Preparation
the molecular than 2-Amino-5-(4-nitroanilino)benzenesulfonic acid, 3-(Ethyl(phenyl)amino)methyl)benzenesulfonic acid, 2-Aminobenzenesulfonic acid with heavy chromium acid potassium and sulfuric acid oxidation, then use 4-Aminobenzenesulfonic acid further oxidation, reduction with the iron powder.
Synthesis
Neutral solutions containing the sodium salt of 61 kg of 4-nitro-4- aminodiphenylamine-2-sulfonic acid in 500 L ofwater and the sodium salt of 57 kg of N-ethyl- N-benzylanilinesulfonic acid in 300 L water are combined in a 5000 L wooden vat equipped with a propeller stirrer. After the solution has been diluted with 1400 L of ice water, a solution containing 75.5 kg of sodium dichromate and 37.2 kg of sulfuric acid monohydrate in 4000 L water is added at 5 ℃. After stirring the mixture for 15 min, a neutral solution containing the sodium salt of 30.5 kg of aniline-4-sulfonic acid in 290 L of water is added. The mixture is again stirred for 15 min, then heated to 40 ℃ and stirred for 15 min. After rapid heating of the mixture to 80 ℃ with live steam, 11 kg of sodium carbonate is added. The reaction mixture, cooled to 70 ℃, is transferred to a 6000 L reduction vessel equipped with a propeller stirrer, mixed with 50 kg of iron filings, and stirred for 45 – 60 min.
The alkaline spot test must show a brown rather a reddish blue spot. The reaction mixture is allowed to settle, then filtered through a filter press. The process of settling and filtration is repeated and the press is then washed, first with 1000 and then with 2000 L of water. The filtrate is salted out with 800 – 850 kg of common salt and, after stirring overnight at 18 – 20 ℃, filtered under suction. After drying under vacuum, 180 – 190 kg of the dye is obtained, corresponding to 360 – 380 kg of commercial-type Acid Cyanine BF.
