Note 5 — Chapter VII · MOLECULES AND ATOMS. THE LAWS OF GAY-LUSSAC AND AVOGADRO-GERHARDT

This second law of volumes may be considered as a consequence of the first law. The first law requires simple ratios between the volumes of the combining substances A and B. A substance AB is produced by their combination. It may, according to the law of multiple proportion, combine, not only with substances C, D, &c., but also with A and with B. In this new combination the volume of AB, combining with the volume of A, should be in simple multiple proportion with the volume of A; hence the volume of the compound AB is in simple proportion to the volume of its component parts. Therefore only one law of volumes need be accepted. We shall afterwards see that there is a third law of volumes embracing also the two first laws.