電位滴定法的介紹：
電(dian)(dian)位(wei)滴(di)定(ding)(ding)法(fa)(fa)是(shi)在滴(di)定(ding)(ding)過程中(zhong)通(tong)過測(ce)(ce)(ce)量電(dian)(dian)位(wei)變化(hua)以確(que)定(ding)(ding)滴(di)定(ding)(ding)終(zhong)(zhong)點(dian)(dian)(dian)的(de)(de)方(fang)法(fa)(fa)，和直(zhi)接(jie)(jie)電(dian)(dian)位(wei)法(fa)(fa)相比，電(dian)(dian)位(wei)滴(di)定(ding)(ding)法(fa)(fa)不(bu)需要(yao)準確(que)的(de)(de)測(ce)(ce)(ce)量電(dian)(dian)極(ji)電(dian)(dian)位(wei)值(zhi)，因(yin)此，溫度(du)(du)、液體接(jie)(jie)界電(dian)(dian)位(wei)的(de)(de)影響并(bing)不(bu)重要(yao)，其準確(que)度(du)(du)優于直(zhi)接(jie)(jie)電(dian)(dian)拉法(fa)(fa)，普通(tong)滴(di)定(ding)(ding)法(fa)(fa)是(shi)依靠指(zhi)示(shi)(shi)劑(ji)顏色變化(hua)來(lai)指(zhi)示(shi)(shi)滴(di)定(ding)(ding)終(zhong)(zhong)點(dian)(dian)(dian)，如果待(dai)(dai)測(ce)(ce)(ce)溶(rong)液有顏色或(huo)渾(hun)濁(zhuo)時，終(zhong)(zhong)點(dian)(dian)(dian)的(de)(de)指(zhi)示(shi)(shi)就(jiu)比較(jiao)困難，或(huo)者根本找不(bu)到(dao)合適的(de)(de)指(zhi)示(shi)(shi)劑(ji)。電(dian)(dian)位(wei)滴(di)定(ding)(ding)法(fa)(fa)是(shi)靠電(dian)(dian)極(ji)電(dian)(dian)位(wei)的(de)(de)突躍來(lai)指(zhi)示(shi)(shi)滴(di)定(ding)(ding)終(zhong)(zhong)點(dian)(dian)(dian)。在滴(di)定(ding)(ding)到(dao)達終(zhong)(zhong)點(dian)(dian)(dian)前后，滴(di)液中(zhong)的(de)(de)待(dai)(dai)測(ce)(ce)(ce)離子濃度(du)(du)往往連續變化(hua)n個(ge)數量級，引起(qi)電(dian)(dian)位(wei)的(de)(de)突躍，被測(ce)(ce)(ce)成(cheng)分的(de)(de)含量仍然(ran)通(tong)過消耗滴(di)定(ding)(ding)劑(ji)的(de)(de)量來(lai)計算(suan)。
使(shi)用不(bu)同的指(zhi)(zhi)示(shi)(shi)電(dian)極(ji)，電(dian)位滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)法可以(yi)進(jin)行(xing)酸堿滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)，氧化(hua)還原滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)，配(pei)合滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)和沉淀滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)。酸堿滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)時使(shi)用PH玻璃電(dian)極(ji)為指(zhi)(zhi)示(shi)(shi)電(dian)極(ji)，在(zai)氧化(hua)還原滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)中(zhong)，可以(yi)從鉑電(dian)極(ji)作(zuo)指(zhi)(zhi)示(shi)(shi)電(dian)極(ji)。在(zai)配(pei)合滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)中(zhong)，若(ruo)用EDTA作(zuo)滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)劑，可以(yi)用汞電(dian)極(ji)作(zuo)指(zhi)(zhi)示(shi)(shi)電(dian)極(ji)，在(zai)沉淀滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)中(zhong)，若(ruo)用硝酸銀滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)鹵素(su)離(li)子，可以(yi)用銀電(dian)極(ji)作(zuo)指(zhi)(zhi)示(shi)(shi)電(dian)極(ji)。在(zai)滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)過程(cheng)中(zhong)，隨著(zhu)滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)劑的不(bu)斷(duan)(duan)加入，電(dian)極(ji)電(dian)位E不(bu)斷(duan)(duan)發(fa)生變化(hua)，電(dian)極(ji)電(dian)位發(fa)生突躍(yue)時，說明滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)到(dao)達終(zhong)點(dian)。用微(wei)分曲(qu)(qu)線比普通滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)曲(qu)(qu)線更容易確定(ding)(ding)(ding)(ding)滴(di)(di)(di)(di)定(ding)(ding)(ding)(ding)終(zhong)點(dian)。
