A general method of predicting the water activity of ternary aqueous solutions from binary data

An isopiestic method has been developed to predict aw for ternary solutions from binary aw data. Another method, previously outlined by Robinson and Bower, has been extended to include non‐electrolytes. Both methods have been used to predict aw's for 51 representative systems. The results show that the isopiestic method is as good as, or better than Robinson and Bower's in predicting aw for ternary aqueous electrolyte/ electrolyte, electrolyte/non‐electrolyte and non‐electrolyte/non‐dectrolyte systems. Calculated aw values are in good agreement (<0.5%> error on the average) with experiment. The methods are applicable to relatively concentrated solutions up to 12 m.