Abstract: The invention relates to a new process for the preparation of 1-aminonaphthalene-2,4,7-trisulphonic acid and 1-aminonaphthalene-7-sulphonic acid (1,7-Cleve's acid), in which 1-aminonaphthalene or naphthionic acid is sulphonated selectively in the presence of certain additives to give 1-aminonaphthalene-2,4,7-trisulphonic acid and this is hydrolyzed to 1,7-Cleve's acid by warming in aqueous sulphuric acid.

Abstract: Solid crystalline tetra-alkali metal salts of chromotropic acid, a process for their isolation and their use for the preparation of pure chromotropic acid or di-alkali metal salts of chromotropic acid.

Abstract: The invention relates to a process for the preparation of 1-amino-8-naphthol-4,6-disulphonic acid (K-acid) as the mono-alkali metal salt by reacting a mixture of naphthylaminetrisulphonic acids and/or salts thereof with an alkali metal salt solution and separating the K-acid as the mono-alkali metal salt, by acidification and crystallization. The product is a known valuable dyestuff intermediate.

Abstract: A process for the preparation of 5-amino-2,4-dimethylacetanilide by reduction of 5-nitro-2,4-dimethylacetanilide with hydrogen is disclosed characterized in that a crude mixture containing 5-nitro-2,4-dimethylacetanilide in admixture with at least one of its position isomers is hydrogenated in a water-miscible organic solvent which optionally contains water. The 5-amino-2,4-dimethylacetanilide is separated off from the reaction mixture by means of crystallization employing a mixture of water-miscible organic solvent and water.

Abstract: 4-Hydroxydiphenyl (mono-OD) and 4,4'-dihydroxydiphenyl (DOD) are obtained simultaneously from a mixture which contains these two substances, if such a mixture is treated with an aqueous alkali, and the resulting solution and the solid phase formed are separated at a temperature from -28.degree. C. to +40.degree. C. and the solution and the solid phase are acidified separately in order to form the free mono-OD and DOD. Mono-OD and DOD can be present in the starting mixture in the free form or in the form of the alkali metal phenolates. After formation of the alkali metal phenolates, where this is required, the aqueous alkali still contains 1-15 mol of alkali metal hydroxide per mol of the diphenyl compounds. The concentration of alkali metal hydroxide should be 4-25% by weight, relative to the amount of water present. In this process, it is also possible to employ industrial mixtures of the alkali melts of the associated diphenyl-sulphonic acids.

Abstract: Improved process for the preparation of nitronaphthalene-sulphonic acids by reacting the corresponding naphthalene-sulphonic acids with nitric acid and working up the nitration mixture, characterized by the features that the reaction of the naphthalene-sulphonic acids with nitric acid is already interrupted before the nitration reaction has ended and that the nitration mixture is treated, optionally after dilution with water, with bases at a pH value of 5 to 14.

Abstract: A process for the preparation of o-nitrobenzaldehyde, comprising converting to the corresponding acetals a mixture of nitrated benzaldehyde which contains about 10 to 30% of o-nitrobenzaldehyde and about 70 to 90% of m-nitrobenzaldehyde, removing the o-nitrobenzaldehyde acetal by distillation, and then converting the o-nitrobenzaldehyde acetal to o-nitrobenzaldehyde.

Abstract: The process for preparing 1-amino-2-naphthol-4-sulphonic acid by acidifying 3-oxo-4-hydroxyimino-1,2,3,4-tetrahydronaphthalene-1-sulphonic acid or its alkali metal salt in the presence of hydrogen sulphite is carried out in the presence of iron ions.

Abstract: The invention relates to a process for the preparation of 1-benzoylamino-8-hydroxynaphthalene-4,6-disulphonic acid (benzoyl-K acid) by reacting 1-amino-8-hydroxynaphthalene-4,6-disulphonic acid (K acid) with benzoylating agents, according to which process mixtures of aminonaphtholdisulphonic acid isomers are used instead of pure K acid, which mixtures contain over 40% by weight of K acid, relative to the total amount of diazotizable compounds in the mixture of isomers, and in which no other single isomer has a proportion which exceeds 10% by weight of the total amount of diazotizable compounds in the mixture of isomers.

Abstract: The invention relates to a process for isolating H acid and K acid in the form of their monoalkali metal salts from acid aqueous solutions which contain these two acids and alkali metal ions and may contain other aminonaphtholdisulphonic acids, in which process H acid monoalkali metal salts are precipitated at elevated temperatures from solutions which contain not only sodium ions but also potassium ions and then precipitating K acid monoalkali metal salts by cooling down the filtrate obtained after separating off the H acid monoalkali metal salts.

Abstract: Process for the isolation of 1-naphthylamine-4,8-disulphonic acid from sulphonation mixtures containing it according to which process the sulphonation mixture is introduced into preheated water in such a manner that, at the start of crystallization, a temperature of at least 100.degree. C. is reached and the 1-naphthylamine-4,8-disulphonic acid is separated from the mother liquor at a temperature not higher than 70.degree. C. The process is applied particularly advantageously for the isolation of 1-naphthylamine-4,8-disulphonic acid from sulphonation mixtures which have been obtained by introducing in turns alkali metal sulphate, 1-naphthylamine-8-sulphonic acid and SO.sub.3 into sulphuric acid which has been introduced initially, a total of 1.5 to 3 mols of SO.sub.3 and 0.6 to 1.5 mols of alkali metal sulphate being employed per mol of 1-naphthylamine-8-sulphonic acid.

