Proust worked with the two samples of cupric carbonate one of which was of natural origin and the other was synthetic one. He found that the composition of elements present in it was same for both the samples as shown belowWhich law is in favour of the above data?

Law of definite proportions was given by, u French chemist, Joseph proust. He stated that a given compound always contains exactly the same proportion of elements by weight. Thus, irrespective of the source, a given compound always contains same elements in the same proportion.