1813.] Definite Proportions in Chemical Combinations. 35 



constituents of the different compounds formed by the union of 

 the different doses of oxygen with the base will be as follows: 



1st compound, a + b 

 2d compound, a + 2 b 

 3d compound, a + -3 b 

 4th compound, a + 4 b 



Suppose 10 parts of oxygen enter into the first compound, then 

 20 parts enter into the second compound, 30 parts into the third 

 compound, and 40 parts into the fourth compound. Hence, 

 whatever number of atoms of oxygen enter into the first com- 

 pound, twice that number enters into the second, thrice into the 

 third, and four times that number into the fourth. 



Hence it is clear that there is a determinate number of atoms 

 of oxygen which always enter into these combinations. If we 

 represent this number by x, then a + x is the first compound, 

 a + 2 x the second, a + 3 x the third, and a + 4x the fourth. 

 Now it would be singular if 2, 3, 4, &c. atoms of oxygen were 

 to be always inseparably linked together, so as never to be able 

 to enter into combinations separate. It is much more simple to 

 conceive that x represents only one atom. Even though the 

 opinion should not be mathematically true, still it would be 

 proper to adopt it : for as far as our calculations are concerned, a 

 number of atoms of oxygen constantly and invariably united 

 constitute a compound atom, about which we may reason as 

 accurately and justly as we could about the simple atoms them- 

 selves. Indeed, I think that x certainly represents one atom 

 only ; for oxygen gas being a permanently elastic fluid, must 

 consist of atoms that repel each other. Hence I conceive that 

 a compound atom of oxygen, or a number of atoms of it united 

 together, is impossible. And if x consisted of atoms not united 

 together, I can see no reason why the same number should unite 

 in eveij case (or a multiple of it) with other bodies. 



This reasoning may be applied to hydrogen as well as oxygen. 

 Hydrogen has the property of uniting in different proportions 

 with various bodies, a* with carbon, phosphorus, sulphur, &c. 

 in these different proportions we find the hydrogen a'lwavs 

 denoted by y, 2 ?/, fee. Hence we have every reason to con- 

 clurlc that y, which represents the proportion of hydrogen which 

 unites with the other constituent in these cases is an atom. 



The numbers x and y are easily discovered, by making an 

 accurate analysis of the different compounds into which various 

 proportions of oxygen and hydrogen enter, and when reduced to 

 then lowest terms they arc very nearly x = "-.t and // = I. Hence 

 ihce numbers represent the' ratios of the weight' of an atom of 

 oxu-.-n and an atom of hydrogen to each other!' Now it deserves 

 attention that these numbers represent the composition yf water. 



c 2 



