Abstract: In this paper the solid reaction of phthalonitrile and rare earth acetates was studied by DTA method. Contrary to the earlier data from other laboratories. the authors have found that the formation of rare earth phthalocyanines is independent of the heating rate.Two kinds of rare earth coordination compound, i. e. mono-and diphthalocyanine were found in the reaction products, and the ratio of these two compounds varies with the heating rate and the kinds of rare earth used. Higher heating rate such as 20?/min is in favor of the formation of lutetium diphthalocyanine.