

LECTURE V. 



DAVY'S ELECTRO-CHEMICAL THEORY DISCOVERY OF THE ALKALI 

 METALS DISCUSSION REGARDING THEIR CONSTITUTION DOES 

 HYDROCHLORIC ACID CONTAIN OXYGEN? HYDROGEN THEORY 

 OF ACIDS. 



IF we look back to the period when the alkalies were regarded 

 as simple and undecomposable substances, we can easily 

 understand the enthusiasm with which the chemical world 

 greeted the discovery of potassium and sodium. We are all 

 familiar with the remarkable properties of these elements with 

 their metallic appearance and low specific gravity, their change- 

 ability in the air, their easy inflammability upon water, etc. It 

 can be understood, therefore, that when substances possessing 

 such properties had once been seen, illusions of all kinds were 

 entertained by some people. The idea was arrived at that the 

 substances hitherto known were only compounds, and that the 

 aim of chemistry was now to discover the true elements, which, 

 it was supposed, would resemble potassium and sodium. It is 

 likewise comprehensible why the agency which had accomplished 

 such results should be admired and overestimated. Everything 

 was supposed to be possible by means of it, and the direction 

 which chemistry would necessarily follow that of electro- 

 chemical development was clear to every one. The galvanic 

 current, at that period an entirely new agent, had accomplished 

 this marvel, and it was itself a marvellous thing. By its aid it 

 had become possible to decompose compounds into their true 

 elements ; hence it is not surprising that this agency was re- 

 garded as identical with the one which gave rise to combinations, 

 i.e., with affinity. It was believed that an explanation was 

 thereby furnished for two things, both of which stood in need 

 of it that is to say, for electrical and for chemical phenomena, 



