| 摘要 |
Disclosed are a composition and method for treating aqueous solutions with N-carboxy alkyl amino alkane polyphosphonic acids which have more than two carbon atoms in their carboxy alkyl group, and their alkali metal salts. The acids and salts are prepared in a good yield by reacting alkali metal salts of amino alkane phosphonic acids in which at least one hydrogen atom of the amino group is unsubstituted, in an alkaline medium with an alpha , beta -unsaturated carboxylic acid at increased temperature. The free acids are preferably recovered from the reaction solution by a treatment with a cation exchange agent. In place of the alpha , beta -unsaturated carboxylic acids there can also be used their anhydrides, esters, or nitriles. The resulting polyphosphonic acids have a good complexing or sequestering effect on polyvalent metal ions.
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