The phenomenon of spontaneous bubble nucleation in extremely superheated binary solutions has been studied experimentally. The experiments were carried out by the pulse heating of a wire probe. Spontaneous boiling-up temperatures T* for solutions composed of components of different chemical nature have been measured in a wide range of variables, such as pressure p (up to the critical one p(c)) and composition (x similar to 0 divided by 1). For the most common types of the critical curve {T-c(x), p(c)(x)}, we have revealed the relationship between a change in the coordinates of the critical point and that of the attainable superheat line T*(p; x= const). This result leads to the natural choice of the program of further research including elucidation of the impact of the double metastability factor on the spontaneous boiling-up of solutions with different degree of compatibility of components. (C) 2017 Elsevier B.V. All rights reserved.