THE CONSTITUTION OF MATTER. 
413 
which the idea of atoms has been gradually established in the minds of chemists. 
We have seen that Dalton’s belief in the existence of indivisible particles was 
founded solely upon a knowledge of the laws of definite chemical combination 
by weight. The results of analyses before Dalton’s time were represented in 
numbers which expressed the parts of each constituent in 100 of the compound. 
For example, iu red oxide of copper there are in 100 parts proportions as 
follows:— 
Copper . .88-8 
Oxygen .'.11-2 
1000 
In black oxide of copper :— 
Copper.79'87 
Oxygen .2013 
In carbonic oxide :— 
Carbon 
Oxygen 
100-00 
42-85 
57-14 
100-00 
27-27 
72-72 
100-00 
Dalton discovered reciprocal and multiple proportions by stripping from them 
the disguise in which this mode of representing composition enveloped them. 
For by taking some one of the elements in a compound as unity, and ascertain¬ 
ing by calculation the proportions which the others bear to it, it is easy to show 
that these proportions are simple multiples one of the other. 
In the instance of the two oxides of carbon, the composition of which has just 
been stated, if we calculate the ratio of the oxygen to the carbon in both of 
them, we find the proportion in the second double that in the first. Thus taking 
the carbon as unity :— 
Carbon. Oxygen. Carbon. Oxygen. 
42-85 : 57-14 :: 1 : 1 33 
And 27-27 : 72-72 :: 1 : 2-66 
Then plainly—• 
1-33 : 2-66 :: 1 : 2 
In other words, the proportion of oxygen in carbonic acid gas is double that 
contained in carbonic oxide. It must not be forgotten that there is another 
way of expressing the same fact, for by taking the oxygen as unity, instead of 
the carbon, we get the following proportions :— 
Oxygen. Carbon. 
57-14 : 42-85 :: 1 : -750 
72-72 : 27-27 :: 1 : -375 
Then 
•750 : -375 :: 2 : 1 
Or we may say carbonic acid contains half as much carbon as carbonic oxide. 
Similarly it will be found that the ratio of the oxygen in the oxides of nitrogen, 
of sulphur, and of many of the metals, will be as 1, 2, 3, etc., to 1 of the other 
constituent. 
In carbonic acid gas :— 
Carbon 
Oxygen 
