448 MODERN CHEMISTRY. 



exist without the presence of oxygen, and that the alkalies 

 and earths, with one exception, are compounds of this very 

 element with metallic bases. When, further, the discovery of 

 the new elements of chlorine, iodine, bromine, and fluorine, 

 multiplied the classes and distinctions of salts, the whole 

 theory became involved in a net-work of new names and 

 divisions, which it was an arduous task to unravel. Without 

 speaking of the oxygen, hydracid, sulphur, haloid, and poly- 

 basic salts (names which, as well as the word salts itself, may 

 best be viewed as provisional phrases only), we must simply 

 record our belief that Chemistry is here still far short of the 

 point it is destined to reach. The true road, however (first 

 indicated by Davy in his enquiry into the nature of chlorine), 

 seems now fairly laid open by the researches of Graham, 

 Liebig, Hofmann, Dumas, and other great chemists of our 

 own day. Water, in itself, and in the two elements composing 

 it, forms the foundation of the new doctrine. This wonderful 

 fluid, so widely diffused in nature, comes into direct operation 

 in almost every act of chemical change. It was already 

 known that its presence is essential to the crystallisation of 

 many bodies, and to the developement of certain acids. It 

 was further known that water is always separated in fixed 

 quantity, when an acid combines with alkalies or other bases 

 to form a salt. But these observations long remained barren 

 of result. It is only of late that chemistry, in recognising 

 hydrogen as essential to the constitution of a free acid, has 

 shown why water is necessary as furnishing this element. 

 In proving, further, that in the combination of acids with 

 alkalies or metallic oxides, the hydrogen is displaced by an 

 equivalent of the metallic base, and combines with the oxygen 

 set free from the latter, it shows the origin of the water 

 separated in the formation of neutral salts. 



What we thus briefly state, is the foundation of the 

 modern view of the constitution of acids and salts a 



