In 1661 Robert Boyle summarized the properties of acids as follows.
Acids have a sour taste.
Acids are corrosive. Acids change the color of certain vegetable dyes, such as litmus, from blue to red. Acids lose their acidity when they are combined with alkalies. Vinegar tastes sour because it is a dilute solution of acetic acid in water. Lemon juice tastes sour because it contains citric acid.