A CENTURY OF CHEMISTRY. 127 



one another, the importance of electrical phenomena 

 has bulked largely. The discoveries of Galvani 

 (1789) and Volta (1792) on the generation of elec- 

 tricity by the use of two metals were not long in 

 being applied to chemistry. Thus in 1800 Nichol- 

 son and Carlisle observed that if an electrical cur- 

 rent be passed through water, the result is a decompo- 

 sition into hydrogen and oxygen, — the two gases, 

 namely, which Cavendish, sixteen years before, had 

 shown (synthetically) to be the constituents of 

 water. In 1803 Berzelius and Hisinger published 

 the results of similar experiments on many different 

 compounds, and showed that hydrogen, metals, alka- 

 lis, metals, etc., possess positive electrical energy, 

 while oxygen, acids, etc., separate at the positive 

 pole. 



Davy. — Meanwhile Humphry Davy had also 

 turned his attention to similar enquiries ; he con- 

 firmed the results of Hisinger and Berzelius, and 

 made the theoretical suggestion that hydrogen, alka- 

 lis, metals, etc., possess positive electrical energy, 

 while oxygen and the acids are correspondingly nega- 

 tive. As oppositely electrified bodies attract each 

 other, the former substances come off in electrolysis 

 at the negative pole (cathode), and the latter at the 

 positive (anode). From this he went on to the mo- 

 mentous generalisation that chemical affinity is due 

 to difference in electrical condition. 



Pursuing his decomposition experiments, Davy 

 turned his attention to the alkalis (potash and soda), 

 and found that small metallic globules, burning with 

 brilliancy in air, were formed at the negative pole, 

 while oxygen was evolved at the other. He rightly 

 concluded that the substances he had discovered were 

 the metals Potassium and Sodium, of which the 



