260 Mr. J. J. Thomson on the 



a= 40*1, so that whenever hydrogen and iodine are mixed 

 with some monovalent substance which combines with the 

 hydrogen, but not with the iodine, the number of molecules 

 of hydriodic acid is about 6*2 times the geometric mean of 

 the numbers of the free hydrogen and iodine molecules, and, 

 generally, equations (25) show that in all cases of combina- 

 tion of this kind the number of molecules of the compound 

 AB bears to the geometric mean of the numbers of free mole- 

 cules of A and B a ratio which is independent of the nature 

 of the substance C, and similarly the number of AC mole- 

 cules bears to the geometric mean of the numbers of the 

 uncombined A and C molecules a ratio which is independent 

 of the nature of B. 



§ 6. I have not been able to find any researches bearing 

 on the kind of chemical combination considered in the last 

 paragraph ; but as the somewhat analogous combination which 

 takes place when hydrogen, carbonic oxide, and oxygen are 

 mixed together and then exploded has been studied by several 

 chemists, we shall in this paragraph investigate theoretically 

 the result of such combination, although the case is not one 

 where we should expect to find a very close agreement between 

 the calculated and the observed results, as so much heat is 

 generated in the explosion that the temperature must vary 

 greatly during the time combination is taking place, and thus 

 complicate the question. We shall suppose that water is 

 produced by the combination of a molecule of hydrogen with 

 an atom of oxygen, and carbonic acid by the combination of 

 a molecule of carbonic oxide with an atom of oxygen ; we 

 shall also suppose that the hydrogen does not combine with 

 the carbonic oxide. 



Let m = the number of hydrogen molecules. 

 n = the number of oxygen atoms. 

 p = the number of oxygen molecules. 

 r = the number of carbonic oxide molecules. 

 s = the number of water molecules. 

 u = the number of carbonic acid molecules. 

 ti = the time two hydrogen atoms remain together in 



the hydrogen molecule. 

 t 2 = the time two oxygen molecules remain together 



in the oxygen molecule. 

 t d = the time an oxygen atom stays with a hydrogen 



molecule in the water molecule. 

 t 4 = the time an oxygen atom stays with a carbonic 



oxide molecule in the molecule of carbonic 



acid. 



