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AOAC Official 966.20 Moisture in Liquid Molasses Titrimetric First Action 19

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AOAC Official 966.20 Moisture in Liquid Molasses Titrimetric First Action 1966 Final Action 1967_AOAC.rar,AOAC Official 966.20 Moisture in Liquid Molasses Titrimetric First Action 19

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44.2.03AOAC Official Method 966.20Moisture in Liquid MolassesTitrimetric MethodFirst Action 1966Final Action 1967(Not applicable to molasses which fails to dissolve in methanolwithintimespecifiedforstabilityofendpointoftitrationassembly.)A. ApparatusBuretwithautomaticzero;reservoirforreagent;magneticstirrer;titration vessel (300 mL Berzelius beaker with stopcock attached toside at bottom for withdrawing excess solution is recommended),electrodes, and circuitry for deadstop end point detection. All open-ingsmustbetightlyclosedorprotectedwithdryingtubestopreventcontamination from atmospheric H2O. Various titration assembliesmay be obtained commercially or one may be assembled.Assemble titration apparatus and follow manufacturers instruc-tions,settingfordirecttitration.Settimertogive30sendpoint.Addenough dry methanol to cover electrodes on electrode probes andturn on stirrer. Adjust speed to obtain good stirring without splash-ing.Donotletstirrerbarcontactelectrodes.Titrateuntilsatisfactoryend point is reached. Apparatus newly assembled or not recentlyusedmayrequirerepetitionofthissteptodryoutsystem.Teststabil-ityofendpointobtainedbycontinuingtitrationbeyondfirst30sendpoint for same time required for titration of test sample. Generallyendpointshouldpersistfor5mintobeassuredofprotectionfromat-mospheric H2O contamination and instability of reagents.B. Reagents(Caution: See Appendix B, safety notes on methanol, pyridine,and sulfur dioxide.)(a) KarlFischerreagent.Availablecommerciallyorprepareasfollows: Dissolve 133 g I2in 425 mL dry pyridine in dryglass-stoppered bottle. Add 425 mL dry methanol or ethylene glycolmonomethyl ether. (Less trouble with stopcock leakage is obtainedwithethyleneglycolmonomethylether.)Coolto4Cinicebathandbubblein102105gSO2.Mixwellandletstand12h.Reagentisrea-sonably stable, but restandardize for each series of determinations.(b) Anhydrous methanol.Reagent grade methanol containing0.1% H2O. Prepare by distilling over Mg.C. DeterminationAdd ca 120 mg H2O from weighing pipet or other suitable deviceand titrate with Karl Fischer reagent.Calculate C = mg H2O/mL reagent.For titration of molasses, C = ca 5 mg/mL. Weigh molasses esti-mated to give 2040 mL titer into titration apparatus and titrate.H2O, % =C mL reagentg molasses 10Drain excess liquid and repeat with succeeding test portions. Iftime lapse occurs between titrations, adjust liquid in titration vesseltoendpoint