70 HISTORY OF CHEMISTRY. [LECTURE V. 



separate at the negative pole of the battery, while oxygen, the 

 acids, etc., separate at the positive pole. Besides this, they 

 believed that they had discovered relations between the 

 quantities of the substances decomposed, their mutual affinities, 

 and the quantities of electricity derived from the battery. 



With respect to the cause of the decomposition, they only 

 express themselves in a very uncertain manner ; they believe 

 that this decomposition may be explained by the greater or less 

 attraction that the electricity exerts upon the different substances. 



I now turn to Humphry Davy's investigations, which, as he 

 says himself, were begun in i8oo. c He commenced them with, 

 apparently, a quite unimportant question. Even in the first 

 experiments on the decomposition of water 7 it was believed that 

 the formation of alkaline and of acid substances as products of 

 the electrolysis had been observed. Cruickshank 8 and Brug- 

 natelli 9 confirmed this observation, and a belief was entertained 

 in the conversion of water into alkalies and acids under the 

 influence of the electricity. Simon 10 had already opposed this 

 view, and Davy refuted it by decisive experiments. 11 



Davy causes the decomposition to take place in vessels 

 made of different materials glass, agate, gold, etc. and satis- 

 fies himself that the nature and quantity of the substances 

 liberated are thereby varied. This leads him to the assumption 

 of the decomposition of the vessel. But even when he carries 

 out the decomposition in gold vessels, he observes the forma- 

 tion of the volatile alkali (ammonia) and of nitric acid. These, 

 he now concludes, owe their formation to the air (nitrogen) 

 which was dissolved in the water. In order to satisfy himself 

 of the accuracy of this view, he causes the decomposition to 

 take place in closed vessels, pumping out the air which is in 

 contact with the surface of the water, and substituting for it an 

 atmosphere of hydrogen. In this way he succeeds in proving 

 that pure water is decomposed by the action of the electric 



6 Phil. Trans. 1807, 2. 7 Nicholson's Journal (quarto), 4 (1801), 183. 

 8 Ibid. 188-189. 9 Phil- Ma g- 9> 181. 10 Gilb. Ann. 8 (1801), 36. 

 11 Bakerian Lecture for 1806 (Phil. Trans. 1807, i). 



