PURPOSE: To obtain the subject composition reduced in the discoloration due to solar light, fluorescent lamp light, etc., and useful as a raw material for heat-resistant pigments, a heat-sensitive coloring agent, etc., by reducing a specific photocoloration-causing substance contained in 4,5,6,7-tetrachloro-1,3- diiminoisoindolenine to ≤ a specific amount.

CONSTITUTION: This composition comprises 4,5,6,7-tetrachloro-1,3- diiminoindolenine (A) and ≤2wt.% of 1,2,3,4,5,8,9,10,11,12,14,14-dodecachloro-7- ketodibenzo[c, h]-6,11-diazepine (B) contained in the compound (A). The composition is obtained e.g. by adding 50-20000 pts.wt. of ammonia water and, if necessary, 1-1000 pts.wt. of an organic solvent as a slurry auxiliary agent to 100 pts.wt. of the crude compound A, slurrying the mixture, heating the slurry at 60-90°C, preferably for 30min to 1hr in the case of 90°C, for 4-6 hrs in the case of 80°C, or for 15-23hr in the case of 60°C, filtering the treated product, washing the obtained cake with water and an organic solvent, and subsequently drying the washed cake.