酸度計任務道理

      水溶液酸度的丈量普通用玻璃電極作為丈量電極，甘汞電極或銀－氯化銀電極作為參比電極。測定溶液的pH值時，將玻璃電極和參比電極(飽和甘汞電極)同時浸入待測溶液中構成電池，因為電極錯誤稱電位的存在，用玻璃電極測定溶液的pH值時普通接納比擬法測定，凡是是利用一個已知pH值的規范緩沖溶液停止定位，即用酸度計測定其電動勢E，由上式求常數E－，而后便可據待測溶液的E值，換算該溶液的pH值。酸度計已將電動勢E用pH值表現，是以可在酸度計上間接讀取溶液的pH值。現實測定時先測一個已知pH值的規范緩沖溶液獲得一讀數，而后測未知溶液獲得另外一讀數，兩讀數之差便是兩種溶液pH值之差。
      因為(wei)玻璃電(dian)(dian)(dian)極(ji)(ji)易碎，今朝的(de)酸度計多(duo)接納pH復合電(dian)(dian)(dian)極(ji)(ji)。pH復合電(dian)(dian)(dian)極(ji)(ji)是由(you)玻璃電(dian)(dian)(dian)極(ji)(ji)(丈量電(dian)(dian)(dian)極(ji)(ji))和銀－氯(lv)化(hua)(hua)(hua)銀電(dian)(dian)(dian)極(ji)(ji)(參比(bi)電(dian)(dian)(dian)極(ji)(ji))組合在(zai)(zai)一(yi)(yi)路的(de)塑殼(ke)可充式電(dian)(dian)(dian)極(ji)(ji)。玻璃電(dian)(dian)(dian)極(ji)(ji)頭(tou)部(bu)球(qiu)(qiu)(qiu)泡(pao)由(you)特別的(de)玻璃薄膜制成。它僅(jin)對H+有敏感感化(hua)(hua)(hua)，當它浸入(ru)被測(ce)溶(rong)(rong)(rong)液(ye)內(nei)，被測(ce)溶(rong)(rong)(rong)液(ye)中(zhong)H+與電(dian)(dian)(dian)極(ji)(ji)球(qiu)(qiu)(qiu)泡(pao)外(wai)表(biao)水化(hua)(hua)(hua)層中(zhong)H+停(ting)止離子(zi)互(hu)換，構成一(yi)(yi)電(dian)(dian)(dian)位(wei)(wei)，球(qiu)(qiu)(qiu)泡(pao)內(nei)層也同時有電(dian)(dian)(dian)位(wei)(wei)存(cun)在(zai)(zai)，是以球(qiu)(qiu)(qiu)泡(pao)表(biao)里發生一(yi)(yi)電(dian)(dian)(dian)位(wei)(wei)差(膜電(dian)(dian)(dian)位(wei)(wei))，此電(dian)(dian)(dian)位(wei)(wei)差隨外(wai)層被測(ce)溶(rong)(rong)(rong)液(ye)中(zhong)H+活度的(de)變(bian)更而轉變(bian)。因為(wei)電(dian)(dian)(dian)極(ji)(ji)外(wai)部(bu)的(de)溶(rong)(rong)(rong)液(ye)H+活度穩定，以是只需(xu)測(ce)出此電(dian)(dian)(dian)位(wei)(wei)差便可知(zhi)被測(ce)溶(rong)(rong)(rong)液(ye)的(de)pH值。