Abstract: 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,R denotes alkylene,R.sub.1 denotes hydrogen or alkyl,R.sub.2 denotes alkyl, alkenyl or aralkyl,R.sub.3 denotes alkyl,R.sub.4 denotes hydroxyalkyl with 2 or more C atoms,R.sub.5 denotes halogen, alkyl, alkoxy, aryloxy, acyl or acylamino,m denotes 0, 1, 2, 3 or 4 andAn .sup.(-) denotes a carboxylate ion,and wherein the cyclic and acyclic substituents can carry further non-ionic substituents, which solutions have a low salt content, are prepared by simultaneously reacting amines of the formulaA--NH.sub.2 (II)coupling components of the formula ##STR2## and alkali metal nitrites or alkaline earth metal nitrites in aqueous carboxylic acids and, if appropriate, organic water-soluble solvents, and then separating off the alkali metal sulphates or alkaline earth metal sulphates which thereby crystallize out.

Abstract: 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,R denotes alkylene,R.sub.1 denotes hydrogen or alkyl,R.sub.2 denotes alkyl, alkenyl or aralkyl,R.sub.3 denotes alkyl,R.sub.4 denotes hydroxyalkyl having 2 or more C atoms,R.sub.5 denotes halogen, alkyl, alkoxy, aryloxy, acyl or acylamino,m denotes 0, 1, 2, 3 or 4, andAn.sup.- denotes a carboxylate ion,and whereinthe cyclic and acyclic substituents can carry further non-ionic substituents,are prepared by the reaction of amines of the formulaA-NH.sub.2with coupling components of the formula ##STR2## in aqueous carboxylic acids and, if appropriate, organic water-soluble solvents.

Abstract: Leather dyeing agents, which can be obtained by concentrating, by means of a membrane separation process, the mother liquors, which are produced in the salting-out process in the preparation of organic dyestuffs which are water-soluble or which contain groups imparting water-solubility, the mother liquors having an extinction in the absorption maximum which is .gtoreq.500, with a layer thickness of 10 cm, and by drying the concentrate, if appropriate.

Abstract: To prepare concentrated solutions of cationic polyazo dyestuffs of the formula ##STR1## in which R represents hydrogen or methyl andR.sup.1 represents an alkyl radical which has 1 to 3 carbon atoms and is optionally substituted by hydroxyl, alkoxy or halogen,and mixing coupling products thereof with aromatic monoamines, diaminobenzenes of the general formula ##STR2## in which R has the abovementioned meaning,if appropriate mixed with up to 30 mol % of aromatic monoamines of the formula ##STR3## in which R.sup.2 represents hydrogen, C.sub.1 - to C.sub.4 -alkyl, C.sub.1 - toC.sub.4 -alkoxy or C.sub.1 - to C.sub.4 -acylamino andn denotes a number from 1 to 3,are dissolved in aliphatic carboxylic acids which have 2 to 4 carbon atoms and can optionally be substituted by halogen, hydroxyl or alkoxy, and are reacted with 0.5 to 0.75 mol of a salt or ester of nitrous acid per mol of diamine at 0.degree. to 30.degree. C.

Abstract: 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.

Abstract: Pulverulent preparations with a low dust content, in particular dyestuff powders, are obtained when the customary dustproofing agents are not added before the drying process and also are not sprayed directly onto the product to be dustproofed, but are allowed to act on the pulverulent product in the form of an aerosol.The average particle size of the aerosol is less than 10.mu..

Abstract: Cationic dyestuffs of the general formula ##STR1## wherein R.sub.1 represents hydrogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 - to C.sub.4 -alkoxy, nitro or halogen,R.sub.2 represents hydrogen, C.sub.1 - to C.sub.4 -alkyl, C.sub.1 - to C.sub.4 -alkoxy, halogen or phenylazo,R.sub.3 represents C.sub.1 - to C.sub.3 -alkyl andA.sup..crclbar. represents an anion,are prepared by reacting azo bases of the general formula ##STR2## wherein R.sub.1 and R.sub.2 have the abovementioned meaning, or the salts thereof with inorganic or organic acids, with dialkyl sulphates of the general formula(R.sub.3 --O--).sub.2 SO.sub.2 IIIwherein R.sub.3 has the abovementioned meaning, in the absence of organic solvents and in the presence of water, the weight ratio of azo base to water being 100:20-300 and the molar ratio of azo base to dialkyl sulphate being 1:3.5-5.0, and, if desired, by replacing the alkyl-sulphate anion with another anion.

Abstract: Cationic dyestuffs of the general formula ##STR1## wherein R.sub.1 represents hydrogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 - to C.sub.4 - alkoxy, nitro or halogen,R.sub.2 represents hydrogen, C.sub.1 - to C.sub.4 -alkyl, C.sub.1 - to C.sub.4 -alkoxy, halogen or phenylazo,R.sub.3 represents C.sub.1 - to C.sub.3 -alkyl andA.crclbar. represents an anion,are prepared by reacting azo bases of the general formula ##STR2## wherein R.sub.1, R.sub.2 and R.sub.3 have the abovementioned meaning, with dialkyl sulphates of the general formula(R.sub.3 --O--).sub.2 SO.sub.2 (III)wherein R.sub.3 has the abovementioned meaning, in the absence of organic solvents and in the presence of water, the weight ratio of azo base to water being 100:15-100 and the molar ratio of azo base to dialkyl sulphate being 1:1.5-2.5, and, if desired, by replacing the alkyl-sulphate anion with another anion.

Abstract: The preparation of hydrazone dyestuffs of the formula ##STR1## wherein R.sup.13 and R.sup.14 independently of one another represent hydrogen, C.sub.1 -- to C.sub.4 --alkyl, C.sub.1-- to C.sub.4-- alkoxy or halogen, in particular chlorine or bromine, andA.sup.- denotes an anionic radical,by reacting azo bases of the general formula ##STR2## wherein R.sup.13 and R.sup.14 have the above mentioned meaning andR.sup.15 represents hydrogen or the methyl group, with dimethyl sulphate in a mixture of water and an organic solvent and in the presence of an acid-binding agent, is characterized in that (a) aromatic or aliphatic chlorinated hydrocarbons are used as the organic solvents, (b) the reaction is carried out at a temperature of 10.degree.-60.degree. C., (c) a 5-90% excess of dimethyl sulphate is employed and (d) the reaction is allowed to proceed at a pH of 5-10.