The invention comprises as new products derivatives of ethylene imine which contain the following grouping more than once <FORM:0760311/IV(a)/1> wherein x is 0 or 1, R is a hydrogen atom or an alkyl radical, preferably methyl or ethyl, and T is a hydrogen atom or an alkyl group or, in the case where x=1, a carboxylic group or a salt, ester, amide or anilide thereof, and polymers of these derivatives. Among the new derivatives are those having the general formula F.X.(YX)n.F where F represents the above grouping (I), n is 0 to 10 inclusive, x is either (CH2)a, where a is 0 to 8 inclusive or (CH2NR1 CH2)b, where b is 0 to 3 inclusive and R1 is a hydrogen atom or an acyl radical such as stearyl or benzoyl and Y is -CH2NHCOCHR11 (CH2)cCONHCH2-, where c is 0 to 7 inclusive and R11 is either a hydrogen atom or in the case where c=1, an ethylene imine ring attached by the nitrogen atom, and polymers thereof. The preferred compounds are those in which two of the above groupings (I) are linked directly together and those in which there is the above grouping (1) at either end of a molecule separated by a plurality of methylene groups which may be interrupted by imino groups, and polymers thereof. The derivatives in which R and T each represent a hydrogen atom or an alkyl radical may be obtained by condensing a compound of the general formula <FORM:0760311/IV(a)/2> wherein Alkyl is an alkyl radical containing no more than four carbon atoms with a compound containing two or more primary aliphatic amino groups. The condensation is preferably effected in the presence of a basic catalyst, e.g. sodium methoxide or ethoxide. Suitable amino compounds include propylene diamine, triethylene tetramine, hexamethylene diamine, and lower molecular weight polyamides having terminal primary amino groups and containing up to twenty -CONH- linkages. Derivatives in which x is 1, R is a hydrogen atom or an alkyl radical, and T is a carboxylic ester group may be obtained by condensing an ester of the general formula: <FORM:0760311/IV(a)/3> wherein the alkyl radical is one containing no more than 4 carbon atoms with a compound containing two or more primary aliphatic amino groups. The condensation is preferably carried out in the presence of a basic catalyst and the molecular ratio of the ester to the amino compound may vary from 2 : 1 to 1 : 1. The products may be subjected to alkaline hydrolysis to convert each ester group to a carboxylic group or salt thereof. Compounds in which T is the amide or anilide of a carboxylic group and x is 1 may be obtained by reacting, preferably in the presence of a basic catalyst, a compound containing two or more primary aliphatic amino groups with a compound of the general formula (II) above, wherein one of the ester groups attached to the C atom adjacent to the N atom is replaced by an amide or anilide group. The products may be reacted with organic compounds containing such active groups as -NH2, -COOH, -SH, or phenolic OH groups or containing such inorganic ions as halide, cyanate, bisulphite or thiosulphate ions. If such groups or ions are present in compounds of high molecular weight, e.g. of not less than 10,000 e.g. textile fabrics (see Group IV (c)), the physical and chemical properties of such compounds may be modified by reacting with small amounts, e.g. between 1/2 per cent and 20 per cent by weight of the new products. The ethyleneimine derivatives may also be applied to linear molecules of high molecular weight, e.g. of not less than 10,000 which do not contain an active group or ion, e.g. cellulosic or synthetic linear super polyamide fibres (see Groups IV (c) and VIII). If the high molecular weight compound is water-soluble addition of the ethyleneimine derivatives to an aqueous solution thereof results in ultimate insolubilization of the compound. Thus, if an aqueous solution of polymethacrylic acid containing a small amount of the derivative is applied to a surface and the water evaporated off, the resultant film is water resistant. Also a solution of polyethyleneimine is transformed from a viscous liquid to a rigid gel on treatment with one of the derivatives and on drying the gel and grinding a powder having good anion exchange properties is obtained. To stabilize the ethyleneimine derivatives or their solutions free alkali must be present and to cause polymerization addition of acid or acid-yielding material is required in order to give the reactive ethylene immonium ion. In examples: (1) ethylene imine is added to methyl acrylate dissolved in methanol and the methyl ester of N : N-ethylene-alanine which is formed is added to ethylene diamine in methanol, a small amount of alkaline catalyst also being present. After standing for 48 hours the methanol is removed and the residue is dissolved in boiling 2-butanone and cooled to yield crystals of a product having the formula: <FORM:0760311/IV(a)/4> which polymerizes to a gel in aqueous