Abstract: The invention discloses a process for the preparation of azo dyes using an aminodiphenylamine as diazo component. The process comprises reacting the amine, an alkali metal nitrite and a mineral acid continuously in the temperature range from 35.degree. to 65.degree. C. to give the diazo compound, using a 3 to 15% excess of alkali metal nitrite, and thereafter coupling the diazo compound to a coupling component. Azo dyes of superior quality constancy and in high yield are obtained by the novel process.

Abstract: A process for the preparation of azo dyes of formula ##STR1## wherein K is the radical of a coupling component of the benzene or naphthalene series or of the heterocyclic series, and the hydroxy group is attached to K adjacent to the azo group, X is hydrogen or nitro and M is an alkali metal ion, which process comprises coupling a diazo component of formula ##STR2## in the presence of one or more buffer mixtures and in the absence or presence of an alkali metal chloride, to a coupling component of formula ##STR3## in which formulae (2) and (3) K and X are as defined for formula (1). The present invention makes it possible to prepare the azo dyes in high yields.

Abstract: A process for controlling and optimizing chemical industrial processes for the preparation of dyes, fluorescent whitening agents and their intermediates, which process comprises controlling and optimizing those processes by differential analysis of the UV/VIS absorption spectra of at least one starting compound and of at least one reaction product. The advantage of this process is that the actual state of a process can be constantly measured, assessed, and used for feed-back and feed-forward control.

Abstract: There is disclosed a process for coupling one or more different diazo components with resorcinol on an industrial scale. The process comprises adjusting and stabilizing the coupling pH of the resorcinol prior to the reaction with the aid of a buffer system and keeping it constant during the coupling reaction or reactions by controlling the ratio of flow of the streams of the diazo component or components and the base. The process makes it possible to prepare mono- and polyazo dyes in excellent uniform quality and yield.

Abstract: Process for the preparation of azo dyes of the formula ##STR1## in which K is the radical of a coupling component of the benzene or naphthalene series or of the heterocyclic series in which the hydroxyl group is attached to K in a position adjacent to the azo group, X is hydrogen or nitro and M is an alkali metal ion or ammonium ion, which comprises coupling a diazo component of the formula ##STR2## in the presence of an alkali metal chloride and ammonium chloride with a coupling component of the formula (3) ##STR3## K and X in the formulae (2) and (3) being as defined under formula (1). The present invention allows the preparation of the said azodyes in high yields.

Abstract: A process for the preparation of polyazo dyes is described which comprises(a) diazotizing a compound of the formula ##STR1## and coupling the product onto a compound of the formula ##STR2## (b) diazotizing a compound of the formula ##STR3## and coupling the product onto the product obtained according to (a); (c) diazotizing a compound of the formula ##STR4## and coupling the product onto the product obtained according to (b); (d) if desired, coupling of a further diazotized compound of the formula (3) onto the product obtained according to (c); and(e) if desired, metallizing the product obtained according to (c) or (d); and in which the symbols are as defined in claim 1. The polyazo dyes obtainable by the process are suitable for dyeing a wide range of textile and non-textile materials and, in particular, for dyeing leather.

Abstract: Polyazo dyes obtainable by(a) diazotizing 1-amino-8-hydroxynaphthalene-3,6-disulfonic acid and coupling onto a compound of the formula ##STR1## (b) coupling a diazotized compound of the formula ##STR2## onto the monoazo dye thus obtained, (c) coupling a diazotized compound of the formula ##STR3## onto the product obtained as per (b), and (d) if desired metallizing the product obtained as per (c), the symbols in the formulae being as defined in claim 1, are suitable for dyeing a wide range of textile and nontextile materials, in particular leather.