448 On the Cause of Chemical Proportiwis. [Dec. 



This law, though in itself conformable to the corpuscular theory, 

 admits, on the one side, of combinations inconsistent with that 

 theory ; and, on the other hand, it excludes combinations per- 

 fectly conformable with that theory. I shall explain this by an 

 example. Let O be oxygen, A and B two combustible bodies. 

 The law which we are considering admits of a combination of 

 A + 3 O with 14- B O, because Ii. x 2 = 3: and we shall 

 see immediately that such combinations exist, though, according 

 to the. corpuscular theory, they appear absurd. On the other 

 hand, the law does not admit the combination of A + 3 O with 

 B + 2 O, though such a combination be conformable to the 

 theory of atoms. The black oxide of copper is composed, 

 according to our present knowledge, of 1 atom of metal and 2 

 atoms of oxygen, and sulphuric acid of 1 atom of sulphur and 

 3 atoms of oxygen. We know that there is a subsulphate of 

 copper in which the acid and the oxide contain each equal quan- 

 tities of oxygen. Of course, this subsulphate must contain for 

 every atom of sulphuric acid an atom and a half of oxide of 

 copper. It is true that we may object to this, that there is some 

 appearance that sulphuric acid is composed of 6 atoms of oxygen 

 to 1 of sulphur. But I shall have occasion to discuss this opinion 

 when I come to speak particularly of sulphur. Arsenic acid, 

 from new experiments of which 1 shall give an account in the 

 sequel, is composed of 1 atom of arsenic and 6 atoms of oxygen. 

 The yellow oxide of lead is composed of I atom of metal and 2 

 atoms of oxygen. The arseniate of lead is composed in such a 

 manner that the acid contains three times as much oxygen as the 

 oxide, that is to say, of an atom of acid and an atom of oxide. 

 The subarseniate of lead is composed in such a manner that the 

 acid contains twice as much oxygen as the oxide; that is to say,. 

 of an atom of acid and an atom and a half of oxide. 



If we suppose that the yellow oxide of lead contains but one 

 atom of oxygen, this subsalt ceases to be an objection to the 

 atomic theory ; but in that case we meet with an equally for- 

 midable objection in the composition of the red oxide of lead. 



I have endeavoured to prove that two different oxides of the 

 same radicle sometimes combine in such a manner that each 

 contains an equal quantity of oxygen, or that the one contains 

 two, three, &c. times as much as the other. Among these 

 combinations there are some which do not agree with the hypo- 

 thesis of atoms : for example, the red oxide of iron contains 3 

 volumes of oxygen, and the black oxide 2 volumes. Gay-Lussac 

 has lately found that the oxide of iron formed at a high tempera- 

 ture by the action of the vapour of water is composed of 100 

 iron + 3/8 oxygen. But this combination of the two oxides is 

 composed in such a manner that the red oxide in the compound 

 contains exactly twice as much oxygen as the black : that is to 