電位滴定(ding)的(de)步驟：
進(jin)行電(dian)位(wei)(wei)滴(di)定時，被(bei)測(ce)溶液(ye)中插入一個參比電(dian)極(ji)(ji)，一個指(zhi)示電(dian)極(ji)(ji)組成工作電(dian)池。隨著滴(di)定劑的(de)加入，由于發(fa)生(sheng)(sheng)化(hua)學反應，被(bei)測(ce)離(li)子濃度不斷(duan)變化(hua)，指(zhi)示電(dian)極(ji)(ji)的(de)電(dian)位(wei)(wei)也(ye)相應地變化(hua)。在等當點(dian)附(fu)近發(fa)生(sheng)(sheng)電(dian)位(wei)(wei)的(de)突躍(yue)。因此測(ce)量工作電(dian)池電(dian)動(dong)勢的(de)變化(hua)，可(ke)確(que)定滴(di)定終(zhong)點(dian)。
電位滴定的儀(yi)器(qi)：
電(dian)(dian)位滴(di)定的(de)基本儀器裝置包括滴(di)定管(guan)、滴(di)定池、指示電(dian)(dian)極、參比電(dian)(dian)極、攪拌器，測電(dian)(dian)動勢的(de)儀器。
電位滴(di)定(ding)法中(zhong)滴(di)定(ding)終點(dian)的確定(ding)：
用繪制(zhi)電(dian)位(wei)確定(ding)曲線(xian)(xian)的(de)方法。電(dian)位(wei)滴(di)定(ding)曲線(xian)(xian)即(ji)是(shi)隨著滴(di)定(ding)的(de)進(jin)行，電(dian)極(ji)電(dian)位(wei)值（電(dian)池電(dian)動勢）E對標準溶液(ye)的(de)加(jia)入體積V作圖(tu)的(de)圖(tu)形。根據作圖(tu)的(de)方法不同，電(dian)位(wei)滴(di)定(ding)曲線(xian)(xian)有三種類(lei)型(xing)，E-V曲線(xian)(xian)，普(pu)通電(dian)位(wei)滴(di)定(ding)曲線(xian)(xian)，拐(guai)(guai)點(dian)(dian)e即(ji)為等(deng)(deng)當點(dian)(dian)。拐(guai)(guai)點(dian)(dian)的(de)確定(ding)：作兩條與(yu)(yu)滴(di)定(ding)曲線(xian)(xian)相切的(de)45°傾斜的(de)直線(xian)(xian)，等(deng)(deng)分線(xian)(xian)與(yu)(yu)曲線(xian)(xian)的(de)交點(dian)(dian)即(ji)是(shi)拐(guai)(guai)點(dian)(dian)。Ee為等(deng)(deng)當點(dian)(dian)電(dian)位(wei)。Ve為等(deng)(deng)當點(dian)(dian)所需加(jia)的(de)標準溶液(ye)的(de)體積。電(dian)位(wei)突躍范圍和斜率越大，分析誤差就(jiu)越小(xiao)。
如果(guo)使用自(zi)動(dong)(dong)電位滴(di)定(ding)(ding)儀，在(zai)滴(di)定(ding)(ding)過(guo)程中可以自(zi)動(dong)(dong)繪(hui)出滴(di)定(ding)(ding)曲(qu)線，自(zi)動(dong)(dong)找(zhao)出滴(di)定(ding)(ding)終點，自(zi)動(dong)(dong)給(gei)出體積，滴(di)定(ding)(ding)快捷方便。
電位滴定法的特點和(he)應(ying)用：
電位滴(di)定(ding)法(fa)比起用(yong)(yong)指示劑(ji)的(de)容(rong)量分析法(fa)有(you)許多優越的(de)地(di)方，先可用(yong)(yong)于(yu)(yu)有(you)色(se)或(huo)混濁的(de)溶液(ye)的(de)滴(di)定(ding)，使(shi)用(yong)(yong)指示劑(ji)是不(bu)行的(de)；在(zai)沒(mei)有(you)或(huo)缺乏指示劑(ji)的(de)情況下，用(yong)(yong)此(ci)法(fa)解(jie)決；還可用(yong)(yong)于(yu)(yu)濃度較稀的(de)試液(ye)或(huo)滴(di)定(ding)反應進行不(bu)夠*的(de)情況；靈(ling)敏度和(he)準(zhun)確度高(gao)，并(bing)可實現自動化(hua)和(he)連(lian)續(xu)測定(ding)。因此(ci)用(yong)(yong)途十分廣泛。按(an)照(zhao)滴(di)定(ding)反應的(de)類型(xing)，電位滴(di)定(ding)可用(yong)(yong)于(yu)(yu)中和(he)滴(di)定(ding)（酸堿(jian)滴(di)定(ding)）沉淀滴(di)定(ding)，絡合滴(di)定(ding)，氧化(hua)還原滴(di)定(ding)。
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