PROFESSOE THOMAS GEAHAm's SCIENTIFIC WORK. 187 



Society of Loudon an elaborate paper, entitled " Inquiries respecting- tbe 

 constitution of salts, of oxalates, nitrates, phosphates, sulphates, and 

 chlorides."* In it are recorded careful aualyses of very many salts, 

 more particularly in respect to their water of hydration ; with remarks 

 upon the greater or less tenacity with which the water is retained in 

 different instances. In this paper he put forward the notion that truly 

 basic salts are nevertheless neutral in constitution ; and that the excess 

 of metallic base does not stand in the relation of a base to the anhy- 

 drous acid, but as a representative of the water of hydration of the 

 neutral salt. He illustrated this position by a comparison of the defi- 

 nite hydrate of nitric acid with other hydrated nitrates, thus: 



Hydrated uitric acid, sp. gr. 1.42 HO. N O r, . :? H O. 



Hydrated uitrato of zinc Zn 0.N0f,.3 HO. 



Hydrated nitrate of copper : Cu . N O 5 . 3 H 0. 



Basic nitrate of copper HO. NOs.^CuO. 



He contended that, in the last cupric salt, it is the water and not the 

 oxide of copper which acts as a base ; and, in supi)ort of this view, he 

 remarked that if the water of the salt Avere water of hydration simply, 

 it ought, in presence of so large an excess of metallic base, to be very 

 readily expelled by heat ; whereas it is actually inexpulsable by any 

 heat whatever, short of that effecting an entire decomposition of the 

 salt. Again, he pointed out that when the strongest nitric acid HO.NO5 

 is added, in no matter what excess, to oxide of copper, the basic salt is 

 alone produced, apparently b^^ a direct addition of the oxide of copper 

 to the nitrate of water. 



In 1841 Mr. Graham gave to the Chemical Society "An account of 

 experiments ou the heat disengaged in co!nbiuation." t These experi- 

 ments included numerous determinations of the heat evolved in the 

 hydration of salts, and more particularly of the sulphates, including 

 sulphate of water, or hydrated sulphuric acid. Starting from oil of 

 vitriol H O. S O 3, he found that each successive addition of a proportion 

 of water HO, evolved an additional, but successively smaller and smaller 

 increment of heat; and that, even after the addition of fifty propor- 

 tions of water to the acid, the further addition of w ater was yet followed 

 by a perceptible development of heat. 



The relation of ether to alcohol being regarded as that of an oxide to 

 its hydrate, and expressed by the formulae C4H5O, and C4H5O.HO, 

 the conversion of alcohol into ether became a matter of dehydration ; 

 and, accordingly, could not escape the examination of Mr. Graham, 

 who, in 1850, presented to the Chemical Society some "Observations ou 

 etheriticatiou."! The process of manufacture consisting in the distil- 

 lation of a mixture of alcohol with sulphuric acid, and being attended 

 by an intermediate produetion of sulphate of ether or sul[)hethylic acid, 

 the substitution of ether for the basic water of suli)huric acid at one 



' * Pliilosophical Transactions, 1837, p. 47. 



t Chemical Society Memoirs, i, p. lOG. 

 t Chemical Society Journal, iii, p. 24. 



