試劑滴定度的標定
① 卡爾-費休試劑的滴定度的標定準確與否,直接關係到樣品測定的準確度,測試環境條件的不同,儀器整套裝置的密封性能如何,對卡爾-費休試劑滴定度的變化影響很大,尤其對測量準確度要求較高的樣品。
② didingdudebiaodingyuanzeshangyinggaizaimeitiandeyangpinceshiqianjinxing。didingdudebiaodingkeyiyongjuyouyidinghanshuiliangdebiaozhunwuzhi,youxiebiaozhunwuzhishiyetide,yonganpeipingfengzhuang。meicixiaohaoyizhi,zhunquedugao,feiyongjiaoda:youxiebiaozhunwuzhishigutide,zhunquedugao,duibiaozhunwuzhidebaocunyaoqiujiaogao。yidanshouchaojiumafan。zuijiandanshiyongdeshichunshuibiaoding。yongweiliangzhusheqizhunqueyiqushuiliang,yibanqu10到30微升水量進行標定,連續重複幾次,取平均值,求出卡爾-費休試劑的滴定度。但是有些試驗室的檢驗人員對卡爾-費fei休xiu試shi劑ji滴di定ding度du標biao定ding的de含han義yi並bing不bu完wan全quan清qing楚chu,或huo者zhe是shi不bu負fu責ze任ren的de惰duo性xing,竟jing然ran會hui發fa生sheng一yi瓶ping試shi劑ji從cong開kai啟qi使shi用yong進jin行xing一yi次ci滴di定ding度du標biao定ding以yi後hou一yi直zhi到dao試shi劑ji用yong完wan,幾ji個ge月yue時shi間jian內nei的de樣yang品pin測ce試shi始shi終zhong用yong一yi個ge滴di定ding度du的de標biao定ding值zhi,顯xian然ran其qi中zhong是shi有you較jiao大da誤wu差cha的de。
③ 卡爾-費(fei)休(xiu)試(shi)劑(ji)的(de)滴(di)定(ding)度(du)隨(sui)著(zhe)使(shi)用(yong)時(shi)間(jian)的(de)延(yan)長(chang)是(shi)逐(zhu)步(bu)變(bian)化(hua)的(de),相(xiang)對(dui)於(yu)第(di)一(yi)天(tian)的(de)滴(di)定(ding)度(du)誤(wu)差(cha)也(ye)隨(sui)之(zhi)變(bian)大(da)。由(you)此(ci)可(ke)見(jian)幾(ji)個(ge)月(yue)內(nei)一(yi)直(zhi)使(shi)用(yong)最(zui)初(chu)的(de)滴(di)定(ding)度(du)來(lai)計(ji)算(suan)測(ce)定(ding)值(zhi),對(dui)測(ce)定(ding)值(zhi)的(de)誤(wu)差(cha)是(shi)較(jiao)大(da)的(de)。所(suo)以(yi)應(ying)該(gai)經(jing)常(chang)對(dui)卡(ka)爾(er)-費休試劑進行滴定度的標定,應該根據試驗室的環境溫度、濕度和儀器的封閉性能,以及試驗的要求,合理確定對卡爾-費休試劑滴定度標定的時間間隔,以確保測量的準確度。而樣品測量的準確度與產品的質量有關。
安全防護
① 卡爾-費休試劑主要由碘、二氧化硫、bidinghejiachunzuchengderongye。qizhongdeeryanghualiuyubidinghuifaxingjiqiang,duirentideweihaihenda,caozuoshiyingzailianghaodetongfengtiaojianxiajinxing。youqishizaihuanshijishi,yaozhuyipaifeng,yifangzhiyouhaiqitixirentinei。bingdaishangfanghuyanjingyurujiaoshoutao,bimianyouhaishijijiansayanjingheshoushang,yidanfashengshijijiansayanjingheshoushangyaolijiyongliudongshuichongxi,yanzhongzhejisongyiyuanzhiliao。
② 但dan實shi際ji情qing況kuang是shi有you些xie操cao作zuo人ren員yuan對dui該gai試shi劑ji的de危wei害hai性xing認ren識shi不bu足zu,在zai無wu任ren何he防fang護hu措cuo施shi的de條tiao件jian下xia,將jiang試shi劑ji隨sui意yi倒dao進jin倒dao出chu,滿man屋wu異yi味wei而er渾hun然ran不bu顧gu,自zi我wo保bao護hu意yi識shi問wen題ti有you待dai加jia強qiang。
試劑的應用
① 卡爾-費休試劑對新鮮度要求很高,購買卡爾-費休試劑要注意生產日期,要根據使用量即買即用。並要避光保存,才能延長保存期。
② 目前有不含吡啶的卡爾-費休試劑問世,解決了含吡啶試劑有刺鼻異味的問題,但是測定中發現含吡啶的卡爾-費休試劑終點的突變較明顯,試劑到終點時的顏色是微棕黃色,根據經驗憑肉眼能預測到終點即將到來,而不含吡啶的卡爾-feixiushijizhongdiandetubianbumingxian,shijidaozhongdianshideyanseshishenzongse。liangzhedexuanzekegenjushiyangdehanshuiliangyijiduiyangpinjiancezhunqueduyaoqiudebutongerding。duihanshuiliangdi、檢測準確度要求高的樣品建議選用含吡啶的卡爾-費休試劑。反之則用不含吡啶的卡爾-費休試劑。
