carboxyalkyl groups (containing independently hydroxyl groups, carboxyl substituted ethers, amide substituted ethers or tertiary amides removed from the ether) attached via a carbon or oxygen; these may be Cn H.sub.[(2n+1)-q] Oy Rc q or OCn H.sub.[(2n+1)-q] Oy Rc q ; where n is a positive integer or zero, y is zero or a positive integer less than [(2n+1)-q], q is zero or a positive integer less th