348 PRACTICAL ORGANIC CHEMISTRY 3. Heating vnth soda-lime. See Section 3, p. 327. Note that this test is particularly useful for providing evidence of: (a) Benzoic Acid. Gives benzene, detected by odour and by burning with a very smoky flame. ( b ) Salicylic Acid. Gives phenol, detected by odour and by violet coloration with ferric chloride solution (p. 338). (c) Phthalic Acid. Also gives benzene, but requires longer heating than benzoic acid. (d) Cinnamic Acid. Gives styrene, C 6 H 6 CH:CH 2 (characteristic odour) and usually benzene. 4. Ester formation. Heat gently i ml. of ethanol with 0-5 g. of the acid or one of its salts and a few drops of cone. H 2 SO 4 for about i minute. Cool and pour into a few ml. of water in a test-tube and note the odour. The test is particularly useful for identifying: (a) Acetic Acid. Ester has strong odour of apples. ( b ) Salicylic Acid. Ester has strong odour of oil of wintergreen. The methyl ester formed by substituting methanol for ethanol in the
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