Identification Tests Benzoate

There are three identification tests for benzoates in the European Pharmacopoeia, test (a) in which benzoate is precipitated with a ferric salt to get the above-mentioned insoluble iron(III) salt, and test (b) and test (c), where the physical properties of benzoic acid are used for identification. 

The selectivity of the test is quite limited, even compared to the specificity seen in the identification test for chlorides. In the identification three criteria have to be fulfilled to qualify for a positive reaction. The unknown should give a white (curdled) precipitate formed upon addition of silver nitrate, which is insoluble in dilute nitric acid but redissolves in ammonia. In the limit test 2.4.4. Chlorides any substance capable of giving a white or weakly colored precipitate in dilute nitric acid will give a response like chloride, and this should be remembered in case of an xmexpected result. For the sake of example the following ions and substances are capable of giving a false positive reaction bromide, iodide, bromate, iodate, sulfite, chlorate, oxalate, and benzoate. In addition to this a variety of more complex organic substances are likely to precipitate, for example, alkaloids. 

Identification A 1 5 aqueous solution responds to the flame test for Potassium and gives positive tests for Benzoate, Appendix IIIA. 

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