i 7 4 PRACTICAL ORGANIC CHEMISTRY REACTIONS OF PICRIC ACID, (i) The presence of the three nitro groups in picric acid considerably increases the acidic properties of the phenolic group and therefore picric acid, unlike most phenols, will evolve carbon dioxide from sodium carbonate solution. Show this by boiling picric acid with sodium carbonate solution, using the method described in Section 5, p. 330. The reaction is not readily shown by a cold saturated aqueous solution of picric acid, because the latter is so dilute that the sodium carbonate is largely converted into sodium bicarbonate without loss of carbon dioxide. (2) To a cold aqueous solution of picric acid, add about an equal volume of dilute potassium cyanide solution. An orange coloration develops and rapidly darkens to a deep red. USES OF PICRIC ACID. The following further reactions of picric acid are used for analytical purposes in the laboratory. (3)
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