Micellization of the CTAB in the Absence and Presence of Isoniazid in Alcoholic Media: Conductometric, Surface Tension, Viscosity, and Volumetric Approach

This experimental study evaluated the properties of density, conductivity, surface tension, and viscosity at three temperatures, alongside varying concentrations of 0.01 to 0.0001M Cetyltrimethylammonium bromide (CTAB) in 5% ethanolic solution of 0.001 M isoniazid (INH). The assessment involved calculating the ionization constant ( α ), critical micellization concentration (CMC), mole fraction of CMC, and thermodynamic parameters such as enthalpy (Δ H m 0 ), entropy (Δ S m 0 ), and free energy (Δ G m 0 ). Results indicated that the presence of INH decreases CMC while increasing temperature raises it. The solubility of CTAB in the drug solution is exothermic, as shown by negative Δ H m 0 values. Stronger hydrophobic interactions upon addition of a drug are denoted by greater positive values of Δ S m 0 . Negative Δ G m 0 values suggest thermodynamically spontaneous micellization in absence and presence of INH. Additionally, apparent molar volume calculations from density, the minimum area occupied by surfactant molecules ( A min ), maximum surface excess concentration ( Γ max ), molar Gibbs energy at CMC (Δ G min ), and Gibbs energy of adsorption (Δ G ads ) were analyzed. Viscosity analysis led to computations of the Falkenhagen coefficient ( A ) and Jones‐Dole coefficient ( B ).