The components of a mixture of acidic or neutral non-hydrocarbon organic materials, of which at least one is acidic, are separated from a liquid hydrocarbon in which they are dissolved by intimately contacting the solution with an anion-exchange resin impregnated with an auxiliary liquid which is water, an organic liquid, a mixture of organic liquids or a mixture of an organic liquid and water which is immiscible with the hydrocarbon or sufficiently strongly adsorbed by the resin not to be removed by the hydrocarbon and is chemically stable under the conditions of use (forming salts or tautomerizing under the conditions of use does not exclude); separating the hydrocarbon liquid freed of non-hydrocarbon materials from the resin, eluting the resin with an auxiliary liquid to obtain a solution of the physically adsorbed non-hydrocarbon material and then recovering a solution of an acidic component of the mixture by washing the resin with a solution capable of regenerating it. The process may be used for purifying hydrocarbons such as gasolines, kerosenes, diesel fuels, gas oils, aviation turbine fuels, jet fuels, naphthas, lubricating oils and coal-tar and synthetic benzene, toluene, xylene, hexane, heptane octane and their homologues. The acidic component of the mixture may be naphthenic acids, sulphonic acids, phenols, thiophenols, naphthasulphonic acids, fatty acids or oil oxidation acids which may be mixed with similar or other acidic material or neutral compounds such as ketones, quinones, sulphones, sulphoxides, mercaptans, phenothiazines, porphyrins, carbazoles or indoles. The auxiliary liquid may contain water, alkanols containing up to 5 carbon atoms, alkanolamines, nitroparaffins, nitrates such as diethylene glycol mononitrate, diols or triols; other compounds such as ketones, esters, cyclohexanol, cyclic and aliphatic ethers, chloroform, amines and heterocyclics such as pyridine and dioxan are unsuitable on their own but may be mixed with one another to give suitable auxiliary liquids or may be mixed with other auxiliary liquids to enhance their properties, such auxiliary liquids may be used for resin elution or resin pretreatment. The resin used may be an aminated copolymer of a monovinyl and divinyl aromatic compound, an amine-aldehyde resin or those resins described in Specifications 679,850, 679,851, 679,852, 471,366 and 730,757, [all in Group IV (a)], and is generally used in the hydroxide form. The resin may be regenerated by elution with an aqueous alcoholic alkali solution and the chemically adsorbed acidic material recovered from the solution by acidification. In Example (4) a gas oil containing 83 p.p.m. non-basic nitrogen, mainly substituted carbazoles, and having an acid value of 0.12 mg. KOH is purified using a methanol pretreated "Amberlite" (Registered Trade Mark) 400 (OH) resin and eluting first with methanol and then with aqueous methanolic NaOH to recover the adsorbed impurities. Specification 820,271 also is referred to.ALSO:The components of a mixture of acidic or neutral non-hydrocarbon organic compounds which are soluble in a liquid hydrocarbon and of which at least one is acidic are separated by intimately contacting a solution of the mixture in the liquid hydrocarbon with an anion exchange resin impregnated with an auxiliary liquid, which may be water, an organic liquid or mixture of liquids or a mixture of an organic liquid with water which is either immiscible with the hydrocarbon or is sufficiently strongly adsorbed by the resin not to be removed from it by the hydrocarbon and which is chemically stable but may form salts or tautomerize under the reaction conditions; separating the liquid hydrocarbon freed of non-hydrocarbon materials from the resin, eluting the resin with an auxiliary liquid to obtain a solution of the physically adsorbed component of the mixture and then recovering a solution of an acidic component of the mixture by washing the resin with a solution capable of regenerating it. The method may be used to purify the liquid hydrocarbon. The acidic component of the mixture may be naphthenic acids, sulphonic acids, phenols such as alkyl phenols, naphthasulphonic acids, thiophenols such as alkyl tihophenols, fatty acids or oil oxidation acids. They may be mixed with similar or other acidic materials or neutral non-hydrocarbon materials, for example, non-basic nitrogen compounds such as phenothiazines, carbazoles, indoles and porphyrins, ketones, quinones, sulphoxides, sulphones and mercaptans. Such mixtures may occur in petroleum oils or distillates or in coal tar or synthetic benzene, toluene, xylenes, hexane, heptane, octane and their homologues and such hydrocarbons may be purified and the non-hydrocarbon recovered. The auxiliary liquid may be water, an alkanol containing less than 5 carbon atoms, an amino alkanol such as ethanolamine, a nitroparaffin such as nitromethane, a nitrate such as the monomethyl ether of diethylene glycol mononitrate or diols or triols such as glycol and glycerol. Other compounds such as ketones, esters, cyclohexanol, cyclic and aliphatic ethers, chloroform, amines and heterocyclics such as pyridine are unsuitable on their own but may be mixed with one another to give suitable auxiliary liquids or with other auxiliary liquids to enhance their properties, such mixtures may be used for resin pretreatment or resin elution. Typical mixtures include dioxan and pyridine, 30% monoethanolamine and 70% methyl ethyl ketone, 30% monoethanolamine and 70% 1,2-dimethoxyethane, 30% monoethanolamine and 70% dioxan, 50% triethanolamine and 50% methyl ethyl ketone, 15% monoethanolamine, 15% ethylene glycol and 70% methyl ethyl ketone (all percentages by volume). The resin used may be an aminated copolymer of a mono-vinyl and di-vinyl aromatic compound, e.g. styrene and di-vinyl benzene or amine-aldehyde resins or those resins described in Specifications 679,850, 679,851, 679,852, 714,366 and 730,757, [all in Group IV (a)]. The resin is generally used in the form of its hydroxide and the resin known as "Amberlite IRA 400" is preferred ("Amberlite" is a Registered Trade Mark). Elution with an auxiliary liquid gives a solution of the physically adsorbed material and a further elution with an aqueous alcoholic alkali, e.g. N.KOH in methanol containing 10% water will give a solution of the chemically adsorbed material which may be recovered by neutralization and distillation and will regenerate the resin for further use. In the examples: (1) benzene containing C-9C13 alkyl phenols and naphthenic acids is passed over a water-treated "Amberlite" resin, the alkyl phenol recovered by eluting with pyridine in dioxane and the naphthenic acids recovered using aqueous alcoholic KOH; (2) a similar run is described using an aqueous nitromethane-treated resin; (3) a monoethanolamine-dioxane-treated resin is treated with a carbazole-alkyl phenol in benzene solution, the carbazole recovered by eluting with methanolic benzene and the phenol using aqueous methanolic NaOH; (4) a gas oil containing 83 p.p.m. non-basic nitrogen and having acid value of 0.12 mg. KOH per gram is purified using a methanol treated resin, the non-basic nitrogen compounds are recovered by methanol elution and the acids using aqueous methanolic NaOH. Specification 820,271 also is referred to.