Vigorous mechanical stirring must be employed during the precipitation of the crude aldehyde, as otherwise large lumps are formed which make washing difficult. A previous investigator has mentioned that the crude product must be dried before distilling. This, however, is unnecessary. If the aldehyde is dried before distilling, it is possible to use a 500-cc. distilling flask instead of a 1-l one. In purifying the aldehyde by dissolving in acid and reprecipitating, it is essential not to use stronger acid than that specified (1:6), as stronger acid causes a deepening of the color of the solution. If the concentrated acid, which is to be diluted and used in this procedure, does not have a sp. gr. of 1.19, it will be necessary to add the equivalent amount of weaker acid in order to dissolve the _p_-dimethylaminobenzaldehyde. In purifying the aldehyde, sodium carbonate may be used in place of sodium hydroxide for precipitation, but it causes much foaming. When the apparatus for distilling, etc., is all set up, a run such as described above requires about five to six hours for completion. 3. Other Methods of Preparation _p_-Dimethylaminobenzaldehyde has been made by the condensation of chloral with dimethylaniline, and subsequent hydrolysis;[1] by the hydrolysis of tetramethyldiaminobenzhydrol with acetic acid;[2] by the condensation of dimethylaniline, formaldehyde and _m_-sulfo-_p_-tolyl hydroxylamine followed by hydrolysis;[3] by the electrolytic reduction of a mixture of sodium nitrobenzene sulfonate, dimethylaniline and formaldehyde, and subsequent hydrolysis;[4] by the reduction of a mixture of dimethylaniline, formaldehyde and sodium nitrobenzene sulfonate with iron and hydrochloric acid, followed by hydrolysis;[5] by the condensation of alloxan with dimethylaniline followed by hydrolysis;[6] by the condensation of dimethylaniline, formaldehyde and sodium _p_-toluidine sulfonate in the presence of hydrochloric acid and potassium dichromate followed by hydrolysis.[7] The most satisfactory method, however, is the condensation of dimethylaniline, formaldehyde and nitroso dimethy]aniline, followed by hydrolysis,[8] a method which was first described by E. Noelting and later perfected in detail by L. Baumann. [1] Ber. 18, 1519 (1885); 19, 366 (1886); D. R. P. 61, 551; Frdl. 3, 109 (1892). [2] Ber. 27, 3317 (1894). [3] D. R. P. 103,578; Frdl. 5, 101 (1899). [4] D. R. P. 105,103; Frdl. 5, 107 (1899). [5] D. R. P. 105,105; Frdl. 5, 109 (1899). [6] D. R. P. 108,086; Frdl. 5, 117 (1899). [7] D. R. P. 118,567; Frdl. 6, 133 (1901). [8] Ber. 37, 858 (1904); J. Biol. Chem. 41, 146 (1920). VI ETHYL OXALATE (CO2H)2 + 2 C2H5OH--> (CO2C2H5)2 + 2H2O Prepared by H. T. CLARKE and ANNE W. DAVIS. Checked by ROGER ADAMS and W. B. BURNETT. 1. Procedure