Threads having a smooth, satiny appearance, without high lustre, are obtained when cellulose acetate is extruded from tiny apertures into a bath containing suspended in an organic solvent a starch derivative obtainable by reacting starch in an alkaline medium with a substituted cyclic dicarboxylic anhydride of formula- <FORM:0717901/IV (a)/1> wherein R is a dimethylene or trimethylene radicle and R1 is an alkyl, alkoxy, alkenyl, aralkyl, aralkenyl, acyloxy or aracyloxy group, or the corresponding acid chloride, and thereby producing a starch mono-ester of the substituted anhydride, or salt thereof, which is reacted, in the presence of water, with a compound containing a polyvalent metallic ion to produce the salt of the mono-ester. R1 may contain 1-18 C atoms and may be joined to R via a carbon-to-carbon bond, through two carbon-to-carbon bonds or via an ester or ether linkage. Representative of specified anhydrides are a -benzyl-or-styryl-succinic-, cyclohexane 1, 2-dicarboxylic acid-, octyloxy succinic-, decenyl-succinic-and heptyl glutaric anhydrides. Corn, potato, tapioca, sago, rice, wheat, waxy maize, sweet potato and arrow-root starches are specified. Polyvalent metal salts specified are water-soluble salts of Cu, Hg, Al, Zr, Fe, Cr, Sn, Ba, Ca and Sr. Specification 691,364 is referred to.ALSO:The invention comprises free-flowing starch derivatives obtainable by reacting starch in an alkaline medium with a substituted cyclic dicarboxylic anhydride of formula <FORM:0717901/IV (b)/1> wherein R is a dimethylene or trimethylene radicle and R1 is an alkyl, alkoxy, alkenyl, aralkyl, aralkenyl, acyloxy or aracyloxy group, or the corresponding acid chloride, and thereby producing a starch mono-ester of the substituted anhydride or salt thereof which is reacted, in the presence of water, with a compound containing a polyvalent metallic ion to produce the salt of the mono-ester. The product shows great increase in ease of flow in the dry state, resistance to wetting by water and is susceptible to wetting by organic solvents. After the first stage the mono-ester may be obtained as an acid or a salt depending on the pH of the reaction mixture which may vary during reaction. R1 may contain 1-18 C atoms and may be joined to R via a carbon-to-carbon bond, e.g. in alkenyl-, alphabenzyl- or alpha-styryl-succinic anhydrides, through two carbon-to-carbon bonds as in the adduct of maleic anhydride with methyl pentadiene or cyclohexane 1,2-dicarboxylic acid anhydride, or via an ether or ester linkage as in actyloxy-, capryloxy- or alpha-phenonacetoxy-succinic anhydrides. Corn, potato, tapioca, sago, rice, wheat, waxy maize, sweet potato and arrowroot starches are specified. The starch should be ungelatinized. The anhydride may be added at room temperature to an aqueous suspension of the starch at a pH of preferably 7-11; commercially dry starch may be blended with a dry alkaline material, e.g. trisodium phosphate or sodium carbonate, and with the anhydride and then heated, or the starch may be suspended in an organic liquid, e.g. benzol, and the anhydride added together with sufficient pyridine to neutralize the reagent. 0.1-100 per cent of anhydride may be used based on dry starch. Polyvalent metal salts specified are water-soluble salts of Cu, Hg, Al, Zr, Fe, Cr, Sn, Ba, Ca and Sr. Preferably an excess of polyvalent metal salt is used although quantities of 0.1-10 per cent based on dry starch are also specified. The product may be distributed in the dry state as a blend of mono-ester with the polyvalent metal compound and reaction subsequently effected on addition of water. A water solution of the polyvalent metal compound may be sprayed into the agitated dry mono-ester. In examples (1) corn starch is treated with decenyl succinic anhydride in aqueous sodium carbonate and the product isolated at pH 7.0 and treated in aqueous suspension with aluminium sulphate; (2) tapioca starch is treated with heptyl glutaric acid in aqueous sodium carbonate and the product isolated at pH 7.0 is treated in aqueous suspension with ferrous or ferric sulphates; (3) rice starch in aqueous sodium hydroxide is treated with iso-butylene succinic anhydride and the product isolated at pH 7.0 is treated in aqueous