Abstract
The relations between the concentration of trace water in anhydrous hydrofluoric acid (AHF) and its conductivity were investigated by the additional method in closed system. The conductivity was measured by the conductivity cells with the smooth platinum electrodes (cell constants from 0.3 to 3 cm-1)at fixed frequency from 1000 to 3000 Hz. The correction for polarization error at frequency over 1000 Hz was negligible small. The effect of temperature on conductivity was : k=kt(1 +0.0098t) where k : conductivity at 0°C, kt : conductivity at ±t°C. The variation of conductivity was examined when the known amount of water or other impurities were added to high purity AHF. The relations between the conductivity (k, Ω -1 cm -1) and the concentration of water (C, ppm) less than 100 ppm, at which concentration Karl Fischer method was inapplicable, were
C, (110) ppm : log C=1.00 log k + 4.62
C, (10100) ppm : log C= 1.06 log k + 4.84
The conductivity was not affected by the presence of HSO3F, H2SiF6 and SO2 at the concentration of each several hundred ppm. The flow cells of by-pass type and on-stream type were developed by directly connecting with storage tank and pipe line. The use of the smooth platinum electrodes was necessary for stability and life of those cells. By using this new technique, the continuous measurements of the trace water at ppm level in AHF which has low conductivity at 10 -5 Ω -1cm -1level have been made possible.
