Crystallization of 2RbBr . MnBr2 . 2H(2)O, the only double salt obtained un
der standard conditions from saturated aqueous rubidium-manganese bromide s
olutions, was theoretically predicted using the "hard" and "soft" Lewis aci
ds and bases concept and Pauling's rules. The RbBr-MnBr2-H2O system was the
rmodynamically simulated by the Pitzer model assuming a solubility diagram
of three branches only: RbBr, 2RbBr . MnBr2 . 2H(2)O and MnBr2 . 4H(2)O. Th
e theoretical result was experimentally proved at 25 degrees C by the physi
cochemical analysis method and formation of the new double salt 2RbBr . MnB
r2 . 2H(2)O was established. It was found to crystallize in a triclinic cry
stal system, space group -Pl, a = 5.890(1) Angstrom, b = 6.885(1) Angstrom,
c = 7.367(2) Angstrom, alpha = 66.01(1)degrees, beta = 87.78(2)degrees,gam
ma = 84.93(2)degrees, V = 271.8(1) Angstrom(3), Z = 1, D-x = 3.552 g-cm(-3)
. The binary and ternary ion interaction parameters were calculated and the
solubility isotherm was plotted. The standard molar Gibbs energy of the sy
nthesis reaction, Delta(r)G(m)degrees of the double salt 2RbBr . MnBr2 . 2H
(2)O from the corresponding simple salts RbBr and MnBr2 . 4H(2)O, as well a
s the standard molar Gibbs energy of formation, Delta(f)G(m)degrees, and st
andard molar enthalpy of formation Delta(f)H(m)degrees of the simple and do
uble salts were calculated.