It leads on to another question - how can we calculate the partial "liquid" pressure exerted by a certain species in liquid phase, or partial "solid" pressure exerted by a certain species in solid phase (given that in the above case we were dealing with "gaseous" partial pressure), which would represent the (P,T) points for parts of the phase diagram in the solid or liquid phase regions? What are these 2 new kinds of pressure to be written as a function of, in other words (assuming we cannot set the pressure ourselves externally) - volume and temperature (what is our substitute for the ideal gas equation)? Because so far I've only worked with gaseous pressures until now.

I read that thrice. Does not make any sense to me. Sorry.

On a phase diagram which is a (P,T) and phase graph, pressure extends to liquid and solid phase species of the component for which the diagram is written. Concepts of pressure apply not only to gases but also to liquids and solids.

"Gaseous" pressure can be approximated, for instance, as P≈nRT/V. In general P=f(T,V,n) is true for any gas (a power series is the highest level method for approaching exactness), where T is temperature, V is volume and n is number of moles of that gas, and P is the partial pressure exerted by that gas. In this case, P would be the total pressure in the single-component system.

What can we say, similarly, about pressures for liquids and solids?

I remember being told by Corribus that the pressure exerted by liquids and solids does not contribute at all to that experienced by gases (partial pressure for a single species is strictly a function of T, V and n;

*maybe* of T, V taken up by the gaseous phase as a whole and n for each gaseous phase species), though gaseous pressure can affect the pressure exerted on a liquid or solid phase. What are the liquid and solid phase species' partial pressures a function of, then? I ask because I have very little knowledge of how pressure is dealt with when it comes to non-gases.