"What I want to do today is finish the second installment of phase diagrams. Last day, we looked at unary phase diagrams. That is to say, single component. That meant all we had to do was worry about pressure versus temperature because everything is of simple composition. And I have up here on the display a phase diagram of water which we looked at last day. And I have redrawn it here for convenience. And I just wanted to draw your attention to several things. We are looking at how the stability of the different phases of water varies with pressure and temperature..."