Law of multiple proportions

The law of multiple proportions was proposed by John Dalton in 1803, based on the observation that two elements can sometimes combine with each other to form MORE than one distinct compound. The law states that when two elements A and B are capable of forming more than one compound together, the different masses of element B that combine with one FIXED mass of element A always turn out to be in a ratio of small whole numbers. Two worked examples make this concrete. First, hydrogen and oxygen form two different compounds: water, where 2 g of hydrogen combines with 16 g of oxygen to give 18 g of water, and hydrogen peroxide, where the same 2 g of hydrogen instead combines with 32 g of oxygen to give 34 g of hydrogen peroxide — here the two oxygen masses combining with the fixed 2 g of hydrogen, 16 g and 32 g, are in the simple ratio 16:32, i.e. 1:2. Second, nitrogen and oxygen similarly form two compounds: nitric oxide, where 14 g of nitrogen combines with 16 g of oxygen to give 30 g of nitric oxide, and nitrogen dioxide, where the same 14 g of nitrogen instead combines with 32 g of oxygen to give 46 g of nitrogen dioxide — again the two oxygen masses, 16 g and 32 g, combining with the …