function s = equa(x)

% defines the Equation of State and the Boiling Relationship:
%
global m Vl;

V = 200;                % ft^3
MW = 18;
R = 10.73*1.8/14.7;     % atm.ft^3/(lb.mol.K)

Vg = V - Vl;

s(1) = x(2)*Vg - m*R*x(1)/MW;
s(2) =log10(218/x(2))-(647.27-x(1))/499*((3.346+4.14*10^(-2)*...
   (647.27-x(1)))/(1+1.38*10^(-2)*(647.27-x(1))));
