5. alkyl ether carboxylates corresponding to the formula R1???(OCH2CH2)x???OCH2???CO2M wherein R1 is a saturated or unsaturated, branched or unbranched alkyl or alkenyl group of about 8 to about 24 carbon atoms, x is 1 to 10, and M is a water-soluble cation (e.g., sodium laureth carboxylate);