Activity of water in aqueous systems; a frequently neglected property.

In this critical review, the significance of the term 'activity' is examined in the context of the properties of aqueous solutions. The dependence of the activity of water(l) at ambient pressure and 298.15 K on solute molality is examined for aqueous solutions containing neutral solutes, mixtures of neutral solutes and salts.

The nature of the micellar stern region as studied by reaction kinetics. 2.

The nature of rate-retarding effects of cationic micelles on the water-catalyzed hydrolyses of a series of para-substituted 1-benzoyl-1,2,4-triazoles (1a-f) and 1-benzoyl-3-phenyl-1,2,4-triazole (2) has been studied using kinetic methods. A comparison is drawn between medium effects in the micellar Stern region and in model solutions for the micellar Stern region. Simple model solutions involving concentrated aqueous solutions of a small ionic molecule resembling the surfactant headgroup, as reported before,(1) were improved.

Three important calorimetric applications of a classic thermodynamic equation.

The thermodynamic background to three calorimetric techniques is discussed; (i) titration microcalorimetry, (ii) adiabatic calorimetry, and (iii) heat conduction calorimetry. Relevant equations for each technique are derived from a common equation for the enthalpy H of a closed system. General patterns which emerge in the measured parameters are presented for adiabatic and heat conduction calorimeters linked to applications of these techniques.

Kinetics of hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution as a function of temperature near the temperature of maximum density, and the isochoric controversy.

At temperatures above and below the temperature of maximum density, TMD, for water at ambient pressure, pairs of temperatures exist at which the molar volumes of water are equal. First-order rate constants for the pH-independent hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution at pairs of such isochoric temperatures show no unique features. Taken together with previously published kinetic data for the hydrolysis of a range of simple organic solutes in both water and D2O near their respective TMDs, we conclude that special significance in the context of rates of chemical reactions in aqueous solutions should not be attached to the isochoric condition.

Understanding organic reactions in water: from hydrophobic encounters to surfactant aggregates.

A crucial factor in realising a green chemical process in solution involves the choice of a safe, non-toxic and cheap solvent. Water is the obvious choice. Despite solubility problems, considerable interest has developed recently in organic chemistry in water.