The systems HBBP — cyclohexane, HBBP — heptane, HBBP — acetone and HBBP — ethanol, HBBP —n-butyl-4-phenyl-n-hexyloxy-4′-benzoate have been studied by DTA. All the systems form a eutectic and comprise a limit range of nematic solution (after the metatectic reaction). Two new, solid an monotropic modifications have been discovered for HBBP at the transition temperatures of +4.5° and 19°. In the system HBBP — ethanol a region of demixture has been detected (according to the monotectic reaction), which is limited by a binodal curve with a maximum at approximately 54° and 23.5 mole % of HBBP.