Abstract: The invention relates to a method of determining and controlling the diazonium ion concentration in diazotization solutions and/or in azo coupling reactions, which comprises determining said diazonium ion concentration by means of IR spectroscopy from the intensity of the N.tbd.N stretching frequency.The method is extremely selective and virtually trouble-free and permits the simultaneous determination of the concentration of different diazonium salts in mixtures.

Abstract: New inclusion compound, intercalation compounds or solid solutions which are the nickel salts or nickel complexes of a compound which, in one of its tauteromeric structures, corresponds to the formula ##STR1## which contain at least one other included compound, except for one composition of matter which consists of 45 to 82% by weight of azobarbituric acid/nickel 1:1 complex, 3 to 15% by weight of benzene-sulphonamide, 5 to 20% by weight of nickel acetate and 10 to 20% by weight of water and the use of these materials as pigments are disclosed.

Abstract: A process for pigmenting high molecular weight organic material, which comprises using, as pigment, a monoazo compound of the formula ##STR1## wherein A is a carbocyclic aromatic radical, R is an aliphatic, cycloaliphatic, araliphatic or aromatic radical or an alkoxy group, and Q is a hydrogen or a halogen atom or a methyl group.The colorations obtained, for example in plastics, filaments, lacquers and prints, have very high color strength, high saturation, good dispersibility, good fastness to overspraying, migration, heat, light and atmospheric influences, and good gloss.

Abstract: A process for the production of an azo compound comprising contacting with agitation a solution or dispersion of a diazotizable amine, a solution or dispersion of a coupling component and an organic or inorganic nitrite compound, in a water insoluble liquid organic acid, adding to the reaction mixture so formed aqueous alkali to transfer the organic acid, as its soluble salt, into the aqueous phase and separating the azo compound from the liquors.The azo compounds are produced in high yield and purity and are suitable for use as pigments and disperse dyes.