In an experiment, 2.4 g of iron oxide on reduction with hydrogen, gave 1.68 g of iron. In another experiment, 2.7 g of iron oxide gave 1.89 g of iron on reduction. Which law is illustrated from the above data?

In first experiment,
Mass of iron oxide = 2.4 g
Mass of iron = 1.68 g
Mass of oxygen = 2.4 - 1.68 = 0.72 g
Ratio of masses of iron and oxygen = $\frac{1.68}{0.72}=7:3$
In second experiment,
Mass of iron oxide =  2.7 g
Mass of iron = 1.89 g
Mass of oxygen = 2.7 - 1.89 = 0.81 g
Ratio of masses of iron and ox[gen = $\frac{1.89}{0.81}=7:3$
The same ratio confirms that these experiments clarify Law of constant proportions.