Fumaric acid N:N1 - di - (5 - hydroxy - 7-sulpho - 2 - naphthyl) - amide is prepared by condensing J acid with fumaric dichloride. A similar condensation product is made from 1 mol. each of fumaric dichloride, 2-amino-5-naphthol-7-sulphonic acid and 4-amino-41-nitrostilbene - 2:21 - disulphonic acid, the nitro group being subsequent reduced to amino.ALSO:The invention comprises (1) disazo and polyazo dyestuffs of the formula <FORM:0740715/IV(c)/1> where R1 and R2 are benzene, diphenyl, stilbene, naphthalene, pyrazolone or acetoacetylaminoaryl residues, one y is hydroxyl, the other y is hydrogen, w is hydrogen, halogen, alkyl, nitro, acylamino or sulphonic acid, one v is hydrogen, chlorine, bromine or methyl, the other v is hydrogen, n is O or I, and b is the residue a or a residue of a monoazo, disazo or trisazo compound of the benzene, naphthalene or pyrene series; (2) the preparation of disazo and polyazo dyestuffs by the following processes:-(a) condensing a dicarboxylic acid halide of the formula Z-CO-CA=CH-CO-Z (Z=chlorine or bromine, A=hydrogen, chlorine, bromine or methyl) with 2 mols of the same or different water-soluble aminoazo or aminodisazo compounds containing no metallisable grouping other than a terminal salicylic acid residue, or 2 mols of a mixture of such a compound and a non-metalizable aminoazo, aminodisazo or aminotrisazo compound; (b) tetrazotising a diamine of the formula NH2-R-NH-CO-CA=CH-CO-NH-R-NH2 (R=arylene residue) and coupling with an azo component (which may be substituted with further arylazo or diazotisable amino groups) snch that the product has at the most 5 azo groups, is water-soluble and contains no metallisable grouping other than a terminal salicylic acid residue; (c) a modification of (b) where a monoamine is diazotised and coupled, a nitro or acylamino group then converted into a second amino group and the latter diazotised and coupled; (d) coupling a dihydroxy compound of the formula HO-R3-NH-CO-CA=CH-CO-NH-R4-OH (R3 and R4= residues of azo components) with 2 mols of the same or different diazo compounds (which may contain further arylazo groups) such that the product satisfies the conditions set out in (b); (e) coupling one mol of a compound of the formula R5-NH -CO-CA=CH-CO-NH-R5 (R5 = aryl residue containing diazotisable amino group, one also containing a hydroxy group) with one mol of a diazo or diazoazo compound, diazotising and coupling with an azo component (which may be substituted with further arylazo or diazotisable amino groups), if desired carrying out further coupling reactions before or after diazotisation, the final product satisfying the conditions set out in (b); (f) a modification of (e) where R5 contains instead of the amino group a nitro or acylamino group, this being converted into amino for diazotisation. Processes (b)-(f) are carried out as in Specification 738,598. The invention however excludes the dyestuffs of the parent Specification and also those containing the (methylpyrazonyl) - stilbene disulphonic acid residue of Specification 726,726. If two different aminoazo compounds are used in method (a) the product will be a mixture of one asymmetrical and two symmetrical dyestuffs; the compounds may be used in any ratio from 4 : 1 to 1:4. The products of the invention are suitable for dyeing and printing cotton and regenerated cellulose and can be metallised in the dyebath or on the fibre. In examples the following are condensed with dicarboxylic acid halides according to method (a):-(1) 5-aminosalicylic acid --> aniline and 5-amino-3-sulphosalicylic acid --> cresidine, N-(p-aminobenzoyl) derivative; (2) mixture of latter and corresponding m-aminobenzoyl derivative; (3) 5-(41-amino - 31 - methylbenzoylamino) - 3 - sulphosalicylic acid--> m-toluidine and 5-amino-3-sulphosalicylic acid--> aniline; (4) 2 mols of 4 : 41-diaminostilbene-2 : 21-disulphonic acid--> (one side only)-salicylic acid; (5) 2 mols of 5-aminosalicylic acid--> m-chloraniline; (6) 3-(p-aminobenzoylamino)-5-sulphosalicylic acid --> m-toluidine and sulphanilic acid --> orthanilic acid --> m-toluidine; (7) salicylic acid \sM 4-(p-aminobenzoylamino)-aniline--> N-(p-aminobenzoyl)-J acid and 5-aminosalicylic acid --> aniline; many other suitable pairs of components are mentioned; including 2 monoazo, monoazo+disazo, 2 disazo and disazo+trisazo. In further examples, (8) fumaric acid di[p-(31-sulpho-41-aminophenyl)-anilide] is tetrazotised and coupled with 2 mols of 5-aceoacetylamino-salicylic acid; the 3-sulpho-4-amino-anilide may be used and other coupling components are mentioned; (9) N : N1-bis-fumaryl-J acid is coupled with 2 mols of diazotized 3-(p-aminobenzoylamino)-5-sulphosalicylic acid; (10) the reduced condensation product of fumaric dichloride with 1 mol of J acid and 1 mol of 4-amino-41-nitrostilbene-2 : 21-disulphonic acid is coupled with diazotised 3-(p-aminobenzoylamino)-5-sulphosalicylic acid; the product is then diazotised and coupled with 1-phenyl-3-methyl-5-pyrazolone. An additional example describes the dyeing of cotton with the product of (1), after-coppered. Suitable dicarboxylic acid halides are the dichlorides and dibromides of fumaric, maleic, mesaconic, citraconic, chlorofumaric and bromofumaric acids. In example (3) above there is used a mixture of fumaric and maleic dichlorides.