The variations of enthalpy of three alloys (hypoeutectic, eutectic and hypereutectic compositions) are measured by the method of adiabatic drop-calorimetry for Sn-Pb system upon melting and heating in the field of liquid state. The experimental data are compared with the computing results for the cases of formation of homogeneous solution, mixture of two liquid phases inherited from solid eutectic and emulsion that includes the transition shells at the phase interface. Comparison supported the conception about eutectic melts as the microinhomogeneous systems of emulsion type.