The mass spectrum over {xNaBr + (1 - x)KBr}(s) measured at the temperature 800 K exhibits the ions Na+, K+, NaBr+, KBr+, Na2Br+, NaKBr+, and K2Br+. The excess molar Gibbs free energy of the solid solution has been obtained : G(m)(E)(800 K)/(J . mol(-1)) = x(1 - x)(10320 +/- 350). The temperature dependence of the standard equilibrium constant of the reaction of formation of NaKBr2(g) : Na2Br2(g)+ K2Br2(g) = 2NaKBr(2)(g), has been determined.