The product is extracted with boiling toluene in the following manner: 150 g. are placed in a fluted filter paper of 29 cm. diameter in a 25-cm. glass funnel which passes through the cork of a 2-l. flat-bottom conical flask containing 1250 cc. of toluene (Fig. 2). The flask is heated on an electric stove, and a 12-l. round-bottom flask is placed on the funnel to act as a condenser, cold water being run through the flask. The toluene is boiled until the condensed liquid runs through almost colorless (this requires from four to ten hours). The heating is then discontinued, and, as soon as the liquid ceases to boil, the flask is removed to a bath containing water at 90-100'0; the level of the water should be slightly above the level of the liquid in the flask. This arrangement permits the temperature to fall slowly so that large crystals are obtained. In the meantime a second conical flask containing 1250 cc. of toluene is attached to the funnel, and a new charge of 150 g. of crude methyl red is placed in the paper. When extraction is complete it is found that a certain amount of black amorphous insoluble matter remains on the filter; this is discarded. The crystals of methyl red are filtered off and washed with a little toluene. The weight of pure material is 755-805 g. The mother liquors are concentrated to one-fourth of their volume, and the crystals which separate on cooling are recrystallized from fresh toluene. The recovered toluene can, of course, be employed again. The total yield of pure methyl red is 790--840 g. It melts at 181-182'0. The watery mother liquors from the crude methyl red are rendered alkaline with sodium hydroxide and distilled until no more dimethylaniline passes over. In this way 250 to 400 g. of moist dimethylaniline are recovered. 2. Notes The amount of hydrochloric acid indicated must not be reduced; otherwise, diazoamino compounds are formed. It is essential to keep the temperature low while unreacted diazobenzoic acid remains in solution, in order to avoid decomposition. If this precaution is not taken, the yields are considerably diminished, through the formation of tarry by-products. The use of a capillary tube for the addition of sodium nitrite prevents loss of nitrous acid by local reaction at the surface of the acid solution. The tube should not be tightly connected to the dropping funnel, but should be so arranged that air is sucked through with every drop. In this way, the entrance of the acid liquor into the capillary is prevented.