Abstract
The chelate formed between lanthanum and alizarin complexone has been used as the basis of a method for the determination of fluoride in natural waters, with special reference to sea water. The fluoride complex formed with the reagent is developed rapidly at pH 4.50 by the addition of a single buffered reagent and is stable for several days. The fluoride complex is formed in 16% v/v acetone solution; the acetone stabilises the reagent and increases its sensitivity to 0.0018 μg/cm 2. Beer's law is followed up to ca. 25 μg of fluoride. The interference of inorganic ions present in natural waters has been investigated. Abnormally large amounts of aluminium interfere seriously, but can be removed by extraction as its oxinate in a continuous extractor. For sea water of chlorinity within the range 15 to 20% the salt error correction is constant and equal to 4.0%. The method showed a coefficient of variation of 0.3% with a sea water containing 1.37 μg of fluoride/ml.
Published Version
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