Lub hauv paus ntsiab lus thiab cov yam ntxwv ntawm pH meter
1. pH ntsuas
Lub pH (acidity) meter yog ib qho cuab yeej rau kev txiav txim siab ua haujlwm ntawm H + hauv kev daws los ntawm txoj kev potentiometric. pH meter ntsuas tus nqi siv los qhia txog acidity lossis alkalinity ntawm kev daws nyob rau hauv cov nqe lus ntawm qhov tsis zoo logarithm ntawm cov concentration ntawm H + ions hauv cov tshuaj, piv txwv li, pH=ーlg [H +].
Lub pH meter peb siv yog tsim los ntawm ob ntu: lub ntsuas thiab electrode. Nyob rau hauv qhov tseeb ntsuas, lub electrode yog immersed nyob rau hauv cov tshuaj yuav tsum tau ntsuas, lub concentration ntawm H + ions nyob rau hauv cov tshuaj yog hloov mus rau hauv millivolt voltage teeb liab, input meter. Lub ntsuas yuav ua kom lub teeb liab, thiab tom qab logarithmic hloov dua siab tshiab rau pH, thiab tom qab ntawd los ntawm millivolt qib zaub ntsuas pH.
Lub pH meter siv lub iav electrode raws li ntsuas electrode thiab calomel electrode raws li siv electrode. Kev hloov pauv hauv hydrogen ion concentration tshwm sim los ntawm kev hloov pauv hauv cov iav electrode muaj peev xwm, ua rau muaj kev hloov pauv ntawm qhov muaj peev xwm ntawm nws cov electrode thiab calomel electrode, yuav tsum ua raws li cov qauv (2-6)
E=E0-2.3026RT/F............(2-6)
Hauv cov qauv:
E ib qho hluav taws xob muaj peev xwm, mV;
E0 tus qauv hluav taws xob electrode, mV;
R ib molar gas tas li;
T a Kelvin qhov kub thiab txias;
F a Faraday tas mus li.
Los ntawm cov mis (2-6) tuaj yeem pom nyob rau hauv kev ntsuas pH kub kuj yog ib qho tseem ceeb, hauv kev ntsuas yuav tsum tau them sai sai rau qhov ntsuas kub, thiab coj mus rau hauv tus account. Tam sim no siv pH electrodes rau composite electrodes, iav electrodes tau compounded ua ke nrog cov electrode ntawm calomel.
2. pH electrode
Electrode yog ib qho tseem ceeb ntawm qhov muaj pes tsawg leeg ntawm pH meter. Kev ntsuas pH yog los ntawm kev ntsuas ntawm electrodes, siv electrode tsim los ntawm cov roj teeb tshuaj ua kom tiav.
(1) pH ntsuas electrode, tseem hu ua pH qhov taw qhia electrode, hydrogen ion kev ua hauv cov tshuaj muaj cov lus teb, cov electrode muaj peev xwm hloov pauv. Yuav luag tag nrho cov pH niaj hnub siv iav electrodes raws li ntsuas electrode.
(2) Kev siv electrode (inert electrode), tsis muaj lus teb rau hydrogen ion kev ua hauv cov tshuaj. Hauv kev ntsuas pH, nws yog qhov muaj peev xwm tsis tu ncua ib nrab ntawm tes thiab pH ntsuas electrode tsim cov tshuaj cell, muab thiab tswj kom muaj peev xwm siv tau ruaj khov.
(3) Composite electrode yog kev sib xyaw ntawm pH ntsuas electrode thiab siv electrode. Composite electrode tsis cuam tshuam los ntawm oxidising thiab txo cov tshuaj, sib npaug sai dua, siv dav dua, qhov ntsuas pH tam sim no yog qhov tseem ceeb xws li electrodes. Seb lub iav qhov taw qhia electrode los yog iav puas electrode, yog ib zaj duab xis electrode, zaj duab xis muaj peev xwm thiab ntsuas hydrogen ion kev ua nyob rau hauv cov tshuaj yog lub zog-starter kev sib raug zoo, reflecting lub cim kev ua tau zoo ntawm cov zaj duab xis electrode, cov khoom los ntawm cov electrode nws tus kheej thiab cov siv cov xwm txheej ntawm qhov cuam tshuam, thiab cov txiaj ntsig ntawm lub luag haujlwm ntawm kev ntsuas.
