The global phase diagram of a binary mixture described by the Redlich-Kwong
equation of state has been calculated for the molecule volume ratio b(11)
: b(22) = 13 : 7 and the linear mixing rule for the molecular volumes. Boun
dary states separating regions with different topology of azeotropic lines
("horn" region with double azeotropy and "dish" region with an azeotropic l
ine connecting two critical azeotropic points) are found and discussed in c
onnection with other already known non-azeotropic phenomena.