Pararosaniline, production

Rosaniline or magenta was originally obtained by oxidising with arsenic acid a mixture of aniline with 0- and />-toluidine. The product was then lixiviated and treated with common salt, which converted the ai senate into the hydrochloride of rosaniline. Pararosaniline was prepared in a similar way fiom a niixtuie of aniline and /-toluidine. The series... 

It is prepared by air oxidation of dimethylaniline in the presence of phenol and copper salts as well as sodium chloride. The reaction product consists of tetra- to hexamethylated pararosanilines (see 119, p. 541) ... 

Two years later Hofmann [3] announced the discovery of a red product, obtained by the action of carbon tetrachloride on aniline. Hofmann and Nathanson, if their experiments were made with pure aniline, must have already had pararosaniline in their hands. 

The commercial product is a mixture, consisting chiefly of pentamethyl- and tetramethyl-pararosaniline with some hexa-methylpararosaniline. 

Another blue is obtained by the action of aniline and benzoic acid on pararosaniline. This product is valued for the pure greenish shade which it produces, and it has recently found extensive application, and appears to have almost displaced diphenylamine blue. 

The method of Fan and Dasgupta (1994) relics on tlie reaction of formaldehyde with 1,3-cyclohexane-dione in acidified ammonium acetate to form the fluorescent dihydropyridine derivative in a flow injection analysis system. Formaldehyde trapped in water can be reacted with pararosaniline and sodium sulfite under mild conditions (neutral pH, room temperature equilibration) to produce a colored product that is measured at 570 nm (Petreas et al. 1986). The presence of bisulfite is an interference in this reaction so the method cannot be used to sample atmospheres that contain sulfur dioxide. In addition, the method is reported to suffer from interferences resulting from the presence of other aldehydes and phenol (Hoogenboom et al. 1987). The indirect method of Hoogenboom et al. (1987) relies on the reaction of excess bisulfite in an aqueous solution of formaldehyde with 5,5 -dithiobis(2-nitrobenzoic acid) to form a colored product, the absorbance of which is measured at 412 nm. The method reported by Naruse et al. (1995) relies on the formation of a colored product obtained by reacting the aqueous formaldehyde with acetylacetone and ammonium acetate in acetic acid. Absorbance is measured at 414 nm. 

Each of these products was conditioned at room temperature, and 100% relative humidity (RH) (31 to 67 days). Formaldehyde release was measured as described H, 8, 15). A modified JIS desiccator procedure was used, and formaldehyde was quantitated using a pararosaniline procedure (15, 16). Formaldehyde release rate coefficients were calculated (15). An average coefficient of variation of 16% was obtained for this measurement (15). Samples displaced less than 12% of the chamber air (15). 

Procedure Formaldehyde sample from the sampler was injected into the carrier stream where it was mixed with pararosaniline and then sulfite to form an alkylsulfonic acid chromophore which can be monitored spectrophotometrically at 570 nm For calibration, standard formaldehydes were sequentially introduced after a stable baseline was obtained At least five consecutively reproducible peaks were recorded for each concentration After each study or each day of operation, the FIA system was cleaned to remove any pararosaniline film, alkylsulfonic acid colored product, or particulate matters This reduced the scattered light in the absorption cell and the staining of the tubing walls. The clean-up procedure was initiated by running distilled deionized water through the system for five minutes followed by another five minutes washing with 0 1 N nitric acid and then flushing the unit for 30 minutes with deionized water The chromotropic acid method was used for comparative studies, and the analytical procedure for the chromotropic acid method was based on the procedure recommended by the American Public Health Association (12) ... 

In some methods the colour system is a product of a synthesis reaction. Examples of such methods are formation of an indophenol dye in a method for determination of ammonia, the synthesis of azo dyes in the determination of nitrite, the formation of Methylene Blue in the determination of sulphur, the pararosaniline method for determination of sulphite, and the benzidine-pyridine method for determination of cyanide. 

In strongly acidic media, pararosaniline (hydrochloride) exists as a colourless species. The reaction of colourless pararosaniline with hydroxymethanesulphonic acid gives a purple compound which is the basis of this sensitive spectrophotometric method for determining SO2, sulphite, or any other form of sulphur converted into SO2 [21-24]. The coloured reaction product has the formula ... 

The rosanilins are powerful triacid bases, are colorless, but combine with acids to form brilliantly colored salts. Fuchsine is industrially obtained from anilin oil, which contains both anilin and toluidin, neither of which in the pure state will produce a red color. The process consists essentially in heating the-oU with a mixture of nitro-benzene, hydrochloric acid and iron filings. The product is a mixture of the chlorids of rosanilin and pararosanilin, is in hard, green crystals, soluble in water and alcohol, to which it communicates a brilliant red color. 

The electron-cytochemical method for localization of DPP was optimized by Lojda (1981) and its modification for cytochemical reaction for DPP in glutaraldehyde prefixed yeast cells was described recently (Voffsek in preparation). In principle, the synthetic dipeptide substrate has its carboxyl terminus bound to 4-methoxy-2-naphthylamine. The primary reaction product was formed by coupling hexazonium pararosaniline (HPR) with the MNA liberated by DPP and was osmiophilic. Thus postfixation by osmium tetrox-ide revealed also the electron-dense final reaction product on the background of the general osmiophilia of the matrix phase and membranes. 

Basic Red 9 (Pararosaniline) is the simplest triphenylmethane dye. It is prepared by the condensation of one mole of p-toluidine and two moles of aniline, usually by heating in nitrobenzene, which serves as solvent and oxidant. The first product is a colorless carbinol, which is converted to the dye with hydrochloric acid. 

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