How does changing the amount of one substance affect a mixtures identity and a compounds identity iscience?

According to the Law of Definite Proportions from Dalton's Atomic Theory, every compound has a fixed ratio of the mass or moles of its individual elements. This is obeyed by balancing the reactions through stoichiometric coefficients. When you increase the concentration of one substance by adding its amount, then, the other elements would also increase in order to maintain that fixed ratio.