Acetate Cellulose Strip

Potassium nitrate is a chemical compound with the chemical formula KNO₃. It is an ionic salt of potassium ions K⁺ and nitrate ions NO₃⁻, and is therefore an alkali metal nitrate. It occurs in nature as a mineral, niter. It is a source of nitrogen, from which it derives its name.

Formula: KNO3

Phenolphthalein is a chemical compound with the formula C₂₀H₁₄O₄ and is often written as “HIn” or “phph” in shorthand notation. Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and red in basic solutions.
Formula: C20H14O4

Sodium benzoate is a substance which has the chemical formula C₆H₅COONa. It is a widely used food preservative, with an E number of E211. It is the sodium salt of benzoic acid and exists in this form when dissolved in water. It can be produced by reacting sodium hydroxide with benzoic acid.