Commercial- purity dichlorobenzene was purified using a columnar distillation system. The equilibrated grain boundary groove shapes for purified dichlorobenzene ( DCB) were directly observed by using a temperature gradient stage. From the observed grain boundary groove shapes, the Gibbs - Thomson coefficient and solid - liquid interfacial energy of purified DCB were determined to be ( 6.2 +/- 0.6) x 10(-8) K m and ( 29.3 +/- 4.4) x 10(-3) J m(-2) with the present numerical model and the Gibbs - Thomson equation, respectively. The grain boundary energy of the DCB phase was determined to be ( 54.1 +/- 9.2) x 10(-3) J m(-2) from the observed grain boundary grooves. The thermal conductivity ratio of the liquid phase to the solid phase was measured to be 0.94.