Precise density and viscosity measurements on ternary solutions (polyhydroxy solute + NH 4 Br + H 2 O) have been carried out over the temperature range (288.15 to 318.15) K at atmospheric pressure. Partial molar volumes, V 2°a t infinite dilution and the Jones-Dole B-coefficients obtained from above data were utilized to estimate the transfer parameters (Δ t V 2°a nd Δ t B) for polyhydroxy solutes. The interaction coefficients were obtained from the transfer values using the McMillan−Mayer theory of solutions. Isobaric expansion coefficients and second-order derivatives {(∂V 2°/ ∂T) P , (∂ 2 V 2°/ ∂T 2 ) P }, and dB/dT coefficients were also determined to study the effect of temperature. These parameters were used to understand the kosmo-/chaotropic nature of solutes and cosolute which is helpful in rationalizing the mixing effects due to interactions between them in these solutions, concomitantly keeping the stereochemical differences of the polyhydroxy solutes in view.

Surfactant micelles mimic the microenvironment present in biological systems and can act as a medium for antioxidant studies. Moreover, the thermodynamic profile of micellization and spectroscopic studies provides very good information about interactions in these systems. Thus, the mixed micellar behavior of sodium dodecylsulfate (SDS) and cetyltrimethylammonium bromide (CTAB) at varying mole fractions of SDS was studied in (0.01, 0.02, and 0.03) mol kg−1 ʟ‐ascorbic acid(aq) solutions with the aid of various techniques viz., conductivity, density and sound velocity, and spectroscopy. From the CMC values of the mixed surfactants, the degree of ionization (β) and thermodynamic parameters (normalΔGm°, normalΔHm°, and normalΔSm°) were evaluated at 298.15, 308.15, and 318.15 K. The UV absorption spectra were recorded in (1–3) × 10−4 mol kg−1 ʟ‐ascorbic acid(aq) solutions at various mole fractions of SDS. The proton (1H) NMR spectra of mixed (SDS + CTAB) surfactants were studied in (0.01–0.03) mol kg−1 ʟ‐ascorbic acid solutions. Hydrodynamic diameters (Dh) of mixed micellar aggregates were obtained from the dynamic light scattering (DLS) studies. The present studies suggest the predominance of ionic‐hydrophilic interactions between the ionic head groups {O‐SO3− or N+ (CH3)3} of surfactants and the polar (–OH, –C=O and –O–) sites of ʟ‐ascorbic acid.

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