma- 

 tion of a double sulphate by the substitution of a salt of the same 

 class for an equivalent of water, appears to occur likewise in the 

 constitution of double oxalates ; and the application of this princi- 

 ple elucidates the constitution of that class of salts, as well as of the 

 super-oxalates, and explains the mode in which they are derived. 



Lastly, the same law is traced in the constitution of the chlorides 

 of the magnesian class of metals, which are found to have two equi- 

 valents of water strongly attached to them, and which may therefore 

 be considered as constitutional. Many of them have two or four 

 equivalents more, the proportion advancing by multiples of two 

 equivalents. 



Professor Gi'aham has supported these views, not only by nume- 

 rous arguments, but also by experimental investigations of the phj^- 

 sical properties of different classes of salts, and a great number of 

 chemical analyses ; and he has thus lai'gely added to our positive 

 knowledge of this somewiiat neglected branch of chemical science. 



Thc' Council, without pronouncing any judgement on the ques- 

 tion whether Professor Graham's hypothesis concerning the differ- 

 ent functions of water in the constitution of salts be a representa- 

 tion of the real mechanism of nature, are of opinion, that the dis- 

 cussion of his new and ingenious views will be highly conducive to 

 tlie progress of science, particularly in the department of organic 

 chemistry, in which they iiave been already followed out with suc- 

 c(!ss by some eminc^nt foreign chemists, and have accordingly awarded 

 to Professor Graham the Royal Medal for Chemistry of the present 

 year, for his valuable researches in this department of science. 



