Bayer Aktiengesellschaft

Karl Linhart

Harald Gleinig

Gunther Boehmke

Roderich Raue

Hans-Peter Kuhlthau

Reinold Schmitz

Adolf Friedrich

Kurt Breig

Dieter Pawellek

Concentrated stable solutions of cationic azo dyestuffs of the formula ##STR1## wherein A denotes the radical of an aromatic-carbocyclic or aromatic-heterocyclic diazo component,

Process for the preparation of solutions of cationic azo dyestuffs

Concentrated, stable solutions, with a low salt content, of cationic azo dyestuffs of the formula ##STR1## wherein A denotes the radical of an aromatic-carbocyclic or aromatic heterocyclic diazo component,

Preparing concentrated azo dye solutions using nitrite salt as both

To prepare concentrated solutions of cationic polyazo dyestuffs of the formula ##STR1## in which R represents hydrogen or methyl and

Process for the preparation of solutions of cationic polyazo dyestuffs

Polynitrated diaryl compounds of the formula given in the description are reduced with 1-2 mols of sulphides, or compounds which donate sulphide ions, per mol of nitro group in the presence of 0.5-10 mols of ammonia per mol of starting compound at 30.degree.-110.degree. C. to give nitroamino-diaryl compounds, for example 4,4'-dinitro-dibenzyl-2,2'-disulphonic acid is reduced to 4-nitro-4'-amino-stilbene-2,2'-disulphonic acid.

Process for the partial reduction of polynitrated diaryl compounds

A process for the preparation of an amino-nitro-phenol by partial reduction of a polynitrophenol by contacting the polynitrophenol with an aqueous ammonia solution and a sulfide ion, the ammonia being present in an amount of 1 to 8 mols ammonia per mol of polynitrophenol and the sulfide being present in an amount of 2.5 to 6 mols sulfide ion per mol polynitrophenol, the process being conducted at a temperature of from room temperature to 100.degree. C.

Process for the preparation of amino-nitrophenols

1-Nitro-anthraquinone is separated from an anthraquinone nitration mixture in concentrated nitric acid by adding to the nitration mixture sulpholan and separating off the insoluble 1-nitro-anthraquinone. The quantity of sulpholan added is such that the mixture contains 10-90% by weight nitric acid and from 90-10% by weight sulpholan.

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Leverkusen, Germany

Karl Linhart