A discussion covers some peculiarities of experimental studies of equilibria and phase processes in reacting systems with liquid splitting; some features of liquid-liquid (LL) systems with equilibrium and non-equilibrium chemical reaction in solution; experimental data on liquid phase splitting in multicomponent reactive systems; new experimental data on LL reactive systems; data sets for LL equilibrium (LLE) and CE at few temperatures; data on critical LL compositions for the quaternary acetic acid - n-propanol-water- n-propyl acetate and acetic acid- ethanol-water-ethyl acetate systems; critical states of LLE in the case of equilibrium chemical reactions; and possible transformations of the topological structure of diagrams of quaternary reactive systems. This is an abstract of a paper presented at the CHISA 2012 - 20th International Congress of Chemical and Process Engineering and PRES 2012 - 15th Conference PRES (Prague, Czech Republic 8/25-29/2012).