Viscosity of liquid binary Pb–Zn alloys in the miscibility gap region

•Critical parameters of viscosity in the critical point region are evaluated.•Viscosity of monotectic alloys takes a finite value at the critical point.•Equation for relationship between the regular and fluctuation viscosity is proposed.•Universality principle spreads out to immiscible melts and dielectric solutions.

The shear viscosity studies were performed for the liquid Pb–Zn monotectic system over a wide temperature range using an oscillating-cup viscometer, with special attention to the critical point (CP) region. The critical parameters describing the peculiarities of the viscosity behavior in the vicinity of CP are evaluated. The data analysis is based on the dynamic theory of phase transitions and the viscosity equation, which takes into account a spatial dispersion of the systems near their critical temperatures. The results are compared with available data for immiscible dielectric solutions.