<P> John Dalton first expressed this observation in 1804 . A few years previously , the French chemist Joseph Proust had proposed the law of definite proportions , which expressed that the elements combined to form compounds in certain well - defined proportions , rather than mixing in just any proportion ; and Antoine Lavoisier proved the law of conservation of mass , which helped out Dalton . Careful study of the actual numerical values of these proportions led Dalton to propose his law of multiple proportions . This was an important step toward the atomic theory that he would propose later that year , and it laid the basis for chemical formulas for compounds . </P>
<P> John Dalton first expressed this observation in 1804 . A few years previously , the French chemist Joseph Proust had proposed the law of definite proportions , which expressed that the elements combined to form compounds in certain well - defined proportions , rather than mixing in just any proportion ; and Antoine Lavoisier proved the law of conservation of mass , which helped out Dalton . Careful study of the actual numerical values of these proportions led Dalton to propose his law of multiple proportions . This was an important step toward the atomic theory that he would propose later that year , and it laid the basis for chemical formulas for compounds . </P>
who said different elements combine together to form compounds
who said different elements combine together to form compounds
French chemist Joseph Proust
French chemist Joseph Proust