Aspirin has been widely used as a pain killer for over 100 years. It has also been shown useful in lowering the risk of heart attacks and strokes. The active ingredient of a commercial available aspirin tablet is acetylsalicylic acid. Each tablet typically contains 100 mg or 300 mg of the compound.

The amount of acetylsalicylic acid present in an aspirin tablet can be accurately determined from a direct titration with a strong base such as sodium hydroxide. This is compared to the amount of acetylsalicylic acid determined by measuring the solution pH of an aspirin tablet.

The purity of an aspirin tablet is established using the technique of Thin Layer Chromatography.