Kinetochromic spectrophotometry-I Determination of fluoride by catalysis of the 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 mug in a final volume of 100 ml. This kineto-chromic reaction provides an effective molar absorptivity of 2.0 x 10(5) 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.
Cabello-Tomas
M L
ML
Chemistry Department, Imperial College, London, S.W.7. UK.
West
T S
TS