Abstract
The calorimetric procedure was attempted to study the solubilizing action of acid amides in aqueous solution. The interaction of nicotinamide and xanthine derivatives (caffeine, oxyethophylline, and theophylline) was studied by using the twin-type microcalorimeter. The positive heats of reaction were obtained between nicotinamide and xanthine derivatives. By using these values, the heat of complex formation (ΔHf) and complex formation constant (K) between them were calculated by the method described by Lamberts. These values obtained by the calorimetric procedure agreed with corresponding values by the solubility method. This procedure was very easy for obtaining ΔHf and K, and therefore it was considered to be one of the useful methods for studying the interaction between a solubilizing agent and a solubilizate.
