如果您无法下载资料，请参考说明：
1、部分资料下载需要金币，请确保您的账户上有足够的金币
2、已购买过的文档，再次下载不重复扣费
3、资料包下载后请先用软件解压，在使用对应软件打开
AOACOfficialMethod927.02CalciuminAnimalFeedDryAshMethodFinalAction(Applicationtomineralfeedsonly)Weigh2gfinelygroundsampleintoSiO2orporcelaindishandigniteinfurnacetoC-freeash,butavoidfusing.Boilresiduein40mLHCL(1+3)andfewdropsHNO3.Transferto250mLvolumetricflask,cool,dilutetovolume,andmixthoroughly.Pipet25mLclearliquidintobeaker,dilutetoca100mL,andadd2dropsmethylred,984.13B(c)(see4.2.09)AddNH4OH(1+1)dropwisetopH5.6,asshownbyintermediatebrownish-orange.Ifoverstepped,addHCL(1+3)withdroppertoorange.Add2moredropsHCL(1+3).Colorshouldnowbepink(pH2.5-3.0),notorange.Dilutetoca150mL,bringtoboil,andslowlyadd,withconstantstirring,10mLhotsaturated(4.2%)solutionof(NH4)2C2O4.Ifredchangestoorangeoryellow,addHCL(1+3)dropwiseuntilcoloragainchangestopink.Letstandovernightforprecipitatetosettle.Filtersupernatethroughquantitativepaper,Gooch,orfrittedglassfilter(finePyrexispreferable),andwashprecipitatethoroughlywithNH4OH(1+50).Placepaperorcruciblewithprecipitateinoriginalbeaker,andaddmixtureof125mLH2Oand5mLH2SO4.Heatto70andtitratewith0.1NKMnO4.940.35(seeA.1.10),tofirstslightpink.Presenceofpapermaycausecolortofadeinfews.Correctforblankandcalculate%Ca.References:JAOAC10,177(1927);19,93,574(1936);28,80(1945).CAS-7440-70-2(calcium)AOACOfficialMethod935.13CalciuminAnimalFeedWetAshMethod-FinalActionA.PreparationofSolution(Caution:SeeAppendixB,safetynotesonnitricacidandperchloricacid.)(a)Weigh2.5gsampleinto500or800mLKjeldahlflask.Add20-30mLHNO3andboilgently30-45mintooxidizealleasilyoxidizablematter.Coolsolutionsomewhatandadd10mL70-72%HCIO4.Boilverygently,adjustingflameasnecessary,untilsolutioniscolorlessornearlysoanddensewhitfumesappear.Useparticularcarenottoboiltodryness(Danger!)Atanytime.Coolslightly,add50mLH2O,andboiltodriveoutanyremainingNO2fumes.Cool,diluted,filterinto250mLvolumetricflask,dilutetovolume,andmixthoroughly.(b)Weigh2.5gfinelygroundsampleintoSiO2orporcelaindishandigniteasin942.05(see4.1.10).Add40mLHCL(1+3)andfewdropsHNO3tore
立即下载
