The complexation reaction between the macrocyclic ligand, benzo- 15- croun-5 (B15C5) with Al3+ cation was studied in pure methanol (MeOH), propanol (PrOH), methylacetate (MeOAc), ethylacetate (EtOAc) and their binary mixed solventswith acetonitrile (AN) at different temperatures using electrical conductometry method [1]. The conductance data show that the stoichiometry of complex formed between B15C5 and Al3+ in all solvent systems is 1:1(ML).Th e value of formation constant of the complex was determined from computer fitting of conductance versus mole ration data using a GENPLOT computer programme. In most cases, a non-linear relationship was observed between the stability constant (log Kf ( of the complex and the composition of the binary mixed solvent solutions [2,3]. The values of the standard thermodynamic parameters ( ) for formation of) B15C5.Al) 3+ complex obtained from the temperature dependence of the formation constant of the complex using the v'ant Hoff plots andthe data show that the standard thermodynamic quantities change with the composition of the binary solvent solutions.

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