An equation for the activity coefficients and equilibrium relative humidities of water in confectionery syrups

Summary An apparatus is described for determining the equilibrium relative humidity (e.r.h.) of confectionery syrups and the results obtained are compared with those of other workers. The identity of e.r.h. with the thermodynamic activity is pointed out and an equation for the activity coefficient as a function of concentration is derived. The agreement between e.r.h. values calculated by means of this equation and experimental results is demonstrated and some of the advantages of the use of equations of this type are discussed, including the ability to draw significant conclusions about the nature of the solvent‐solute interaction.