# How can vapor pressure be lowered?

Jul 16, 2018

Just to retire this question, we can restrict the discussion to $\text{the saturated vapour pressure...}$, i.e. we consider the vapour pressure exerted by WATER only...
Now ${P}_{\text{SVP}}$ is a function of TEMPERATURE. Of course, when water (when any liquid) boils it has a vapour pressure EQUAL to the ambient pressure, and bubbles of water vapour form directly in the liquid. And so at $100$ ""^@C, ${P}_{\text{SVP}} = 1 \cdot a t m$ OR $760 \cdot m m \cdot H g$.
At OTHER temperatures, the vapour pressure of the water changes. Ice certainly exerts a vapour pressure. And tables of saturated vapour pressure are usually reported in $m m \cdot H g$. At $298 \cdot K$, liquid water exerts a vapour pressure of $24 \cdot m m \cdot H g$...and usually we have to account for the vapour pressures when gases (say) are collected under water. And so to reduce the vapour pressure we simply LOWER the temperature....