# Law of Reciprocal Proportions


The law of reciprocal proportions was proposed by Jeremias Ritcher in 1792. It states that, "If two different elements combine separately with the same weight of a third element, the ratio of the masses in which they do so are either the same or a simple multiple of the mass ratio in which they combine."

##### Example

Oxygen and sulfur react with copper to give copper oxide and copper sulfide, respectively. Sulfur and oxygen also react with each other to form SO2. Therefore,

in CuS:

Cu:S = 63.5:32

in CuO:

Cu:O = 63.5:16

S:O = 32:16

S:O = 2:1

Now in SO2:

S:O = 32:32

S:O = 1:1

Thus the ratio between the two ratios is the following:

$\dfrac{2}{1} : \dfrac{1}{1} - 2:1$

This is a simple multiple ratio.

Law of Reciprocal Proportions is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Binod Shrestha.