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.

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.