Uniformly pigmented copolymers of conjugated dienes are prepared by mixing an organic pigment or carbon black with water, adding a composite surface-active agent as hereinafter defined so producing a substantially non-settling finely-divided and uniform suspension of pigment particles free from Brownian movement, mixing the suspension with a rubber latex, coagulating the mixture with a coagulating agent and isolating the resulting pigmented rubber. In the case of carbon black, the suspension of carbon in water may be formed by adding to the water, carbon black pellets containing the composite surface-active agent. This surface-active agent comprises a dispersing agent which is a naphthalene sulphonic acid-formaldehyde condensate, a lignin sulphonic acid or salt thereof or a glucoside extract of tannins, and a flocculating agent which is an acidulous metal salt having in aqueous solution a pH below 7.0 and which is present in an amount at least sufficient to destroy the colloidal dispersing power of the dispersing agent but insufficient to impair the power of the composite surface-active agent to suspend the selected pigment in stable aqueous suspension as determined by the following test. The least amount of dispersing agent required to produce a smooth stirrable dispersion of an amount of a given pigment using minimum water amounts is determined; this dispersion is diluted to a 10 per cent pigment concentration and there is then added with agitation a solution of the flocculating agent to be tested. When the flocculation point is reached, thickening occurs and a spot test is made on filter paper to ascertain complete flocculation as indicated by a sharp line of demarcation between the flocculated particles and clear liquid. The so determined amount of flocculating agent, or preferably an excess, is then compounded with the dispersing agent to form the composite surface active agent. In an example (6), pellets of channel-type carbon black containing as the composite surface-active agent quebracho powder extract or a naphthalene sulphonic acid-formaldehyde condensate and aluminium chloride in the weight proportions of 400 : 160 (see Group IV (c)) are vigorously stirred into water to form a creamy suspension of carbon which is rendered neutral, e.g. by aqueous sodium carbonate, after addition, if desired, of a plasticizing agent such as rosin or "Bardol" (Registered Trade Mark), which may be previously emulsified by means of sodium oleate, the mixture is intimately mixed with synthetic rubber latex and then treated with a coagulating agent such as brine and sulphuric acid. The black precipitated rubber is filtered, washed and pressed and/or dried. The naphthalene sulphonic acid-formaldehyde condensate may be in the form of the free acid or sodium salt. Examples are given of other metal salts which may replace the aluminium chloride. Specified synthetic rubbers are copolymers of conjugated dienes such as butadiene with one or more unsaturated resin-forming materials, e.g. a GR-S styrene-butadiene latex; other resin-forming materials are vinyl chloride, modified styrenes, acrylonitrile, acrylates and vinyl pyridine. Specification 622,518 is referred to. The Specification as open to inspection under Sect. 91 relates to the production of pigmented rubber utilizing pigments in general, following the above procedure, the composite surface-active agent being defined as comprising any dispersing agent capable of having its dispersing power destroyed by a flocculating agent, and an amount of the flocculating agent to destroy that power. Further examples of flocculating agents include titanium dioxide, various basic or triphenyl methane dyes and soluble primary aromatic amine salts. This subject-matter does not appear in the Specification as accepted.ALSO:A surface-active agent for producing stable aqueous suspensions of organic pigments or carbon black comprises a dispersing agent which is a naphthalene sulphonic acid-formaldehyde condensation product, a lignin sulphonic acid or salt thereof, or a glucoside extract of tannins, and a flocculating agent which is an acidulous metal salt having in aqueous solution a pH below 7.0 and which is present in an amount at least sufficient to destroy the colloidal dispersing power of the dispersing agent but insufficient to impair the power of the composite surface-active agent to suspend the selected pigment in stable aqueous suspension as determined by the test described hereafter. The test consists in first determining for an amount of any given pigment the least amount of dispersing agent required to produce a smooth stirrable dispersion of the pigment using minimum water amounts, then diluting this to 10 per cent pigment content giving a dispersion. There is then added, with agitation, a solution of the flocculating agent to be tested. When the flocculation point is reached, thickening occurs and a spot test is made on