n, 1990, p. 10). Parts of his ideas echo the earlier law of conservation of mass and of definite proportions.
The elements that make up chemical compounds are easily identified from the formula used for the compound. For example, the formula for sodium chloride is NaCl--one sodium atom for each chlorine atom (the one is dropped off by convention and is merely assumed to be present). Together, they form a molecule, a diatomic molecule to be precise, because the lack of subscript numbers next to the atom's designation denotes that only one atom of each element is involved. In the formula for carbon dioxide, C02, the subscript numeral tells the chemist that two oxygen atoms are needed for each carbon atom in order to create the compound. When two elements form a series of compounds, however, the masses of one element that combine with the fixed mass of the other element stand to one another in the ratio of small integers, thus making up the law of multiple proportions (Oxtoby, Nachtrieb and Freeman, 1990, p. 12).
With the law of combining volumes, Fre
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