Solid-phase (s) decomposition reactions A(s) <----> B-s + nuC(g), (1) CaCO3 = CaO+CO2, or A(s) <----> SigmanuC(g), and reactions (2) C+CO2 = 2CO, (3) 2NH(3) = N-2 +3H(2), (4) CH3OH = CO+2H(2), were analyzed in terms of the equation Inalpha = a(o) - a(1)/T - a(2)InT and the relative reaction rate -dInalpha/d(1/T) = a(1) - a(2)T at T = const, 0.1 MPa. The equations were verified in terms of alpha(eq) vs. T profiles, where alpha is the degree of conversion (alpha(eq) at equilibrium). The term -a(2)InT was found to supplemenilhe temperature criterion (In alpha = -E/RT + C (E, C - const.)) and to expand its meaning at 0 < alpha < 1 and at higher T, but then a(1) has no longer its former physical meaning. Reactions (1)-(4) can be analyzed in terms of the temperature criterion at 0 < alpha < 0.2 and with the three-parameter equation over 0 < alpha < 1. High a(2) (e.g., 100) shows temperature to be a more intensive factor and this enables optimum reaction conditions to be chosen.