filter paper to ascertain complete flocculation as indicated by a sharp demarcation between flocculated particles and the clear liquid. The determined amount of flocculating agent may then be compounded with the dispersing agent to produce the desired surface-active agent. Normally an excess of the flocculating agent is used. The composite agents are able to readily wet and disintegrate aggregates of organic pigments or carbon black in liquids to form suspensions in which the particles are uniformly divided and distributed. They find use in the production of uniformly-pigmented natural and synthetic rubbers (see Groups IV (a) and V), lacquers, paints and enamels (see Group III) and water-in-oil textile printing pastes. Thus, the composite surface-active agent may be compounded with carbon black in the form of beads or pellets which are rapidly disintegrated in water to form a uniform suspension. Pigments mentioned include various forms of the carbon black and benzidine yellows, Hansa yellows, phthalocyanines, indanthrene vat pigment dyes, toluidine reds and lithol reds. In examples: (1) 400 grams of Quebracho extract powder in solid form or in aqueous solution are mixed with 160 grams aluminium chloride forming composite surface-active agents; the disodium salts or the free acid of the dry condensation product of naphthalene sulphonic acid or an aqueous solution of the free acid are combined with aluminium chloride in the same proportions; (2)-(5) aqueous solutions of each of the two composite agents mentioned in (1) are mixed with a powdered channel type carbon black in proportions giving either a suspension containing, e.g. 11 per cent carbon or a paste which is dried in the form of pellets. Examples are given of other metal salts for use in place of aluminium chloride. Specification 622,518 is referred to. The Specification as open to inspection under Sect. 91 relates to a composite surface-active agent comprising any dispersing agent capable of having its colloidal dispersing power destroyed by a flocculating agent, and an amount of the flocculating agent to destroy that power. The flocculating agents specified include titanium dioxide, various basic or triphenyl methane dyes and soluble aromatic primary amine salts. The composite p surface-active agent is said to be capable of dispersing pigments an general and additional examples of pigments are titanium dioxide, clays, whitings, lithopone, blanc fixe, hydrated alumina, calcium carbonate, iron oxides, ochres, ultramarine blue and cadmium reds and yellows. This subject-matter does not appear in the Specification as accepted.ALSO:Paints, lacquers and enamels comprise an organic pigment or carbon black and a composite surface-active agent comprising a dispersing agent which is a naphthalene sulphonic acid-formaldehyde condensation product, a lignin sulphonic acid or salt thereof, or a glucoside extract of tannins, and a flocculating agent which is an acidulous metal salt having in aqueous solution a pH below 7.0 and which is present in an amount at least sufficient to destroy the colloidal dispersing power of the dispersing agent but insufficient to impair the power of the composite surface-active agent to suspend the selected pigment in stable aqueous suspension as determined by the following test. The least amount of dispersing agent required to produce a smooth stirrable dispersion of an amount of a given pigment using minimum water amounts is determined; this dispersion is diluted to a 10 per cent pigment concentration and then is added, with agitation 3, a solution of the flocculating agent to be tested. When the flocculation point is reached, thickening occurs and a spot test is made on filter paper to ascertain complete flocculation as indicated by a sharp line of demarcation between flocculated particles and the clear liquid. The so determined amount of flocculating agent is then compounded with the dispensing agent to form the composite surface-active agent. Thus with reference to carbon black, composite agents comprise 160 grains aluminium chloride and 400 grains of a condensation product of naphthalene sulphonic acid and formaldehyde in the form of the free acid or sodium salt, or of Quebracho extract. Further examples of flocculating agents are aluminium sulphate and acetate, ferric chloride, copper sulphate, zinc chloride, chrome alum, barium chloride, calcium chloride, thorium chloride chromium fluoride and manganese chloride. Organic pigments mentioned for use in oil-in-water emulsion type paints include benzidine yellows, Hansa yellows, phthalocyanines, indanthrene vat pigment dyes, toluidine reds and lithol reds. Specification 622,518, [Group IV(a)], is referred to. The Specification as open to inspection under Sect. 91, defines the composite surface-active agent as one comprising any dispersing agent capable of having its colloidal dispersing power destroyed by a flocculating agent,