'Law of multiple proportions' was first studied by Daltion in 1803 which may be defined as follows
When two elements combine to form two or more chemical compounds, then the masses of one of the elements which combine with a fixed mass of the other, bear a simple ratio to one another.
e.g., hydrogen combines with oxygen to form two compounds, namely, water and hydrogen peroxide.
Here, the masses of oxygen (i.e., 16 g and 32 g) which will combine with a fixed mass of hydrogen (2g) bear a simple ratio, i.e., 16:32 or 1:2.
As we know that, when compounds are mixed in different proportionations, then they form different compounds. In the above examples, when hydrogen is mixed with different proportion of oxygen, then they form water or hydrogen peroxide.
It shows that there are constituents which combine in a definite proportion. These consituents may be atoms. Thus, the law of multiple proportions shows the existence of atoms which combine into molecules.
