straight-chain or branched alkyl of 1 to 4 carbon atoms; X.sup.1, X.sup.2, X.sup.3 individually are a carboxylate --(COO.sup.--) and/or sulfonate-(SO.sub.3 -) , n.sub.1, n.sub.2, n.sub.3 are the same or different whole numbers from 0 to 5, M is an alkali