FeCI3 test is used in diagnosis of ?

Ans. is 'd' i.e., Phenol Ferric chloride test is used to determine the presence or absence of phenols in a given sample. 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. The ferric chloride test can be used to detect metabolites in urine in case of inborn error of metabolism.