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).