KINETOCHROMIC SPECTROPHOTOMETRY .I. DETERMINATION OF FLUORIDE BY CATALYSIS OF ZIRCONIUM-XYLENOL ORANGE REACTION

The reaction between slightly aged solutions of zirconyl chloride and Xylenol Orange is catalysed by the presence of substoi-chiometric amounts of fluoride, phosphate, arsenate, sulphate, citrate or oxalate. The reaction provides a method for determining fluoride in amounts from 0·5 to 5 μg in a final volume of 100 ml. This kineto-chromic reaction provides an effective molar absorptivity of 2·0 × 105 for the fluoride ion. The colour reaches maximal development within 90 min and remains stable thereafter for 60 min, when measured against a reaction system blank containing no fluoride. Because of its substoichiometric nature the reaction may not be used for the determination of large amounts of fluoride. © 1969.