23 ноября, 2015 
Pokraskin (Metanilic Acid, Naphthionic Acid, ISitroanilinetulfonic Acid,
Cldoroanilinemlfonic Acid, Diaminostilbenedimlfonic Acid,
Primulineeulfonic Acid, etc.)
A solution of sulfanilic acid, equivalent to 17.3 grams (0.1 mole) of 100 per cent material, in 100 cc. water containing 5.5 grams of soda (if the sulfonate is used instead of the free sulfonic acid, the soda is omitted, of course) is treated with 25 cc. concentrated hydrochloric acid and then, with good stirring, with 35 cc. 20 per cent sodium nitrite solution. The diazotization requires about 10 minutes, during which the temperature should not exceed 15°.
Diazo compounds which contain a sulfo group are usually quite insoluble and precipitate as white or yellow crystals of the inner salt. Since many of the aminosulfonic acids themselves are also relatively insoluble, it is desirable to diazotize them by the indirect method. This is done by adding the necessary amount of nitrite to the solution of the sodium sulfonate, and pouring the solution into the acid.
Further difficulties are sometimes encountered because certain amines tend to couple with themselves. Cleve acids are examples. An excess of about 5 per cent of sodium nitrite is required in diazotizing them.
Опубликовано в рубрике 