Development of hydrogen ion selective electrode with lithium phosphate glasses for the use in solutions containing hydrofluoric acid.

概要

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In order to determine reproducible and stable potential response conditions of the hydrogen ion in hydrofluoric acid solutions, lithium phosphate glass membranes of various constituents were developed. The glass membranes contained various metal oxides: Ag2O, Li2O, P2O5, MgO, BeO, WO2, and Al2O3. The response characteristics of the glass electrode depend strongly on the glass compositions. For the examination of the selectivity coefficient and the electrode function of hydrogen ion activities, the glass composition of 10 Ag2O : 20 Li2O : 50 P2O5 : 10 MgO : 10 WO2 is the most suitable one. The potential response is linear over the hydrogen ion activities of (100.3–10−4) mol/dm3, and has a slope of 44.5 mV/decade change in the hydrogen ion activity at 20 °C. The dynamic response time was within a minute in the range 10−1 to 10−4 mol/dm3. The intereference of the various cations on the activity of about 0.1 mol/dm3 can be ignored during the determination of the hydrogen ion activities at pH below 3. Physical and chemical properties, such as glass transition temperature, softening temperature, thermal expansion, membrane resistance, and chemical durability were measured and compared with those of other glasses.
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