The Gibbs-Dalton Law of Partial Pressures
ABSTRACT Various formulations of Dalton's law are investigated thermodynamically. The Gibbs formulation is shown equivalent to the statement: The concentration of a gas is the same at equilibrium on either side of a membrane permeable to it alone. The ordinary form of Dalton's law has only a limited equivalence with the Gibbs form. The Lewis and Randall rule of fugacity is shown in many ways analogous to the Gibbs-Dalton law. Application to experimental data shows that the Gibbs-Dalton law, like the Lewis and Randall rule, though possible for gases which do not follow Boyle's law, is only an approximation. In the cases examined, the errors are opposite in sign to those of the Lewis and Randall rule. An outline is given for the application of the Gibbs-Dalton law to the study of equilibrium in gases, and the useful field of application is indicated.