The investigations of the isochoric heat capacity of the 0.7168 (molar fraction) H2O + 0.1058 n-C6H14 + 0.1774 n-C3H7OH ternary system were made at constant composition in the range of temperatures (T) 314-590 K and densities (rho) 191.3-450.0 kg/m(3) with the adiabatic calorimeter. The curves of the phase equilibrium liquid-liquid and vapour-liquid were defined from jumps of the isochoric heat capacity. The forms of the phase equilibrium curves allow determining some special points. In the interval of densities 191.3-406.5 kg/m3 both lines of phase equilibrium have the forms of parabolas. Therefore, the special points are points of a maximum, which give the possibility to evaluate the forms of the left-hand and right-hand boundary curves. The following special point is the point of intersection of curves phase equilibria liquid-liquid and vapour-liquid, where occurs the duplication of the isochoric heat capacity jump on a isochore and the point at rho = 406.5 kg/m(3) and T = 496.15 K, in which we observe the sharp change of solubility character of the components.