《工业分析 Industrial Analysis》课件-硅酸盐中氧化铝含量测定（双语）

项目七：硅酸盐分析任务三：硅酸盐质量分析硅酸盐中氧化铝含量测定课程：工业分析中文Scenario7:SilicateAnalysisTask3:QualityanalysisofsilicatesDeterminationofaluminacontentinsilicatesCourse:IndustrialAnalysisEglish水泥及其原料系统分析中，Al2O3的测定通常采用EDTA直接滴定法和CuSO4返滴定法，而且一般是在滴定Fe3＋之后的溶液中连续滴定铝。本方法已列入水泥化学分析方法国家标准。直接滴定法为基准法，适用于MnO含量

0.5%的试样；返滴定法为代用法，适用于MnO含量

0.5%的试样。中文Intheanalysisofcementanditsrawmaterialsystems,thedeterminationofAl2O3isusuallycarriedoutusingEDTAdirecttitrationmethodandCuSO4backtitrationmethod,andaluminumisgenerallycontinuouslytitratedinthesolutionaftertitrationwithFe3+.Thismethodhasbeenincludedinthenationalstandardforchemicalanalysismethodsofcement.Thedirecttitrationmethodisthereferencemethod,suitableforsampleswithMnOcontent>0.5%;Thebacktitrationmethodisasubstitutemethod,suitableforsampleswithMnOcontent<0.5%.Eglish一、直接滴定法在pH=3的溶液中，加热，使TiO2+水解为TiO（OH)2沉淀，以PAN和CuY为指示剂，用EDTA标液直接滴定溶液中的

Al3+。反应如下：1、方法原理中文一、DirecttitrationmethodInasolutionwithpH=3,heattohydrolyzeTiO2+intoTiO2(OH)2precipitate,andusePANandCuYasindicatorstodirectlytitrateAl3+inthesolutionwithEDTAstandardsolution.Thereactionisasfollows:1、MethodprincipleAttheendpoint,thesolutioncolour

changesfromredtoyellowred(yellow)Eglish2、测定步骤在滴定完铁的溶液中加入1~2滴溴酚蓝指示剂（2g/L），滴加氨水（1+2）至溶液出现蓝紫色，再滴加盐酸（1+2）至黄色，加入15mL醋酸-醋酸钠缓冲溶液（pH=3），加热至微沸，加入10滴CuY和2~3滴PAN指示剂，用EDTA标准溶液滴定至溶液变为亮黄色。中文2、MeasurementstepsAdd1-2dropsofbromophenolblueindicator(2g/L)tothesolutionaftertitrationofiron,addammoniawater(1+2)dropwiseuntilthesolutionturnsbluepurple,thenaddhydrochloricacid(1+2)dropwiseuntilitturnsyellow,add15mLofaceticacidsodiumacetatebuffersolution(pH=3),heatuntilslightlyboiling,add10dropsofCuYand2-3dropsofPANindicator,andtitratewithEDTAstandardsolutionuntilthesolutionturnsbrightyellow.Eglish3、结果计算中文3、ResultcalculationAl2O3%c--ConcentrationofEDTAstandardsolution,mol/LV--VolumeofEDTAstandardsolution,mLM--MolarmassofAl2O3,g/molm--Massofthesample,gEglish4、注意事项（1）最适宜pH2.5~3.5<2.5Al3+

与EDTA络合不完全；>3.5Al3+

水解倾向增大→偏低（2）指示剂用量PAN适量（2-3d）多→色深→不好观色（3）终点控制（如何控制终点？）由于Al3+与EDTA反应较慢，故经反复煮沸，反复滴定，一般3次即可出现稳定的黄色，其准确度满足生产要求。中文4、Note(1)ThemostsuitablepHis2.5~3.5pH<2.5:incompletecomplexationofAl3+withEDTA;pH>3.5:Al3+hydrolysistendencyincreases→measurementresultislow(2)Indicatordosage

AppropriateamountofPAN(2-3drops),excessive→solutioncolordark→difficulttoobservechangesinsolutioncolor(3)Endpointcontrol(howtocontroltheendpoint?)

DuetotheslowreactionbetweenAl3+andEDTA,itisnecessarytorepeatedlyboilandtitrate.Generally,astableyellowcolorcanappearafter3repetitions,anditsaccuracymeetsproductionrequirements.Eglish二、返滴定法1、方法原理中文二、Backtitrationmethod1、MethodprincipleSolutionaftertitrationofFe3+AddexcessEDTAheat,TransformingmostofAlintoAlYboilbrightpurpleAlltransformedintoAlYEglish2、反应中文2、Chemicalreactionsinvolved:(colourless)(residual)(blue-green)(yellow)(red)Excessive1dropThepurplishredcoloristheendpointEglish3、注意事项（1）终点颜色紫红色（好）终点颜色与过剩的EDTA量和所加PAN指示剂量有关中文3、Note(1)Colorofsolutionatendpoint:purplishredThecoloroftheendpointisrelatedtotheexcessamountofEDTAandtheindicateddosageofPANaddedToomuchEDTAortoolittlePANToolittleEDTAortoomuchPANEDTAexcessmoderateendpointBluepurpleorblueredPurplishredGenerallyEDTAexcess(i.e.reactionresidue)10-15mLEglish（2）pH调节时间加入过量EDTA，加热至70~80˚C，再调pH3.8~4.0Al3+与EDTA反应慢，过量EDTA及加热均提高反应速度

过量后并不直接调至pH3.8~4.0，目的是让大部分Al3+、TiO2+与EDTA络合，以防pH提高至3.8~4.0水解。中文(2)TimeforpHadjustmentAddexcessEDTAandheatto70-80℃,thenadjustthepHto3.8~4.0ThereactionbetweenAl3+andEDTAisslow,andexcessiveEDTAandheatingbothincreasethereactionrateAfteraddingexcessiveEDTA,thesolutionpHisnotdirectlyadjustedto3.8-4.0.ThepurposeistoallowmostAl3+andTiO2+tochelatewithEDTAtopreventhydrolysiswhenthepHisincreasedto3.8-4.0.Eglish（3）PAN使用PAN与Cu-PAN都不易溶于水，为增大其溶解度，配成PAN的酒精溶液，滴定时在热的条件下进行滴定，一般80-90˚C。（4）滴定的体积：保持在200mL以上，以降低Ca、Mn对测定的干扰。本法测得的是Al、Ti合量，要求高时，用光度法测出Ti量，扣除得准确铝量。中文(3)TheuseofPANPANandCuPANarenoteasilysolubleinwater.Toincreasetheirsolubility,analcoholsolutionofPANispreparedandtitratedunderhotconditions,typically80-90℃.(4)Volumeoftitration

Keepthesolutionvolumeabove200mLtoreducetheinterferenceofCaandMn