③ 無水甲醇作為樣品的溶解劑,適用範圍很廣。一般的有機化合物、飽和或不飽和的碳氫化合物以及一般的無機化合物、酸性氧化物、部bu分fen有you機ji和he無wu機ji的de鹽yan都dou能neng適shi用yong。但dan是shi部bu分fen酮tong和he醛quan類lei樣yang品pin不bu能neng用yong甲jia醇chun反fan應ying。如ru發fa現xian反fan應ying不bu能neng中zhong斷duan,無wu終zhong點dian,反fan應ying連lian續xu進jin行xing時shi,應ying該gai考kao慮lv到dao是shi否fou有you副fu反fan應ying這zhe個ge問wen題ti。當dang產chan生sheng副fu反fan應ying時shi,其qi實shi隻zhi需xu要yao幾ji分fen鍾zhong的de反fan應ying,卻que一yi直zhi進jin行xing。此ci時shi可ke用yong乙yi二er醇chun甲jia醚mi代dai替ti甲jia醇chun,可ke得de更geng為wei恒heng定ding的de滴di定ding體ti積ji,而er且qie可ke在zai不bu使shi用yong任ren何he專zhuan門men技ji術shu下xia測ce定ding某mou些xie酮tong和he醛quan類lei化hua工gong產chan品pin的de水shui分fen。
④ PH值過高、樣品堿性過高等,也會引起副反應,即連續反應,而無終點出現。此時,PH值過高可用緩衝溶液調節PH值,堿性過高加入甲苯酸、水楊酶,可緩和堿性溶液,但不能用醋酸。在進行甲醇水分滴定時(俗稱空白滴定),如反應瓶中的顏色逐步由無色至深棕色,儀器仍無終點出現,應視為卡爾-費休試劑已失效,即應更換試劑。
電極汙染與保養
① dianjishishuifencedingyideguanjianbujian,dianjibiaomiandewurankezhijiedaozhilingmindujiangdi,youxiedianjichangqiyingyongyuyouzhiyangpindefenxi,dianjibiaomianbeiyouzhiwuranhou,lingmindujiangdi,shidedianjiduizhongdiandepanduanchidun,zaochengkaer-費fei休xiu試shi劑ji過guo量liang,終zhong點dian反fan應ying時shi溶rong液ye顏yan色se偏pian深shen,此ci時shi必bi須xu清qing洗xi電dian極ji。盡jin管guan肉rou眼yan看kan不bu到dao電dian極ji上shang的de汙wu染ran物wu,但dan可ke以yi觀guan察cha到dao反fan應ying遲chi鈍dun,直zhi接jie影ying響xiang測ce量liang準zhun確que性xing。因yin此ci電dian極ji使shi用yong一yi段duan時shi期qi以yi後hou必bi須xu清qing洗xi,但dan是shi有you相xiang當dang一yi部bu分fen操cao作zuo人ren員yuan沒mei考kao慮lv到dao這zhe個ge問wen題ti。
② 當(dang)靈(ling)敏(min)度(du)降(jiang)低(di),電(dian)極(ji)受(shou)汙(wu)染(ran)嚴(yan)重(zhong)時(shi)。可(ke)用(yong)紙(zhi)沾(zhan)一(yi)點(dian)丙(bing)酮(tong)擦(ca)電(dian)極(ji),但(dan)必(bi)須(xu)小(xiao)心(xin)翼(yi)翼(yi),還(hai)必(bi)須(xu)等(deng)丙(bing)酮(tong)揮(hui)發(fa)完(wan)全(quan)後(hou)方(fang)可(ke)使(shi)用(yong)。或(huo)者(zhe)將(jiang)電(dian)極(ji)浸(jin)入(ru)稀(xi)硝(xiao)酸(suan)溶(rong)液(ye)中(zhong)24小時,然後取出,用清水漂洗,濾紙拭淨。也可以用重鉻酸鉀溶液清洗l分fen鍾zhong以yi活huo化hua電dian極ji。在zai特te殊shu情qing況kuang下xia,如ru樣yang品pin等deng著zhe要yao分fen析xi,清qing洗xi電dian極ji時shi間jian不bu容rong許xu,這zhe時shi可ke用yong急ji辦ban法fa解jie決jue電dian極ji汙wu染ran的de事shi件jian。用yong極ji細xi的de沙sha紙zhi輕qing輕qing擦ca磨mo電dian極ji兩liang端duan,濾lv紙zhi拭shi淨jing後hou,即ji可ke見jian效xiao。
③ 儀器如有一段時期不用,就應將泵管及液路內的卡爾-費休試劑全部排完,以避免因試劑揮發引起結晶而堵塞管路;同樣反應瓶內的卡爾-費fei休xiu試shi劑ji也ye應ying排pai完wan,電dian極ji拭shi淨jing。在zai儀yi器qi的de檢jian測ce中zhong經jing常chang可ke發fa現xian,有you關guan操cao作zuo人ren員yuan樣yang品pin測ce定ding結jie束shu,電dian源yuan一yi關guan了le事shi,對dui儀yi器qi的de維wei護hu和he保bao養yang與yu測ce量liang的de準zhun確que度du應ying該gai是shi密mi切qie相xiang關guan的de問wen題ti意yi識shi不bu足zu。
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