Conductivity and Dissociation Equilibrium of Extremely Anhydrous Hydrogen Fluoride

Abstract

We have studied the conductivity of extremely anhydrous hydrogen fluoride (AHF) and obtained a minimum conductivity of 0.7 • 10 -6 S cm -1 at 0~ We have recognized that water in AHF at concentrations below 1 • 10 -3 tool dm -3 shows an ideal dissociation and that the limiting equivalent conductance of AHF is 436 S cm 2 mol-1 at 0~ The ideal relationship between the conductivity and water concentration obtained in this work was extrapolated to the ultra-micro water concentration region. The conductivity of 0.7 x 10 -6 S cm -1 corresponds to a water concentration of 1.85 • 10 -6 tool dm -3 (0.033 ppm) in the above relationship; however, this conductivity is not due to the dissociation of water but to that of hydrogen fluoride. We recognized that the relationship between the conductivity and water concentration of AHF coincides completely with that of ultra-pure water in the ultra-micro conductivity region (10 -8 S cm-1).) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.129.120.3 Downloaded on 2015-06-04 to IP

Vapor‐Liquid Equilibrium of the Binary System HF ‐ H 2 O Extending to Extremely Anhydrous Hydrogen Fluoride

“…In the range of water concentrations over 1 • 10 -2 mol dm -3 (180 ppm), the water concentrations were measured using the Karl Fischer method. The calibration curve was obtained from both results (4,5). For the vapor-liquid equilibria, measured water contents less than 1 mol dm -3 (18,000 ppm) by the conductivity method using the calibration curve and greater than 1 mol dm -3 (18,000 ppm) using a neutralization titration method.…”

“…Frendenhagen et al studied conductivities over the range from 0.013 to 0.5N water in hydrogen fluoride and obtained a conductivity of 1.4 x 1O -5 S cm -1 for anhydrous hydrogen fluoride at 15~ (1-4). Kilpatrick et al improved the methods for the purification of anhydrous hydrogen fluoride, which yielded acid with much lower conductivity, 1.6 • 10 -6 S cm ~1 at 0~ than reported previously (5)(6)(7).…”

“…It is important for promoting a technology of dehydration of HF that the equilibrium of the binary system HF-H20 is determined in the range of trace amounts of water. Here we have determined the binary system equilibrium, especially in the range of low water concentrations, using the conductivity method developed by ourselves (4,5). We have calculated the activity coefficient of HF and H20 at the boiling point for the entire binary system HF-H20.…”

Measurement Of Adsorbed Moisture Concentration On Various Kinds Of Solid Surfaces By Using Anhydrous Hydrogen Fluoride

“…The variation in the electric conductivity of liquefied AHF at the outlet of sample tube was then measured with the conductivity cells. Total amount of moisture in liquefied AHF is easily derived from the relationship of electric conductivity to moisture level [7]. …”