suspension with aluminium sulphate; (4) an acid-converted, thin-boiling corn starch (60 fluidity) is treated with triisobutenyl succinic anhydride in aqueous sodium carbonate and the neutralized product isolated and treated in aqueous suspension with stannic chloride; (5) the first stage product of (4) is treated in aqueous suspension with calcium formate, barium chloride or strontium nitrate; (6) potato starch, in aqueous sodium carbonate, is treated with octadecenyl succinic acid chloride and the neutralized product isolated and treated in aqueous suspension with copper sulphate; (7) air-dry waxy maize starch is blended with sodium carbonate and sprayed with a toluene solution of octenyl succinic anhydride, heated at 90-100 DEG F. and the toluene freed product treated in aqueous suspension at pH 6.5 with ceric sulphate; (8) wheat starch is treated with capryloxy succinic anhydride in aqueous sodium hydroxide and the isolated product treated in aqueous suspension with chromic chloride; (9) corn starch is treated with octenyl succinic anhydride in aqueous sodium carbonate and the isolated product treated in aqueous suspension with aluminium sulphate; (10) potato starch, suspended in benzyl, is treated with nonenyl succinic anhydride and pyridine and the product treated in aqueous suspension with zinc chloride; and (11) corn starch is treated with methylene succinic anhydride in aqueous sodium hydroxide and the product treated in aqueous suspension with aluminium sulphate. Specification 691,364 is referred to.ALSO:Free flowing starch derivatives obtainable by reacting starch in an alkaline medium with a substituted cyclic dicarboxylic anhydride of formula <FORM:0717901/V/1> where R is a dimethylene or trimethylene radicle and R1 is an alkyl, alkoxy, alkenyl, aralkyl, aralkenyl, aryloxy or aracyloxy group, or the corresponding acid chloride, and thereby producing a starch monoester of the substituted anhydride, or salt thereof, which is reacted, in the pressure of water, with a compound containing a polyvalent metallic ion to produce the corresponding salt of the monoester, are used as water-resistant textile sizes and finishes and rubber products are given a smooth satiny finish when dipped in a solution of the esters in naphtha. R1 may contain 1-18 C atoms and may be joined to R via a carbon-to-carbon bond, through two carbon-to-carbon bonds or via an ether or ester linkage. Representative of specified anhydrides are a -benzyl- or-styryl-succinic-, cyclohexane 1, 2 dicarboxylic acid-, octyloxy-succinic-, decenylsuccinic- and heptyl glutaric anhydrides. Corn, potato, tapioca, sago, rice, wheat, waxy maize, sweet potato and arrowroot starches are specified. The starch should be ungelatinized. Polyvalent metal salts specified are water-soluble salts of Cu, Hg, Al, Zr, Fe, Cr, Sn, Ba, Ca and Sr. Specification 691,364, [Group IV (a)], is referred to.ALSO:Free flowing starch derivatives obtainable by reacting starch in an alkaline medium with a substituted cyclic dicarboxylic anhydride of formula: <FORM:0717901/VI/1> where R is a dimethylene or trimethylene radicle and R1 is an alkyl, alkoxy, alkenyl, aralkyl, aralkenyl, aryloxy or aracyloxy group, or the corresponding acid chloride, and thereby producing a starch monoester of the substituted anhydride, or salt thereof, which is reacted, in the presence of water, with a compound containing a polyvalent metal ion to produce the corresponding salt of the monoester, are used as carriers for insecticidal powders or when derived from metals such as mercury, may themselves have insecticidal or rodenticidal properties; R1 may contain 1-18 C atoms and may be joined to R via a carbon-to-carbon bond, through two carbon-to-carbon bonds, or via an ether or ester linkage. Representative of specified anhydrides are a -benzyl-or -styryl-ricinic-, cyclo-hexane 1, 2-dicarboxylic acid-, octyloxy-ricinic-, decenylricinic- and heptyl glutaric anhydrides. Corn, potato, tapioca, sago, rice, wheat, waxy maize, sweet potato and arrowroot starches are specified. The starches should be ungelatinized. Polyvalent metal salts specified are water soluble salts of Cu, Hg, Al, Zr, Fe, Cr, Sn, Ba, Ca and St. Specification 691,364, [Group IV(b)], is referred to.