The commercial purity para-dichlorobenzene (p-DCB) and succinonitrile (SCN) were purified using a columnar distillation system. Thin-walled specimen cells (60-80 mu m thick) were fabricated and filled with the purified materials under the vacuum. A thin liquid layer was melted and the specimen was annealed in a constant temperature gradient for an enough time to observe the equilibrated grain boundary groove shapes. The thermal conductivities of solid and liquid phases for purified p-DCB and p-DCB-2.7 mole% SCN alloy were determined with the radial heat flow and Bridgman-type growth apparatuses. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficient and solid-liquid interfacial ene rgy of solid p-D(CB in equilibrium with p-DCB-SCN monotectic liquid have been determined to be (6.1 +/- 0.6) x 10(-8) K m and (29.2 +/- 4.4) x 10(-3) J m(-2). The grain boundary energy of p-DCB phase has been determined to be (54.6 +/- 9.3) x 10-3 J m(-2) from the observed grain boundary grooves. (C) 2007 Elsevier B.V. All rights reserved.