wis any anhydride groups remaining in the water insoluble cross linked polycarboxylic or polyhydroxy polycarboxylic acid are hydrolyzed by alkaline hydrolysis in the water insoluble cross linked polycarboxylic or polyhydroxy polycarboxylic acid composition the ratio of the initially charged diamino hydroxy alkane to the initially charged poly alkylene maleic anhydride is suitably between about 1 u00d7 10 5 to 1 u00d7 10 3 moles of cross linker to 1 0 gram of polymer charged there is thus formed compound v namely str8 wherein most suitably m 0 or 1 p 3 6 and w 6 and x and y may lie between 7 and 10 000 the method of making the water insoluble cross linked polycarboxylic acid composition entails cross linking a polymer of formula i with an alpha omega diamino alkane of formula ii under strictly anhydrous conditions and hydrolyzing the unreacted anhydride groups a volume of alkylene cross linked poly alkylene maleic anhydride conforming to formula i is added to a reaction vessel a volume of alpha omega diamino alkane con forming to formula ii is also added to the reaction vessel the ratio of the initially charged diamino alkane to the initially charged poly alkylene maleic anhydride is suitably between about 1 u00d7 10 5 to 1 u00d7 10 3 moles of cross linker to 1 0 grams of polymer this is performed typically by suspending the polymer of formula i in an anhydrous solvent suitably acetone and adding a solution of an alpha omega diamino or diaminohydroxy alkane in a similar solvent such as acetone for 1 5 hours followed by stirring for 24 48 hours during which the reaction mixture is allowed to stand at room.