<P> The ferric chloride test is used to determine the presence of phenols in a given sample or compound (for instance natural phenols in a plant extract). Enols, hydroxamic acids, oximes, and sulfinic acids give positive results as well . The bromine test is useful to confirm the result, although modern spectroscopic techniques (e.g. NMR and IR spectroscopy) are far superior in determining the identity of the unknown . The quantity of total phenols may be spectroscopically determined by the Folin - Ciocalteau assay . </P> <P> The sample is dissolved in water, or a mixture of water and ethanol, and a few drops of dilute ferric chloride solution is added . The formation of a red, blue, green, or purple coloration indicates the presence of phenols . Where the sample is insoluble in water, it may be dissolved in dichloromethane with a small amount of pyridine . </P>

What is the purpose of the fecl3 test