| 摘要 |
Minute quantities of fluoride in water are determined using a reagent comprising the alizarin complexan (3 aminoethyl alizarin N,N, diacetic acid), chelate of lanthanum, cerium III, or praeseodymium in an aqueous solution buffered with sodium acetate-acetic acid, and including an alcohol. In an example, solution A is prepared by adding alizarin complexan dye to distilled water, adding sodium hydroxide solution to dissolve the dye, followed by sodium acetate, glacial acetic acid and anhydrous isopropanol. Solution B is prepared by adding lanthanum nitrate to distilled water, followed by sodium acetate, glacial acetic acid and anhydrous isopropanol, to which is added a paste of polyvinyl pyrrolidone, solutions A and B then being mixed. A polymeric plasticizer other than polyvinyl pyrrolidone may be included in the reagent. The fluoride content of water may be determined colorimetrically in the range 600-675 mm using the above reagent. Details of interfering materials are disclosed together with the stability of the reagent. |
