電(dian)位滴定法的介(jie)紹(shao)：
電(dian)(dian)位(wei)(wei)滴(di)(di)定(ding)法(fa)(fa)是在滴(di)(di)定(ding)過(guo)程中通(tong)過(guo)測(ce)量(liang)電(dian)(dian)位(wei)(wei)變化(hua)以確定(ding)滴(di)(di)定(ding)終(zhong)(zhong)點(dian)的(de)方法(fa)(fa)，和直接(jie)電(dian)(dian)位(wei)(wei)法(fa)(fa)相(xiang)比，電(dian)(dian)位(wei)(wei)滴(di)(di)定(ding)法(fa)(fa)不(bu)(bu)需要(yao)準確的(de)測(ce)量(liang)電(dian)(dian)極(ji)電(dian)(dian)位(wei)(wei)值，因此，溫度、液(ye)(ye)體接(jie)界電(dian)(dian)位(wei)(wei)的(de)影響并不(bu)(bu)重要(yao)，其(qi)準確度優于直接(jie)電(dian)(dian)拉法(fa)(fa)，普(pu)通(tong)滴(di)(di)定(ding)法(fa)(fa)是依靠(kao)指(zhi)示(shi)劑(ji)顏色(se)變化(hua)來(lai)(lai)指(zhi)示(shi)滴(di)(di)定(ding)終(zhong)(zhong)點(dian)，如果待(dai)測(ce)溶(rong)液(ye)(ye)有顏色(se)或(huo)渾(hun)濁時，終(zhong)(zhong)點(dian)的(de)指(zhi)示(shi)就比較困難，或(huo)者(zhe)根本找不(bu)(bu)到合適的(de)指(zhi)示(shi)劑(ji)。電(dian)(dian)位(wei)(wei)滴(di)(di)定(ding)法(fa)(fa)是靠(kao)電(dian)(dian)極(ji)電(dian)(dian)位(wei)(wei)的(de)突躍來(lai)(lai)指(zhi)示(shi)滴(di)(di)定(ding)終(zhong)(zhong)點(dian)。在滴(di)(di)定(ding)到達終(zhong)(zhong)點(dian)前后，滴(di)(di)液(ye)(ye)中的(de)待(dai)測(ce)離子濃度往往連續變化(hua)n個數量(liang)級，引起電(dian)(dian)位(wei)(wei)的(de)突躍，被測(ce)成(cheng)分的(de)含量(liang)仍(reng)然通(tong)過(guo)消(xiao)耗(hao)滴(di)(di)定(ding)劑(ji)的(de)量(liang)來(lai)(lai)計算。
使用(yong)不同(tong)的指(zhi)示(shi)(shi)電(dian)(dian)(dian)極(ji)(ji)(ji)，電(dian)(dian)(dian)位滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)法可(ke)(ke)以(yi)進(jin)行酸(suan)(suan)堿滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)，氧(yang)(yang)化還原滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)，配(pei)合滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)和(he)沉(chen)淀滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)。酸(suan)(suan)堿滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)時使用(yong)PH玻璃電(dian)(dian)(dian)極(ji)(ji)(ji)為指(zhi)示(shi)(shi)電(dian)(dian)(dian)極(ji)(ji)(ji)，在氧(yang)(yang)化還原滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)中，可(ke)(ke)以(yi)從(cong)鉑電(dian)(dian)(dian)極(ji)(ji)(ji)作(zuo)(zuo)指(zhi)示(shi)(shi)電(dian)(dian)(dian)極(ji)(ji)(ji)。在配(pei)合滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)中，若用(yong)EDTA作(zuo)(zuo)滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)劑(ji)，可(ke)(ke)以(yi)用(yong)汞(gong)電(dian)(dian)(dian)極(ji)(ji)(ji)作(zuo)(zuo)指(zhi)示(shi)(shi)電(dian)(dian)(dian)極(ji)(ji)(ji)，在沉(chen)淀滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)中，若用(yong)硝酸(suan)(suan)銀滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)鹵素離子，可(ke)(ke)以(yi)用(yong)銀電(dian)(dian)(dian)極(ji)(ji)(ji)作(zuo)(zuo)指(zhi)示(shi)(shi)電(dian)(dian)(dian)極(ji)(ji)(ji)。在滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)過程(cheng)中，隨著滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)劑(ji)的不斷(duan)(duan)加入(ru)，電(dian)(dian)(dian)極(ji)(ji)(ji)電(dian)(dian)(dian)位E不斷(duan)(duan)發(fa)生變化，電(dian)(dian)(dian)極(ji)(ji)(ji)電(dian)(dian)(dian)位發(fa)生突(tu)躍時，說明滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)到達(da)終點。用(yong)微(wei)分(fen)曲線比(bi)普(pu)通滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)曲線更容易確(que)定(ding)(ding)(ding)(ding)(ding)(ding)(ding)滴定(ding)(ding)(ding)(ding)(ding)(ding)(ding)終點。
