The Law of Multiple Proportions states:
“When two elements combine to form two or more chemical compounds, the ratio between different weights of one of the elements which combine with a fixed weight of the other is always simple.” Examples:
- Compound of Carbon and Oxygen : C and O combine to form two compounds CO and C${{O}_{2}}$.
In CO, 12 parts by wt. of C combine with 16 parts by wt. of O.
In CO2,12 parts by wt. of C combine with 32 parts by wt. of O.
If the weight of C is fixed at 12 parts of wt. then the ratio in the weights of oxgyen which combine with the fixed wt. of C (= 12) is 16 : 32 or 1:2.
Thus the weights of oxygen bear a simple ratio of 1 : 2 to each other. 2 - Compounds of Sulphur (S) and oxygen (O):
S forms two oxides with O, viz. S${{O}{2}}$ and S${{O}{3}}$
In S${{O}{2}}$,32 parts by wt. of S combine with 32 parts by wt. of O.
In S${{O}{3}}$, 32 parts by wt. of S combine with 48 parts by wt. of O.
If the wt. of S is fixed at 32 parts, then the ratio in the weights of oxygen which combine with the fixed wt.
of S is 32:48 or 2 : 3.
Thus the weights of oxygen bear a simple ratio of 2 : 3 to each other