The true identification of a drug may be accomplished in a number of ways, namely : determination of physical constants, chromatographic tests and finally the chemical tests. The physical constants essentially include the melting point, boiling point, refractive index, weight per millilitre, specific optical rotation, light absorption, viscosity, specific surface area, swelling power, infra-red absorption, and the like. The chromatographic tests include specific spot-tests by thin-layer chromatography (TLC) of pure drug or its presence in a multi-component system. However, the most specific and reliable are the chemical tests which may be categorized separately under tests for inorganic substances and organic substances. The former may be carried out by well defined general quantitative inorganic analysis and the latter by specific reactions of one or more of the functional moieties present in a drug molecule.