pH response of nonhygroscopic glasses

Abstract

Electrodes prepared from glasses of low hygros copicity, high electrical resistance and unsatisfactory pH response in aqueous solutions have been inves tigated in an effort to deter-!l1i~e if .th e~r failure to develop t he f~ll pH response is due merely to a lack of sensitivity of t he lI1dlcatll1g lI1strument or t o a real faIlure of these glasses to respond to hydrogen-ion activity. By increasing t he sensitivit y of the indicating instrument and decreasing t he t hickness of the electrode membrane in order to lower the electrical resistance, many of t hese glasses have been shown t o develop the full pH response of 59 millivolts per pH at 25° C . Howe ver, theoret ical and experimental evidence indicates that glasses below a limit ing hygros copicity probably do not develop full pH response regardless of the thickness of the glass membrane t he resistance of t he ele ctrode, or the sensitivity of t he indicating instrument. In fact glas~ electrodes for which the thickness, electric resis tance, and surface are retained esse~tially unaltered t hroughout t h e experime nts exhibit large departures from t he hydrogen electrode upon the progressive removal of water .

Evaluation of the kinetic parameters of the hydrogen electrode reaction from the analysis of the equilibrium polarisation resistance

“…(7) was evaluated from a H + ¼ 10 ÀpH . As pH(1M H 2 SO 4 ) ¼ 0.0125, 14 then a H + ¼ 0.9716. The result obtained from the non-linear regression of the reported data using eqn.…”