Abstract—: A study is performed of tetra-4-carboxyphthalocyanine hydroxyaluminum. The thermal effects of the dissolution of crystalline phthalocyanine in aqueous solutions with different concentrations of KOH are determined via direct calorimetry at a temperature of 298.15 K. The thermal effects of stepwise dissociation AlOHРс(4-COOH)4 are calculated using the HEAT computer program. The enthalpies of combustion of the studied compound are determined with an IKA C6000 isoperibol calorimeter (bomb calorimetry) and used to calculate the standard enthalpies of formation of AlOHРс(4-COOH)4 along with products of its dissociation in aqueous solutions. © 2025 Elsevier B.V., All rights reserved.