. A commentary on the scientific writings of J. Willard Gibbs. Gibbs, Joniah Willard, 1839-1908; Science; Thermodynamics. 296 SCHREINEMAKERS ART. H of the phase are first degree homogeneous functions of the mass variables. This proviso means that we assume we can neglect the surface effects which enter into the consideration of micro-heterogeneous systems. For given t and p, the f of a phase will depend, therefore, only on its composition. In the case of a binary system this composition is defined by the value of X (the composition parameter).. Fig. 1 In Fig. 1, in which WX = 1, the point a re
. A commentary on the scientific writings of J. Willard Gibbs. Gibbs, Joniah Willard, 1839-1908; Science; Thermodynamics. 296 SCHREINEMAKERS ART. H of the phase are first degree homogeneous functions of the mass variables. This proviso means that we assume we can neglect the surface effects which enter into the consideration of micro-heterogeneous systems. For given t and p, the f of a phase will depend, therefore, only on its composition. In the case of a binary system this composition is defined by the value of X (the composition parameter).. Fig. 1 In Fig. 1, in which WX = 1, the point a represents a phase containing Wa{= x) mols X and aX(= 1 — a;) mols W. If we now draw the ordinate aa' equal to the ^ of this phase, we shall call the point a' the f-point of the phase a. If we give all compositions, from pure W to pure X, to the phase a, then the point a runs along the line WX, whilst the point a' traverses a curve W'a'X', which, at constant t and p is called the f-curve (free energy curve). Clearly W is the f-point of the pure substance W and X' the f-point of the pure substance X. It can be shown that the f-curve touches the lines WW and XX' at the points W' and X' respectively (for proof see note at the end of this article). When all points of WX represent liquids, then W'a'X' is the f-curve of these hquids, whilst W' and X' are the ^-points of the pure liquids and a' that of liquid a. When the points of WX represent vapors (gases), then W'a'X' is the f-curve of these vapors, whilst W' and X' are the respective f-points of the pure. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Donnan, F. G. (Frederick George), 1870-1956; Haas, Arthur Erich, 1884-1941. New Haven, Yale University Press; London, H. Milford, Oxford University Press
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