Ester mixtures having surface active properties are obtained by reacting a triglyceride fat or fatty oil with a polyethylene glycol of the formula HO CH2-(CH2O.CH2)n-CH2OH where n is an integer from 2 to 12 in the ratio of substantially 2 moles of triglyceride per mol of polyethylene glycol at an elevated temperature and in the presence of an esterification catalyst under such conditions as to effect limited inter-esterification of the reactants while avoiding the complete de-esterification of the triglyceride and the formation of glycerol.  The product comprises a mixture of unreacted triglycerides, mono- and di-glycerides, and mono- and di-esters of the polyethylene glycol.  Suitable esterification catalysts are lime, soda, and phosphoric acid and the reaction is preferably carried out in an inert atmosphere at from 205 DEG  to 225 DEG  C. under atmospheric pressure for about 2 hours. Specified triglycerides are hydrogenated and non-hydrogenated drying, semi-drying or non-drying oils and fats, e.g., linseed oil, ground nut oil, apricot kernel oil, almond oil, olive oil, palm oil, neat's foot oil, hydrogenated whale oil, tallow and lard.  Examples are given in which polyethylene glycol 300 is reacted with linseed oil, ground nut oil, apricot kernel oil, olive oil and hydrogenated palm oil.  The products may be used as constituents of foundry cores (see Group XXII), paints, varnishes and lubricants (see Group III), textile sizing agents (see Group V), insecticidal, cosmetic, and pharmaceutical compositions, and foodstuffs (see Group VI) and for coating paper (see Group VIII) or cotton wool.ALSO:A paint, varnish, lubricating composition, or emulsion contains a proportion of an ester mixture having surface active properties, said mixture being obtained by reacting a triglyceride fat or fatty oil with a polyethylene glycol of the formula: - HO.CH2-(CH2-O-CH2)n-CH2OH, wherein n is an integer from 2 to 12, in the ratio of substantially 2 mols of triglyceride per mol of polyethylene glycol to effect limited inter-esterification of the reactants without formation of glycerol (see Group IV(b)).  The ester mixture is also completely miscible with hydrocarbons such as kerosene, paraffin and heavier petroleum fractions and with natural and synthetic fatty acid triglycerides and these mixtures as such or in solution in organic liquids can be formed into fine emulsions with water.  In examples: (1) a paint is obtained by diluting with an organic solvent or with water a white ground pigment prepared from a mixture of natural linseed oil and linseed oil treated with polyethylene glycol 300 as above; (2) a varnish is prepared from ordinary linseed oil and linseed oil treated with polyethylene glycol 300 as in (1); (3) a glycero-phthalic paint is obtained by adding linseed oil treated as in (1) to a paint based on a solution of a glycerophthalic resin in a solvent such as kerosene; (4) ground nut oil treated with polyethylene glycol 300 as above is incorporated in cutting oils to render the oil readily emulsifiable.ALSO:A textile sizing agent contains a proportion of an ester mixture having surface active properties said mixture being obtained by reacting a triglyceride fat or fatty oil with a polyethylene glycol of the formula: HO.CH2-(CH2-O-CH2)n-CH2OH wherein n is an integer from 2 to 12 in the ratio of substantially 2 mols of triglyceride per mol of polyethylene glycol to effect limited esterification of the reactants without formation of glycerol (see Group IV(b)).  A suitable ester mixture is obtained by treating ground-nut oil with polyethylene glycol 300 as above.ALSO:An insecticidal, pharmaceutical or cosmetic composition or a foodstuff contains a proportion of an ester mixture having surface active properties obtained by reacting a triglyceride fat or fatty oil with a polyethylene glycol of the formula HO.CH2-(CH2OCH2)n-CH2OH where n is an integer from 2 to 12 in the ratio of substantially 2 mols of triglyceride per mol of polyethylene glycol at an elevated temperature and in the presence of an esterific catalyst under such conditions as to effect limited inter-esterification of the reactant while avoiding the complete de-esterification of the triglyceride and the formation of glycerol (see Group IV(b)). Specified compositions are: (1) a water-dispersible derris extract comprising a chloroform extract of Derris Elliptica, acetone, chloroform, ground nut oil treated with polyethylene glycol 300 as above, an emulsifying agent and water; (2) a water-dispersible pyrethrum extract comprising pyrethrum extract, ground nut oil treated as in (1), an emulsifying agent and water, (3) a nasal oil comprising eucalyptol, apricot kernel oil treated with polyethylene glycol 300 as in (1), and olive oil; (4) a vitaminised oil comprising shark liver oil, cod liver oil and apricot kernel oil oil treated as in (3); (5) a water-dispersible olive oil comprising pure olive oil and olive oil treated with polyethylene glycol 300 as in (1); (6) a cosmetic lotion comprising hydrogenated palm oil treated with polyethylene glycol as in (1), polyethylene glycol 300 stearate, petroleum jelly, water, fungicide and perfume; (7) an excipient comprising hydrogenated palm oil treated as in (6) and untreated hydrogenated palm oil of melting point 38-40 DEG C., the excipient obtained in (7) may also be incorporated with antibiotics to preserve the latter; and (8) an excipient for suppositories comprising hydrogenated palm oil treated as in (6) and untreated hydrogenated palm oil of m.p. about 36 DEG C.  A solution of ground nut oil treated as in (1) may also be mixed with the facts or oils normally employed in the manufacture of cakes, bread, sponge fingers, biscuits and rusks.