Finding out pressure in a container if you know temp' and state-of-matter ratios

[Femme_physics]

Let's say you have a container with water in it. Let's say that you know that the temperature inside the container is 150 Celsius. Let's say that you have the ability to see inside the container and see the ratio of gas to liquid.

So, if you know the ratio and know the temperature, can you find out the pressure then by just looking at a phase diagram?

 

[Drakkith]

I would assume so if you had all the required values other than the pressure.

 

[Femme_physics]

Ah...chemistry. It just makes sense. Thanks :)