Compositions comprising an ester of an aryloxy-acetic acid, e.g. phenoxyacetic and naphthoxy acetic acids, together with the amine salt of an alkyl substituted aryl sulphonic acid (the alkyl group of which contains at least ten carbons), which acts as a surface active agent, may be used as plasticizers for nitro-cellulose, polyvinyl acetate or polyvinyl chloride (see Group IV (b)).ALSO:Insecticidal compositions comprising an ester of an aryloxy acetic acid and an organic amine salt of an alkyl substituted aryl sulphonic acid, are prepared by reacting an aryloxy acetic acid with an alcohol in the presence of an alkyl substituted aryl sulphonic acid, the alkyl grouping containing at least ten carbon atoms as an esterification catalyst until esterification of said acid with said alcohol is substantially complete, thereafter neutralizing said alkyl substituted aryl sulphonic acid with an organic amine, and thereby forming in situ an amine salt which is available as a surface active agent when the resulting mixture is used. Particular aryloxy acetic acids are those phenoxy and naphthoxy acetic acids which may be nuclearly substituted with lower alkyl or halogen groups, and especially 2:4-dichloro- and 2:4:5-trichloro-phenoxyacetic acids. Alcohols mentioned include n-butanol, isopropanol, glycerol, butoxy ethanol, polypropylene glycol, iso-octyl alcohol and lauryl alcohol. The substituted aryl sulphonic acids are preferably those wherein the alkyl side chain is derived from long chain paraffinic hydrocarbons, and include keryl benzene, keryl toluene and keryl naphthalene sulphonic acids. The term "keryl" denotes a mixture of alkyl side-chains of length ranging from C12 to C16 derived from a highly saturated paraffinic kerosene. Other surface active agents, emulsifiers and aromatic, petroleum or chlorinated aliphatic hydrocarbon oils may also be added to give a stable concentrate, prior to mixing with oil or water for spraying purposes. In examples the esterification mixture of sulphonic acid, phenoxyacetic acid and alcohol are refluxed, removing water azeotropically, excess of the alcohol distilled off, and the ester produced formulated by the addition of a suitable amine (e.g. iso-propylamine, triethylamine, triethanolamine), to neutralize the sulphonic acid and then other additives, emulsifiers and solvents as described.ALSO:Plant growth regulants comprise an ester of an aryloxy acetic acid and an amine salt of an alkyl substituted aryl sulphonic acid (see Group IV (b)). Particular aryloxy acetic acids are 2:4-di and 2:4:5-tri-chlorophenoxy acetic, mono and di-chlorotoloxy acetic and b -naphthoxy acetic acids, esterified with lauryl, n-butyl, iso butyl, iso-octyl alcohols, polypropylene glycol and butoxy ethanol. Particular sulphonic acids are those in which the alkyl substituent contains at least ten carbon atoms, e.g. keryl benzene sulphonic and keryl toluene sulphonic acids (keryl denotes mixture of alkyl chains of from twelve to sixteen carbons). Various amines may be used including isopropylamine, triethylamine and mixtures of high primary aliphatic amines. Formulations may also contain solvents, e.g. petroleum oils such as kerosene, naphtha; aromatic hydrocarbons such as benzene, toluene, methyl naphthalene and chlorinated hydrocarbon oils; or alcohols such as mono-n-butyl ether of ethylene glycols. Other diluents may be present, e.g. emulsifiers such as polyoxy ethylene esters.ALSO:Weed killers or plant growth regulators comprise an ester of an aryloxy acetic acid and an organic amine salt of an alkyl substituted aryl sulphonic acid, (see Group IV(b)). Particular aryloxyacids include 2:4-di and 2:4:5-tri chlorophenoxy-acetic, b -naphthoxy acetic, monoand di-chlorotoloxy acetic acids, esterified with lauryl alcohol, n-butyl, iso-butyl, isooctyl alcohols, polypropylene glycol and butoxy ethanol. The particular sulphonic acids are those in which the alkyl substituent contains at least ten carbon atoms, such as keryl benzene sulphonic, and keryl toluene sulphonic acids (keryl denotes mixture of alkyl chains of from 12 to 16 carbon atoms). Particular amines which are used for salt-formation include isopropylamine, triethylamine, triethanolamine, and mixtures of high primary aliphatic amines. In addition, the formulations may contain as solvents petroleum oils such as kerosene, naphtha, aromatic hydrocarbons, benzene, toluene, methyl naphthalene, and chlorinated hydrocarbon oils; alcohols such as mono-n-butyl ether of ethylene glycol. The solvent hydrocarbon oil is preferably capable of admixture with water, to give a spraying emulsion. Additive surface action agents e.g. polyoxyethylene esters may be added for this purpose if necessary. Other diluents including emulsifiers may be included.