28 HISTORY OF CHEMISTRY. [LECTURE II. 



disquisitions, which contain the annihilation of the preceding 

 system, only appear towards the end of his short and brilliant 

 scientific career. At first there was no explanation forthcoming 

 for a series of phenomena which were in agreement with Kirwan's 

 phlogiston theory. I refer to the behaviour of the metals 

 towards acids ; to the hydrogen liberated ; and to the reduc- 

 tions carried out by Priestley by means of hydrogen. It is 

 only after the composition of water has been ascertained by 

 Cavendish, Watt, and Lavoisier, 38 that Laplace arrives at the 

 idea (as Lavoisier relates 39 ) that on dissolving metals by means 

 of acids, water is decomposed that the hydrogen is, therefore, 

 evolved from the water, while the oxygen of the latter unites 

 with the metal to form an oxide. The phenomena of reduction 

 now become clear also. The hydrogen unites with the oxygen 

 of the metallic oxide, forming water, and the metal remains 

 behind. Lavoisier tries to prove all these points by a series of 

 excellent experiments. His investigations upon the decom- 

 position of water, are, especially, of extreme interest. 40 He 

 passes water vapour over weighed iron turnings, heated to red- 

 ness, and collects the hydrogen in an eudiometer. In this case 

 also, he weighs everything the water, the gain of the iron, and 

 the hydrogen. In this way, he succeeds in finding out the 

 quantitative composition of water; and the latter, along with 

 the quantitative composition of carbonic anhydride, which he 

 determines somewhat later, 41 constitute the starting point for 

 his researches on organic analysis. 42 



I wish to say a few words at least with regard to these 

 researches ; since, even although the numbers obtained are not 

 very exact, the methods are so important that I cannot pass 

 them by unmentioned. 



Lavoisier places a weighed piece of charcoal in a dish, 

 under a bell-jar containing a measured volume of oxygen, and 



38 With respect to the part played by each in this most important dis- 

 covery, compare Kopp, Die EntdeckungderZusammensetzungdes Wassers. 

 Beitrage. 3, 235. 39 Lavoisier, Oeuvres. 2, 342. 40 Ibid. 2, 360. 



41 Ibid. 2, 403. 42 Ibid. 2, 586. 



