Law of Reciprocal Proportion Statement
The law of reciprocal proportions states that
If two different elements combine separately with a fixed mass of a third element, the ratio of the masses in which they do so are either the same as or a simple multiple of the ratio of the masses in which they combine with each other.
The law was proposed by Jeremias Richter which he used for neutralization of ratios of metals with acids. It was stated that:
When two substances A and B are chemically reactive with other two substances C and D, then the ratio of the quantities of C and D has the same amount of A as the ratio of the quantities of C and D has with B.
Law of Reciprocal Proportion Example
Consider 3 grams of C reacting with 1 g of H to form methane.
Also, 8 g of O reacting with 1 g of H to form water.
Here, the mass ratio of carbon and oxygen is 3:8.
Similarly, 12 g of C reacts with 32 g of O to form CO2.
The mass ratio of carbon and oxygen is 12:32 = 3:8
The mass ratio in which C and O combine with each other is the same as the mass ratio in which they separately combine with a fixed mass of H.