i8I4.] o« the Cause of Chemical Proportions-. 177 



black oxide ; and with 42 oxygen by heat, &c. forming llie red 

 oxide. Hence 50 iron combine with 14 oxygen and with 21, and 

 the combination of 50 iron with 7 oxygen to form the protoxide is 

 unknown. It was in conformity with this reasoning that I pub- 

 lished in the second part of my Chemistry, in 1810, t!ic atom of 

 iron to weigii 50. The details were not given, because I was not 

 then describing the oxides, 'Hie facts are not at all at variance 

 with the atomic theory ; but it appears a strange circumstance that 

 the first oxide cannot, by any means w^e are 3'et acquainted with, 

 be obtained, wliilst the second and third are readily. Tlie circum- 

 stance, however, is not without parallels. We well know that 

 sulphur takes 2 portions of oxygen to form sulphurous acid, and 3 

 to form sulphuric; but we scarcely recognise a com])ound of sulphur 

 with 1 portion of oxygen. Again, carbonic acid gas has been 

 known time immemorial ; but carbonic oxide gas has been known 

 only about twelve years ; yet it is pretty evident that the latter is, 

 theoretically, the more simple combination of the two. 



The second difficulty which Dr. Berzelius states is so obscurely 

 expressed that it requires an acute atomist to perceive the force of 

 it. This may, perhaps, be partly owing to the translation, and to 

 an error of the press, which last, however, is pretty readily cor- 

 rected. He has discovered a law (which, for thes^ke of argument, 

 I siiall take for granted to be true,) " that when two oxides com- 

 bine they always unite in such proportions that each contains either 

 an equal quantity of oxygen, or the one contains a quantity which 

 is a multiple by a whole number of the oxygen in theother.'"il)is law, 

 though in itself conformable to the corpuscular theory, admits, (he 

 says) on the one side, of combinations inconsistent with that theory ; 

 and, on the other side, it excludes combinations perfectly conform- 

 able with that theory. To illustrate these positions, he gives several 

 examples: 1 shall take the first two. Let O be oxygen, A and B 

 two combustible boilies ; then A + 3 O may combine with B + 

 1-J- O, because 1,^ x 2 = 3; and (he asserts) that such combina- 

 tions exist, though according to tiie corpuscular theoiy they appear 

 absurd. Now 1 think it mu->t be obvious that this second dilHculty 

 is the same as the first, and admits of the same explanation which 

 Berzelius has given ; namely, that the body, B, in such case has in 

 reality .'i atoms of oxygen for \ of metal, the quantity of which 

 oxygen we chuse to exj)ress by 1a. And tlie union in question is I 

 atom of ti\c third oxide of B with 2 atoms of the third oxide of A, 

 a combination perfectly consistent with the atomic theory, as well 

 as with tiie law and the exan)ple just exhibited to view. Tlie other 

 example is, that the law docs not admit A + .'! O to unite with B 

 -f- 2 O, though sucli combination be conformable to the theory of 

 atoms. In reply to this, 1 may observe, that it is not the pecidiar 

 biisiric-s of the atomic theory to explain why A + 30 do not unite 

 with li + 2 O, any more than to show why all the metallic oxides 

 <lo not mutuallv ccjmblnc with each other j for it may be said there 

 Vol. m. iVJIl. JVI 



