Abstract: As a result of the analysis, it is shown that when a drop spreads in the solid/liquid/vapor system, the same horizontal and vertical adhesion forces simultaneously act on the side of the solid surface particles. The heat of wetting is equivalent to the work of vertical adhesion forces.

Abstract: The equation of the critical surface tension was obtained on the basis of a new equation Young-Verkholomov contact angle. It is established that in the case of wetting of non-polar solids by non-polar liquids (the case of Zisman), the critical surface tension is equal to the corresponding value of the surface energy of the solid.

Abstract: On the basis of the mechanical model for solid body/liquid/vapour system the new equation of adhesion work at wetting solid surface by liquid phase is obtained. It was shown that the known Young-Dupre equation according to form is a particular case of the new Young-Verkholomov equation of contact angle.

Abstract: It is shown that according to the main physical characteristics the system solid/liquid/vapour can not be considered as a thermodynamic system. It is a kind of mechanical system.