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Slide #16 of this presentation on amalgams says that "Langmuir's equation" provides a specific "theoretical maximum evaporation rate" for liquid Hg as a function of temperature and surface area.

The only common equation bearing Langmuir's name is his adsorption model. I can vaguely imagine that model being applied in reverse to characterize evaporation rates, but I can't see or find how in general, much less in the specific case asserted in the paper. Can someone provide a reference or example of how that (or any other model) provides a "theoretical maximum evaporation rate" of a particular liquid?

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That most likely refers to the Hertz-Knudsen equation, also known as Knudsen-Langmuir equation. It is the most simplified model of evaporation in which no discussion is given into the diffusivity and the chemical potential gradient (let alone other driving forces like gravity and pressure gradient): one just assumes the leaving mass flux is dictated by the system's thermal energy. This model then suggests a direct relation between evaporation rate and vapor pressure, temperature and molar mass.

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