Лако-красочные материалы — производство

Xylene blue belongs to the group of so-called patent blues which are sulfonated triphenylmethane dyes that are stable to alkali. The dyes are all characterized by having a sulfo group in the position ortho to the central carbon atom as in the following general formula:

s

Na

Sandmeyer first explained the relation between structure and alkali stability, and his erioglaucine was the first dye prepared to take advan­tage of this relationship.

Erioglaucine A

from ethylbenzylanilinesulfonic acid
and o-sulfobenzaldehyde

Apparently an inner anhydride is formed between the carbinol hy­droxyl and the sulfo group, and this causes the stability toward soda and caustic alkali. This assumption appears probable because dyes of the type below are entirely insoluble:

‘ (c)

—SOjH/ —CH[C6H4′ N(C1HS)1], —►

~!SO, H

Leuco xylene blue VS Xylene blue VS

To 46 grams (0.5 mole) of pure, boiling toluene is added, over a period of 15 minutes, 80 grams of 100 per cent sulfuric acid, and the mixture is heated at 125°C. for 1 hour. During this time the toluene dis­appears completely. The mixture is cooled to 30°, and 220 grams of 66 per cent oleum is added with thorough stirring over a period of 30 minutes. The solution is then heated for 4 hours at 125°, converting all of the toluene to the disulfonic acid. The mixture is diluted with 400

grams of sulfuric acid (66° Be) and transferred to a porcelain beaker set up with an efficient iron stirrer.