346 PRACTICAL ORGANIC CHEMISTRY Then add 3 drops of acetophenone (or about 0-3 g. of powdered benzo-phenone dissolved in i ml. of acetic acid) and shake the mixture. A precipitate of the phenylhydrazone is produced on scratching. ( b ) 2^-Dinitrophenylhydrazones. To a few drops of acetone, add a few drops of dinitrophenylhydrazine reagent A (p. 263): an orange-coloured precipitate is produced in the cold. Dissolve 0-5 g. of aceto-phenone or benzophenone in i ml. of methanol before adding the reagent B: orange-coloured precipitates are again produced, although that from benzophenone appears slowly. Filter and recrystallise the acetone derivative from ethanol, and the acetophenone and benzophe-none derivatives from benzene. (M.ps., pp. 541-542.) (c) Semicarbazones. Using acetophenone, proceed as described on p. 340 for the preparation of benzaldehyde semicarbazone. Note that many semicarbazones separate when the cold reaction-mixture is set aside for some time. (M.ps., pp. 541-542.)
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