Natural pH Indicators- A Review

A pH indicator is something that can tell you whether a substance is an acid or a base. A visual acid-base indicator is just a weak acid with differently colored acid and conjugate base forms. We know the color changes that we see in the nature all around us .We also notice the color changes in iced tea when lemon juice is added. In the study of acid base chemistry we use litmus paper to indicate if a solution is acidic, basic or neutral based on the color changes. Flowers and leaf pigments often fit this description. Many flowers, fruits and vegetables contain chemical substances that change color in solutions of different pH. All pH indicators change color depending on whether they donate or accept proton (acids are proton donors and bases are proton acceptors). Therefore pH indicators are themselves acids or bases.