solution and when added to aqueous solutions of polyethyleneimines causes irreversible gelation; (2) the addition product of ethylene imine and diethyl maleate is purified by reduced pressure distillation to yield the diethyl ester of ethylene imino-succinic acid which is then condensed with diethylene triamine (molar ratio 2 : 3), using sodium ethoxide as catalyst. The viscous liquid product obtained dissolves readily in water and if the acid is added to a 15 per cent solution of the product irreversible gelation occurs on standing or warming. The product of (2) may be dissolved in methanol and stearyl chloride added at 15 DEG C. with vigorous stirring whilst maintaining the pH at about 11 by the addition of sodium hydroxide to yield a product suitable for the treatment of cotton fabric (see Group IV (c)); (3) methyl crotonate and ethyleneimine are reacted together to form the methyl ester of b -ethyleneimino-butyric acid which is then treated with triethylene tetramine in the presence of a solution of sodium methoxide in methanol to yield a product having the formula: <FORM:0760311/IV(a)/5> (4) the product obtained by reacting ethylene imine and methyl crotonate as in (3) is treated with hexamethylene diamine in the presence of sodium methoxide in methanol to yield a crystalline product analogous in appearance and properties to the product of (1); (5) an aqueous solution containing polyethyleneimine and a small amount of the product of (1) is heated to 80 DEG C. in the presence of hydrochloric acid and the rigid gel formed is dried and ground to yield a product having high affinity for anions in aqueous solution. The first Provisional Specification includes ethyleneimine derivatives containing the following grouping more than once: <FORM:0760311/IV(a)/6> wherein X1, Y1, X2 and Y2 each represent a hydrogen atom or an alkyl or aralkyl radical and R1 and R2 each represent a hydrogen atom or an alkyl radical. These may be obtained by reacting ethyleneimine or the appropriately substituted ethyleneimine with a compound containing the grouping (R1)(R2)C=CH-C(O)-more than once, e.g. glycol di-acrylate, pentaerythritol tetra acrylate, or 1,6-hexamethylene di-acrylamide; and an example is given in which ethyleneimine is reacted with ethylene glycol di-acrylate in methanol to yield a liquid product, soluble in water.ALSO:The invention comprises as new products derivatives of ethylene imine which contain the following grouping more than once (I) <FORM:0760311/IV(b)/1> wherein x is 0 or 1, R is a hydrogen atom or an alkyl radical, preferably methyl or ethyl, and T is a hydrogen atom or an alkyl group or, in the case where x=1, a carboxylic group or a salt, ester, amide or anilide thereof, and polymers of these derivatives. Among the new derivatives are those having the general formula :-F.X.(YX)n.F, where F represents the above grouping (I), n is 0 to 10 inclusive, x is either (CH2)a, where a is 0 to 8 inclusive or (CH2NR1 CH2)b, where b is 0 to 3 inclusive and R1 is a hydrogen atom or an acyl radical such as stearyl or benzoyl and Y is -CH2NHCOCHR11 (CH2)cCONHCH2-, where c is 0 to 7 inclusive and R11 is either a hydrogen atom or in the case where c=1, an ethylene imine ring attached by the nitrogen atom, and polymers thereof. The preferred compounds are those in which two of the above groupings (I) are linked directly together and those in which there is the above grouping (I) at either end of a molecule separated by a plurality of methylene groups which may be interrupted by imino groups, and polymers thereof. The derivatives in which R and T each represent a hydrogen atom or an alkyl radical may be obtained by condensing a compound of the general formula <FORM:0760311/IV(b)/2> wherein Alkyl is an alkyl radical containing no more than four carbon atoms with a compound containing two or more primary aliphatic amino groups. The condensation is preferably effected in the presence of a basic catalyst, e.g. sodium methoxide or ethoxide. Suitable amino compounds include propylene diamine, triethylene tetramine, hexamethylene diamine, and lower molecular weight polyamides having terminal primary amino groups and containing up to twenty -CONH- linkages. Derivatives in which x is 1, R is a hydrogen atom or an alkyl radical, and T is a carboxylic ester group, may be obtained by condensing an ester of the general formula (II) <FORM:0760311/IV(b)/3> the alkyl radical not containing more than 4 carbon atoms with a compound containing two or more primary aliphatic amino groups. The condensation is preferably carried out in the presence of a basic catalyst and the molecular ratio of the ester to the amino compound may vary from 2:1 to 1:1. The products may be subjected to alkaline hydrolysis to convert each ester group to a carboxylic salt thereof. Compounds in which T is the amide or anilide of a carboxylic group and x is 1 may be obtained by reacting, preferably in the presence of a b