電位滴(di)定的步(bu)驟：
進行電(dian)(dian)位(wei)滴定時(shi)，被測(ce)溶(rong)液中插(cha)入一個(ge)參(can)比(bi)電(dian)(dian)極(ji)，一個(ge)指示電(dian)(dian)極(ji)組(zu)成工(gong)作(zuo)電(dian)(dian)池(chi)。隨著滴定劑的(de)加(jia)入，由于(yu)發生化(hua)學反應，被測(ce)離子濃度不斷(duan)變(bian)化(hua)，指示電(dian)(dian)極(ji)的(de)電(dian)(dian)位(wei)也相應地(di)變(bian)化(hua)。在等當點(dian)附近發生電(dian)(dian)位(wei)的(de)突躍(yue)。因此測(ce)量工(gong)作(zuo)電(dian)(dian)池(chi)電(dian)(dian)動勢的(de)變(bian)化(hua)，可確定滴定終(zhong)點(dian)。
電位滴(di)定的儀器：
電(dian)(dian)位滴(di)(di)定(ding)的基(ji)本儀器(qi)裝置包(bao)括(kuo)滴(di)(di)定(ding)管、滴(di)(di)定(ding)池、指示電(dian)(dian)極、參比電(dian)(dian)極、攪拌器(qi)，測電(dian)(dian)動勢的儀器(qi)。
電位滴定法中滴定終點的確定：
用繪(hui)制電位確(que)定(ding)(ding)(ding)曲(qu)線(xian)的(de)(de)方法。電位滴(di)(di)定(ding)(ding)(ding)曲(qu)線(xian)即(ji)是隨著滴(di)(di)定(ding)(ding)(ding)的(de)(de)進(jin)行，電極(ji)電位值(zhi)（電池電動勢）E對標準溶液(ye)的(de)(de)加入體(ti)積V作(zuo)(zuo)圖(tu)的(de)(de)圖(tu)形。根據(ju)作(zuo)(zuo)圖(tu)的(de)(de)方法不(bu)同，電位滴(di)(di)定(ding)(ding)(ding)曲(qu)線(xian)有三種(zhong)類型，E-V曲(qu)線(xian)，普(pu)通(tong)電位滴(di)(di)定(ding)(ding)(ding)曲(qu)線(xian)，拐(guai)點(dian)(dian)e即(ji)為(wei)等(deng)(deng)當(dang)點(dian)(dian)。拐(guai)點(dian)(dian)的(de)(de)確(que)定(ding)(ding)(ding)：作(zuo)(zuo)兩條(tiao)與(yu)滴(di)(di)定(ding)(ding)(ding)曲(qu)線(xian)相(xiang)切(qie)的(de)(de)45°傾斜的(de)(de)直(zhi)線(xian)，等(deng)(deng)分線(xian)與(yu)曲(qu)線(xian)的(de)(de)交點(dian)(dian)即(ji)是拐(guai)點(dian)(dian)。Ee為(wei)等(deng)(deng)當(dang)點(dian)(dian)電位。Ve為(wei)等(deng)(deng)當(dang)點(dian)(dian)所需加的(de)(de)標準溶液(ye)的(de)(de)體(ti)積。電位突(tu)躍范圍和斜率(lv)越大，分析誤差就(jiu)越小。
如果使(shi)用自(zi)動(dong)電(dian)位滴(di)(di)(di)定儀，在滴(di)(di)(di)定過程中(zhong)可(ke)以自(zi)動(dong)繪出(chu)滴(di)(di)(di)定曲線(xian)，自(zi)動(dong)找出(chu)滴(di)(di)(di)定終點，自(zi)動(dong)給出(chu)體積，滴(di)(di)(di)定快捷方(fang)便。
電位滴(di)定法的(de)特點和(he)應用：
電(dian)位滴(di)定(ding)(ding)(ding)法(fa)比起用(yong)(yong)指示劑(ji)的(de)(de)(de)容量分析法(fa)有許多優越的(de)(de)(de)地方，先(xian)可用(yong)(yong)于有色(se)或混濁的(de)(de)(de)溶液的(de)(de)(de)滴(di)定(ding)(ding)(ding)，使用(yong)(yong)指示劑(ji)是不行的(de)(de)(de)；在沒有或缺乏指示劑(ji)的(de)(de)(de)情(qing)況下，用(yong)(yong)此(ci)法(fa)解決；還(huan)(huan)可用(yong)(yong)于濃度(du)較稀的(de)(de)(de)試液或滴(di)定(ding)(ding)(ding)反(fan)應進行不夠*的(de)(de)(de)情(qing)況；靈敏度(du)和準確度(du)高，并(bing)可實(shi)現自動化和連續(xu)測定(ding)(ding)(ding)。因此(ci)用(yong)(yong)途十分廣泛。按照滴(di)定(ding)(ding)(ding)反(fan)應的(de)(de)(de)類型，電(dian)位滴(di)定(ding)(ding)(ding)可用(yong)(yong)于中和滴(di)定(ding)(ding)(ding)（酸堿滴(di)定(ding)(ding)(ding)）沉淀滴(di)定(ding)(ding)(ding)，絡(luo)合滴(di)定(ding)(ding)(ding)，氧化還(huan)(huan)原滴(di)定(ding)(ding)(ding)。
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