1. The problem statement, all variables and given/known data I am to estimate the critical temperature and critical pressure (where vapor and liquid merge) of a fluid. I am given that rho (the density), L (latent heat of vaporization), t_b (boiling temperature at 1atm) and P = 1atm (pressure) to be known. 2. Relevant equations dG = -S dt + V dp dp_s(T)/dT ~= L*rho/T 3. The attempt at a solution I'm pretty sure I'm supposed to use Gibbs free energy because it has the correct independent variables. and The boiling point at 1atm give me a point on the coexistence curve but I don't know how to proceed from here. the second equation I found for the coexistence curve, which might be helpful but I still don't have any idea of the next step.