The results are shown in Fig. 1. It can be clearly seen from Fig. 1 that all the sodium acetate solutions had no sour taste although they all contained anionic acetic acid species (AC1 ). However, all the solutions of acetic acid had an evident sour taste, and the intensity of sour taste increased as the concentration of all acetic acid species became elevated. The reasons for the difference in sour taste between sodium acetate and acetic acid solutions can be speculated from the differences in composition between sodium acetate and acetic acid solutions