of too rapid crystallization. Under these conditions it is advisable
to crystallize again, using a somewhat larger amount of toluene.

It is advisable to titrate the crude anthranilic acid with standard
alkali and phenolphthalein before starting the experiment.
In checking these directions, an 80 per cent anthranilic acid
was used; it gave a correspondingly lower yield of methyl red
(650-700 g.). The yield of methyl red is about 65 to 70 per cent
based on the dimethylaniline actually used up, but only 58-63 per
cent based on the anthranilic acid actually present in the technical
anthranilic acid employed.


3. Other Methods of Preparation

Methyl red was first prepared[1] by diazotization of anthranilic
acid in alcoholic solution, the product being allowed to react with
dimethylaniline in the same solvent. It has been stated[2] that this
process does not work satisfactorily and yields a different product,
of brownish-red color.

The preparation of methyl red in aqueous solution has been
described by two workers, one of whom[3] gives but few details
and claims a nearly quantitative yield; the other[4] gives fuller
details and states the yield to be 43.1 per cent of the theory.
The recrystallization of methyl red from toluene is stated[5]
to yield a product melting at 183'0.

[1] Ber. 41, 3905 (1908).