Ten or 20 g. of unchanged nitrotoluene can be recovered from the reaction mixture by steam distillation, but the value of the by-product would not pay for the time spent in recovery. The washing of the crude reaction product with dilute sulfuric acid is advisable, if good material is to be obtained. If an efficient centrifuge is available for use at this stage of the operation, this separate washing may prove to be less essential. When a sparingly soluble organic acid is precipitated from fairly concentrated solution, the precipitate is liable to carry down with it some of the salt of the organic acid. Addition of the salt solution to the mineral acid, with stirring, avoids this difficulty. 3. Other Methods of Preparation The nitration of benzoic acid produces only very small yields of the _p_-nitro product.[1] The only practical method for the preparation consists in the oxidation of _p_-nitrotoluene, although for this purpose various oxidizing agents are used. In addition to nitrotoluene, _p_-nitrobenzyl alcohol, _p_-nitrocinnamic acid and similar compounds may be oxidized, but their cost is prohibitive in comparison with that of the cheaper nitro hydrocarbon. _p_-Nitrotoluene may be oxidized by means of strong nitric acid,[2] chromic acid mixture,[3] or permanganates.[4] Electrolytic oxidation[5] has also been proposed. The procedure given above involves the use of chromic acid mixture, but, owing to a change in the concentration of sulfuric acid, the time of reaction is greatly shortened and the preparation is thus considerably improved. [1] Ber. 8, 528, 536 (1875) [2] Ann. 127, 137 (1863); 128, 257 (1863) [3] Ann. 139, 335 (1866). [4] J. Am. Chem. Soc. 41, 1575 (1919). [5] R. P. 117, 129; Frdl. 6, 112. XIV _ p_-NITROBENZYL CYANIDE C6H5CH2CN + HNO3--> (_p_)NO2C6H4CH2CN + H2O Prepared by G. R. ROBERTSON. Checked by ROGER ADAMS and H. O. CALVERY. 1. Procedure