By adding a large quantity of Cl[superscript -] to an aqueous solution of CoCl[subscript 2][multiplied by]6H[subscript 2]O, a mixture containing a red octahedral cobalt complex and a blue tetrahedral complex is produced. When the solution temperature is modified, the equilibrium constant, K[subscript eq], of the complexation reaction is shifted and the proportion of the two colored forms altered correspondingly. Absorbance spectrophotometry is utilized to determine the concentration of each cobalt species, allowing K[subscript eq] and the change in Gibbs energy, deltaG[degrees], values to be found at each temperature tested. By plotting deltaG[degrees] versus temperature, the changes in entropy and enthalpy for the reaction can be determined. (Contains 2 tables and 2 figures.)