項目四：肥料分析任務四：鉀肥分析鉀肥分析課程：工業(yè)分析中文Scenario4:FertilizerAnalysisTask4:PotassiumfertilizeranalysisPotassiumfertilizeranalysisCourse:IndustrialAnalysisEglish一、鉀肥種類中文一、TypesofpotassiumfertilizersPotassiumfertilizerisdividedintotwocategories:naturalpotassiumfertilizerandchemicalpotassiumfertilizer.Thesumofwater-solubleandweaklyacidsolublepotassiumsaltsinpotassiumfertilizeriscalledeffectivepotassium.Thesumofavailablepotassiumandinsolublepotassiumsaltsiscalledtotalpotassium.ThepotassiumcontentofpotassiumfertilizerisexpressedasK2O.Whenmeasuringeffectivepotassium,asamplesolutionisusuallypreparedbydissolvingitinhotwater;Ifthesamplecontainsweaklyacidsolublepotassiumsalt,dissolvetheavailablepotassiuminhotwaterwithasmallamountofhydrochloricacidadded.Whenmeasuringthetotalpotassiumcontent,thesamplesolutionisgenerallypreparedbystrongaciddissolutionoralkalimeltingmethod.Eglish二、鉀肥分析方法

鉀肥中有效鉀的測定方法有四苯硼酸鉀重量法、四苯硼酸鈉容量法和火焰光度法。四苯硼酸鉀重量法和四苯硼酸鈉容量法簡便、準確、快速，適用于含氧化鉀量較高的鉀肥測定。當試樣中含氧化鉀小于2%時，采用火焰光度法測定。中文二、Analysismethodsforpotassiumfertilizer

Themethodsfordeterminingeffectivepotassiuminpotassiumfertilizersincludepotassiumtetraphenylborategravimetricmethod,sodiumtetraphenylboratevolumetricmethod,andflamephotometry.

Thepotassiumtetraphenylborategravimetricmethodandthesodiumtetraphenylboratevolumetricmethodaresimple,accurate,andfast,suitableforthedeterminationofpotassiumfertilizerswithhighpotassiumoxidecontent.Whenthecontentofpotassiumoxideinthesampleislessthan2%,flamephotometryisusedformeasurement.Eglish（1）方法原理：在堿性條件下加熱消除試樣溶液中銨離子的干擾，加入乙二胺四乙酸二鈉(EDTA)螯合其他微量陽離子，以消除干擾分析結(jié)果的陽離子。在微堿性介質(zhì)中，四苯硼酸鈉與鉀反應生成四苯硼酸鉀沉淀，過濾、干燥沉淀并稱量。1、四苯硼酸鉀重量法中文(1)Methodprinciple:Heatunderalkalineconditionstoeliminatetheinterferenceofammoniumionsinthesamplesolution,andadddisodiumethylenediaminetetraacetate(EDTA)tochelateothertracecationstoeliminatetheinterferenceofcationsintheanalysisresults.Inaslightlyalkalinemedium,sodiumtetraphenylboratereactswithpotassiumtoformpotassiumtetraphenylborateprecipitate,whichisfiltered,dried,andweighed.1、potassiumtetraphenylborategravimetricmethodwhiteEglish（2）結(jié)果計算氧化鉀(K2O)的含量w1以質(zhì)量分數(shù)%表示，按下式計算：中文（2）resultcalculation

Thecontentofpotassiumoxide(K2O)w1isexpressedasamassfraction%,andiscalculatedusingthefollowingformula:Eglish（3）實驗步驟

移取一定量溶液，加入EDTA溶液及酚酞指示液，在攪拌下逐滴加入氫氧化鈉溶液至紅色出現(xiàn)并過量1mL。加熱微沸15min(此時溶液應保持紅色)。在攪拌下逐滴加入四苯硼鈉溶液，在流水中迅速冷卻至室溫并放置15min。先過濾上層清液，再用洗滌液轉(zhuǎn)移沉淀至過濾器中，用洗滌液洗滌沉淀，干燥稱量。中文（3）Procedure

