回転ベリリウム電極によるフッ素の電量滴定

概要

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A new coulometric titration method for determining fluoride was developed. Aluminum ion is coulometrically dissoluted from a pure aluminum metal electrode to form the complex with fluoride ion in 0.5M deoxygenated acetic acid solution, and the end point is potentiometrically detected using a rotational beryllium electrode at 600rpm. The standard deviation of this mothod was 2.3% for 2mg of fluorine, and the lower limit of detection by this method was 4ppm. The anodic dissolution current was ordinarily 40.20mA. Polarization characteristics of the rotating beryllium electrode were investigated in absence or existence of fluoride. The equilibrium potential was ca. -0.5V (vs. SCE) in the 0.5M acetic acid solution, and it changed to ca. -1.1V after an addition of fluoride. The polarization curves of the electrode showed characteristic hysteresis even in the existence of fluoride at the anodic side of polarization. Amperometric end point determination was endeavored by the beryllium electrode, but the method was not superior to the potentiometric method.
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