The Potentiometric Determination of Fluoride with Lanthanum Nitrate and Its Application to the Micro-Determination of Fluorine in Organic Compounds

摘要

The unbuffered fluoride solution is adjusted to pH 6.3 and titrated with 0.05N lanthanum nitrate solution. A rapid decrease in pH at the end-point, due to hydrolysis of the excess of lanthanum ions, is followed with a quinhydrone indicator/calomel reference electrode system. Sulphate, phosphate, carbonate and silicate ions interfere. Methods for removal of all but the first of these are described. The method has been applied to the determination of fluorine in organic compounds. Results were within 0.5% absolute. (Author)