Azo dyes, chromium compounds of; dye mixtures; acid wool dyes, dyeing with.--Chromiferous dyestuffs are obtained by the action of an alkaline chromium oxide solution on a mixture of chromable monoazo dyes of which at least one is of the general formula <FORM:0434835/IV/1> wherein R1 is a naphthalene residue, R2 is a naphthol residue, n is 1, 2 or 3 and the OH group is in o-position to the azo group, the amount of chromium oxide being sufficient to provide at least one atom of chromium for each chromable group in the dyestuffs. The chroming and the production of the dyestuffs may be effected in a single operation. The chromable mono-azo dyes not of the above general formula may be, for example, those obtainable by coupling a diazotized aromatic amine of the benzene or naphthalene series with an arylamine, phenol, pyrazolone, oxyquinoline, barbituric acid, acetoacetic acid derivative or benzoylaceto-o-carboxylic acid derivative. The chromiferous products are suitable for dyeing animal fibres, e.g. wool and silk, wool being conveniently dyed by the processes of Specifications 364,148 or 408,497. The following examples are specified. (1) A mixture of the dyestuff, 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol, with the dyestuff from the nitrated diazo compound of 1 : 2-aminonaphthol - 4 - sulphonic acid and 2 - naphthol is stirred into a solution of a freshly precipitated chromium hydroxide paste in 90 per cent caustic potash and the mixture is heated for 10--12 hours at 75--78 DEG C. and for a further 2--3 hours at 80--85 DEG C.; the whole is then diluted, mineral acid is added until the reaction is feebly alkaline and the dyestuff is salted out; alternatively, the 2-naphthol may be dissolved in the chromite solution, the diazotized 1 : 2-aminonaphthol-4-sulphonic acid introduced at 20 DEG C. and the nitrated diazotized 1 : 2 - aminonaphthol - 4 - sulphonic acid at 0--5 DEG C.; the product gives fast navy blue dyeings on wool from an acid bath. (2) 2 - Naphthol is dissolved in a solution of chromium hydroxide in 90 per cent caustic potash, the solution is cooled to 10--15 DEG C., a paste of diazotized 1 : 2-amino-naphthol - 4 - sulphonic acid is added with cooling to 8--10 DEG C. and further addition of a neutral solution of diazotized 4-methyl-2-aminophenol-5-sulphonic acid and the mixture is then heated for 12 hours at 74--78 DEG C. and for a further 4 hours at 80--85 DEG C.; the mixture is then diluted and neutralized and the dyestuff is salted out; the product gives reddish navy blue dyeings on wool from a sulphuric acid bath. (3) Wool is dyed a very fast navy blue by handling it for 10--15 minutes in dilute sulphuric acid at 60 DEG C., adding a solution of the dyestuff of (1), maintaining the bath at 60 DEG C. for 30 minutes, raising gradually to the boil, adding more sulphuric acid and boiling for 30--45 minutes. (4) Wool is dyed a fast dark navy blue by handling it for 10 minutes in dilute formic acid at 85--90 DEG C., adding a solution of the dyestuff of (1), boiling, adding more formic acid, boiling for 20--30 minutes, adding sulphuric acid and boiling for 30 minutes, adding more sulphuric acid gradually and boiling for 75--90 minutes. (5) Wool is dyed a fast reddish navy blue by entering it into a solution at 60--70 DEG C. of the dyestuff of (2) in dilute sulphuric acid with an addition of benzenesulphonic acid or its sodium salt, raising the temperature to the boil during 30 minutes and continuing to boil for 60--75 minutes. (6) Ordinary or loaded silk is dyed a fast reddish navy blue by entering it into a solution at 50--60 DEG C. of the dyestuff of (2) in dilute acetic acid, heating the bath gradually to 80 DEG C. and maintaining this temperature for 45--60 minutes. The samples furnished under Sect. 2 (5) are of chromed dyestuffs from mixtures of (a) the dyestuffs 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol and 2 : 1-aminonaphthol-4-sulphonic acid --> 2-naphthol; (b) the dyestuffs 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol and 4-chloro-2-aminophenol --> 1 : 8-dioxynaphthol-3 : 6-disulphonic acid; (c) the dyestuff 1 : 2-aminonaphthol-4-sulphonic acid --> 1-naphthol and the dyestuff from the nitrated diazo compound of 1 : 2-aminonaphthol-4-sulphonic acid and 2-naphthol; (d) the dyestuffs 1 : 2-aminonaphthol-4-sulphonic acid --> 1-naphthol and 4-methyl-2-aminophenol --> 2-naphthol; (e) the dyestuffs 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol and 2-aminophenol-4 : 6-disulphonic acid-->1-phenyl-3-methyl-5-pyrazolone; (f) the dyestuffs 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol, 4-chloro-2-aminophenol --> resorcinol and 4 - nitro - 2 - aminophenol - 6-sulphonic acid --> 2-naphthol; (g) the dyestuff from the nitrated diazo compound of 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol and the dyestuffs 2-aminophenol-4-sulphamide --> 1-(3<1>-sulphophenyl)-3-methyl-5-pyrazolone and 4-nitro-2-aminophenol-6-sulphonic acid --> acetoacetanilide; (h) the dyestuffs 1 : 2-aminonaphthol-4-sulphonic acid and 2-naphthol, 2 - aminophenol - 4 : 6 - disulphonic acid --> 1-phenyl-3-methyl-5-pyrazolone and 4-nitro-2-aminophenol-6-sulphonic acid --> 1-phenyl-3-methyl-5-pyrazolone; (i) the dyestuffs 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol and 2 : 1-aminonaphthol-4-sulphonic acid --> 2-naphthol, in proportions differing from those in (a) above; (j) the dyestuff from the nitrated diazo compound of 1 : 2-aminonaphthol-4-sulphonic acid and 2-naphthol and the dyestuffs 4 - nitro - 2 - aminophenol - 6 - sulphonic acid --> acetoacetanilide and 4-nitro-2-aminophenol-6-sulphonic acid --> 1-phenyl-3-methyl-5-pyrazolone; (k) the dyestuff from the nitrated diazo compound of 1 : 2-aminonaphthol-4-sulphonic acid and 2-naphthol, the reduction product of the same and the dyestuff 4-chloro-2-aminophenol-5-sulphonic acid --> barbituric acid; (l) the dyestuffs 1 : 2-aminonaphthol-4-sulphonic acid --> 1-naphthol and 4-methyl-2-aminophenol-5-sulphonic acid --> 2-naphthol. Reference has been directed by the Comptroller to Specification 297,331, [Class 2 (iii)].