Takeacertainamountofsamplesolution,addEDTAsolutionandphenolphthaleinindicatorsolution,andaddsodiumhydroxidesolutiondropwisewhilestirringuntilredappearsand1mLofexcesssodiumhydroxidesolutionisadded.Heatandslightlyboilfor15minutes(atthistime,thesolutionshouldremainred).Addsodiumtetraphenylboratesolutiondropwisewhilestirring,rapidlycooltoroomtemperatureinflowingwater,andletitstandfor15minutes.Firstfiltertheupperclearliquid,thentransfertheprecipitatetothefilterwithwashingsolution.Washtheprecipitatewithwashingsolution,dryit,andweighit.Eglish（1）方法原理在堿性條件下加熱消除試樣溶液中銨離子的干擾，加入乙二胺四乙酸二鈉(EDTA)消除其他陽離子的干擾，在微堿性介質(zhì)中，以過量的四苯硼酸鈉與鉀反應生成四苯硼酸鉀沉淀，過濾，濾液中過量的四苯硼酸鈉以達旦黃作指示劑，用季銨鹽返滴至溶液由黃變成明顯的粉紅色2、四苯硼酸鈉容量法中文(1)MethodprincipleHeatunderalkalineconditionstoeliminatetheinterferenceofammoniumionsinthesamplesolution,andadddisodiumethylenediaminetetraacetate(EDTA)toeliminatetheinterferenceofothercations.Inaslightlyalkalinemedium,excesssodiumtetraphenylboratereactswithpotassiumtoformpotassiumtetraphenylborateprecipitate,whichisfiltered.Finally,usingdanhuangasanindicator,theexcesssodiumtetraphenylborateistitratedbackwithquaternaryammoniumsaltuntilthesolutionchangesfromyellowtoaclearpinkcolor2、sodiumtetraphenylboratevolumetricmethodEglish其化學反應為：B(C6H5)4-＋K+＝KB(C6H5)4↓Br[N(CH3)3·C16H33]＋NaB(C6H5)4＝B(C6H5)4·N(CH3)3C16H33↓＋NaBr中文Itschemicalreactionis:B(C6H5)4-＋K+＝KB(C6H5)4↓Br[N(CH3)3·C16H33]＋NaB(C6H5)4＝B(C6H5)4·N(CH3)3C16H33↓＋NaBrEglish(2)方法討論

鉀肥中常見的雜質(zhì)有鈣、鎂、鋁、鐵等硫酸鹽和磷酸鹽，雖與四苯硼酸鈉不反應，但滴定體系在堿性溶液中進行，可能會生成氫氧化物、磷酸鹽等沉淀，因吸附作用影響滴定，故加EDTA掩蔽。中文(2)Methoddiscussion

Commonimpuritiesinpotassiumfertilizerincludesulfatesandphosphatessuchascalcium,magnesium,aluminum,andiron.Theydonotreactwithsodiumtetraphenylborate.Becausetitrationiscarriedoutinanalkalinesolution,thesesaltsubstancesmayformprecipitatessuchashydroxidesandphosphates,whichaffecttitrationduetotheadsorptioneffectoftheprecipitate.Therefore,EDTAshouldbeaddedtomasktheseions.Eglish3、火焰光度法（1）方法原理試樣經(jīng)硫酸-過氧化氫消煮，使待測液在火焰高溫激發(fā)下輻射出鉀元素的特征光譜，其強度與溶液中鉀的濃度成正比，從鉀標準溶液所作的工作曲線上即可查出待測液的鉀濃度。（2）結(jié)果計算總鉀含量(K2O)計)的質(zhì)量百分數(shù)。中文3、Flamephotometry(1)MethodprincipleAfterthesampleisdigestedwithsulfuricacidhydrogenperoxide,thesolutiontobetestedisexcitedbyahigh-temperatureflameandemitsacharacteristicspectrumofpotassiumelement.Theintensityofthespectrallinesisproportion