Phenol and water forni a partially consolute mixture. If the temperature be sufficiently lowered, solid phenol separates and we have a two-component system with two liquid phases, a solid phase and a vapor phase, and complete equilibrium at a definite temperature. The addition of hydrochloric acid, which is very soluble in water, but slightly soluble in phenol changes the relative miscibility of the two original components and the temperatures at which solid phenol can exist in the altered

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... m is raised. We will now have a ternary system with a solid phase, two liquid phases, and a vapor phase, consequently 'one degree of freedom, and since neither the water nor hydrochloric acid can separate in the solid phase, the system may not become non-variaii t so long as the phase liquid phenol persists. But the case under consideration can be made to assume special features. If we keep the mass of phenol YeZaativelTy small, water is so little soluble in it, that as the solid phenol separates, the concentration of the water hydrochloric acid is but slightly changed, and the freezing teiiiperature of the phenol remains very constant in a similar manner to the case which Nernst has already described.I Qualitatively, the case under consideration has been specifically discussed by Bancroft' in a study of ternary systems with two liquid phases, and he found that solid phenol was in equilibrium with liquid phenol and water at + 0.8', whereas the temperature rose to about 2 5 O when the laboratory acid, presumably Zeit. phys. Chem. 6, 30 (1890). * Jour. Phys. Chem. I , 420 (1897).