If the flask is not protected with an asbestos board or the equivalent, decomposition occurs where the substance is super-heated on the side walls of the flask. If crystals of the cyanide are allowed to remain on the upper walls of the flask, they are not easily washed down and so are not hydrolyzed.
The solubility curve of p-nitrophenylacetic acid is very steep at temperatures near 100'0, so that the filtering of the boiling solution should be rapid.
If a good grade of cyanide be used, it is not necessary to add bone-black in order to obtain the acid in a pure state.
In making experiments with 500 g. of p-nitrobenzyl cyanide, it was found that the time for hydrolysis was about the same as when smaller amounts were used.
3. Other Methods of Preparation
p-Nitrophenylacetic acid has been formed by the nitration of phenylacetic acid;[1] by the hydrolysis of its ester[2] or its amid,[3] and by the hydrolysis of its nitrile with hydrochloric acid.[4]
[1] Ber. 42, 3596 (1909).
[2] Ber. 12, 1765 (1879).
[3] Ber. 14, 2342 (1881).
[4] Ber. 15, 834 (1882).