Wetting Transitions near Bulk Triple Points

The effect of a bulk triple point between phases $\alpha$, $\beta$, and $\gamma$ on the wetting, by films of $\beta$ or $\gamma$, of an $\alpha |\omega$ interface (between a wall $\omega$ and bulk $\alpha$) is discussed phenomenologically. Various additional wetting and surface transitions are induced by the triple point and may be pinned by it, and a compound ($\beta \gamma$) film may appear. The results are relevant to recent adsorption experiments and simulations.