Abstract: A process has been provided for the preparation of nitro-T-acid by nitration of naphthalene-1,3,6-trisulphonic acid from a nitration mixture which has reacted to the extent of at least 80% which naphthalene-1,3,6-trisulphonic acid or a mixture containing the latter. Nitro-T-acid (and T-acid) is an intermediate for the preparation of H-acid which, in turn, is an intermediate for the preparation of dyestuffs.

Abstract: A process is provided for the preparation of naphthalene-1,3-5,-trisulphonic acid from 1,5-disulphonated naphthalene, which comprises sulphonating 1,5-disulphonated naphthalene, in the form of a mixture which has been obtained by mixing naphthalene and SO.sub.3 in the presence of an inert solvent at temperatures in the range of -40.degree. to +20.degree. C., the ratio of SO.sub.3 added to naphthalene added having been in the range of 2.5 to 10 mols of SO.sub.3 per mol of naphthalene during the entire addition, at 60.degree. to 110.degree. C. in anhydrous sulphuric acid with oleum, with prior or concurrent separation of the inert solvent.The resulting product is a known intermediate for the formation of azo dyestuffs.

Abstract: Process for the isolation of 1-naphthylamine-4,6- or 1-naphthylamine-4,7-disulphonic acid from sulphonation mixtures obtained in the sulphonation of 1-naphthylamine-6- or 1-naphthylamine-7-sulphonic acid with sulphuric acid and sulphur trioxide, wherein the aqueous solutions or suspensions formed, when the sulphonation mixtures are introduced into water, are warmed to 80.degree. to 120.degree. C., optionally kept for a period of time at this temperature, are then cooled to temperatures below 70.degree. C., and the 1-naphthylamine-4,6- or 1-naphthylamine-4,7-disulphonic acid which has crystallized out is finally filtered off.

Abstract: A process for producing the magnesium salt of 3-nitro-naphthalene-1,5-disulfonic acid by sulfonating naphthalene, nitrating the sulfonation product, and separating the pure magnesium salt of 3-nitronaphthalene-1,5-disulfonic acid, which process comprises:(a) sulfonating naphthalene with liquid SO.sub.3 in the presence of an inert organic solvent at temperatures between -40.degree. and +20.degree. C.

Abstract: Improved process for the preparation of 1-naphthylamine-4,6-disulphonic acid wherein the sulphonation of the 1-naphthylamine-6-sulphonic acid is carried out by adding the oleum at a temperature of 10.degree. to 70.degree. C., either to initially introduce sulphuric acid simultaneously with the 1-naphthylamine-6-sulphonic acid or to 1-naphthylamine-6-sulphonic acid, which is dissolved or suspended in sulphuric acid, and by using such a molar ratio of sulphur trioxide to 1-naphthylamine-6-sulphonic acid that 1.2 to 3 mols of sulphur trioxide are present per mol of 1-naphthylamine-6-sulphonic acid. The sulphonation mixture formed in the preparation can be sulphonated in a second sulphonation stage to 1-naphthylamine-2,4,6-trisulphonic acid.

Abstract: The invention relates to a process for the preparation of 1-amino-8-naphthol-3,6-disulphonic acid (H-acid) as the mono-alkali metal salt from napthylamine-trisulphonic acid isomer mixtures by alkaline hydrolysis under pressure. The separation of the H-acid is effected by utilizing an aqueous sulphuric acid which contains naphthalene- and/or nitronaphthalene- and/or naphthylamine- and/or naphthol- and/or aminonaphthol-mono-, -di-and/or-tri-sulphonic acids.

Abstract: A process has been invented for the preparation of naphthalene-1,3,6-trisulphonic acid by sulphonating naphthalene with sulphuric acid and oleum, characterized in that naphthalene and most of the oleum are simultaneously metered into sulphuric acid or oleum of low concentration, which has been initially introduced, at about 140.degree. to 240.degree. C., the temperature is kept at about 140.degree. to 240.degree. C. for some time, the remainder of the oleum is then added at about 140.degree. to 240.degree. C. and the mixture is then further stirred for some time.Naphthalene-1,3,6-trisulphonic acid is a known important intermediate used, for example, in the preparation of T-acid, H-acid and chromotropic acid.

Abstract: A process has been invented for the preparation of a mono-alkali metal salt of 1-amino-8-naphthol-3,6-disulphonic acid comprising reacting 1-naphthylamine-3,6,8-trisulphonic acid and/or a salt thereof and/or a naphthylamine-trisulphonic acid isomer mixture and/or salt thereof with an alkali metal hydroxide solution at elevated pressure and elevated temperature and in the presence of an alcohol or alcoholate, and separating out the mono-alkali metal salt by acidification. The process results in the procurement of higher yields of the desired product and in the formation of less by-products.

Abstract: A process has been invented for the preparation of a mono-alkali metal of 1-amino-8-naphthol-3,6-disulphonic acid, comprising reacting 1-naphthylamine-3,6,8-trisulphonic acid and/or a salt thereof and/or a naphthylamine trisulphonic acid isomer mixture and/or salt thereof with an alkali metal hydroxide solution in the presence of an alcohol and/or alcoholate and in the presence of a substance which contains at least one oxygen atom bonded to a nitrogen atom, at elevated pressure and elevated temperature, and separating out the mono-alkali metal salt of 1-amino-8-naphthol-3,6-disulphonic acid by acidification. The process results in the procurement of higher yields of the desired product and in the formation of less by-products.