The phase diagrams of following binary soap systems (soap = K-myristinate = KC14) were examined by polarization microscopy : system KC14/glycerol(G), KC14/ethylene glycol(E) and KC14/butylene glycol(E). Comparing these three phase diagrams, we found alterations in types of phase diagrams that depends on the chemical structure of the solvent. The following polymorphism were observed : In the system KC14/G : C <-> G <-> H <-> I <-> L <-> S (C = crystalline phase, G = gel phase, H = hexagonal phase, I = isotropic phase, L = lamellar phase, S = isotropic solution). In the system KC14/E : C <-> G <-> L <-> S and in the system KC14/B the same phase sequence : C <-> G <-> L <-> S. The differences in number, position, extension and sequence of occurring lyotropic mesophases are a function of the composition in the binary system and temperatures. The influence, which the solution medium exerts on the formation of structures in the binary systems, is distinct and pronounced.