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191 IDENTIFICATIONTESTSGENERAL

UnderthisheadingareplacedteststhatarefrequentlyreferredtointhePharmacopeiafortheidentificationofofficialarticles.[NOTEThetestsarenotintendedtobeapplicabletomixturesofsubstancesunlesssospecified.]

AcetateWhenaceticacidoranacetateiswarmedwithsulfuricacidandalcohol,ethylacetate,recognizablebyitscharacteristicodor,isevolved.Withneutralsolutionsofacetates,ferricchlorideTSproducesadeepredcolorthatisdestroyedbytheadditionofmineralacids.

AluminumWith6Nammoniumhydroxide,solutionsofaluminumsaltsyieldagelatinous,whiteprecipitatethatisinsolubleinanexcessof6Nammoniumhydroxide.1NsodiumhydroxideorsodiumsulfideTSproducesthesameprecipitate,whichdissolvesinanexcessofeitherofthesereagents.

AmmoniumAmmoniumsaltsaredecomposedbytheadditionofanexcessof1Nsodiumhydroxide,withtheevolutionofammonia,recognizablebyitsodorandbyitsalkalineeffectuponmoistenedredlitmuspaperexposedtothevapor.Warmingthesolutionacceleratesthedecomposition.

AntimonyWithhydrogensulfide,solutionsofantimony(III)compounds,stronglyacidifiedwithhydrochloricacid,yieldanorangeprecipitateofantimonysulfidethatisinsolublein6Nammoniumhydroxide,butissolubleinammoniumsulfideTS.

BariumSolutionsofbariumsaltsyieldawhiteprecipitatewith2Nsulfuricacid.Thisprecipitateisinsolubleinhydrochloricacidandinnitricacid.Bariumsaltsimpartayellowishgreencolortoanonluminousflamethatappearsbluewhenviewedthroughgreenglass.

BenzoateInneutralsolutions,benzoatesyieldasalmoncoloredprecipitatewithferricchlorideTS.Inmoderatelyconcentratedsolutions,benzoatesyieldaprecipitateofbenzoicaciduponacidificationwith2Nsulfuricacid.Thisprecipitateisreadilysolubleinethylether.

BicarbonateSeeCarbonate.

BismuthWhendissolvedinaslightexcessofnitricacidorhydrochloricacid,bismuthsaltsyieldawhiteprecipitateupondilutionwithwater.Thisprecipitateiscoloredbrownbyhydrogensulfide,andtheresultingcompounddissolvesinawarmmixtureofequalpartsofnitricacidandwater.

BisulfiteSeeSulfite.

BorateTo1mLofaboratesolution,acidifiedwithhydrochloricacidtolitmus,add3or4dropsofiodineTSand3or4dropsofpolyvinylalcoholsolution(1in50):anintensebluecolorisproduced.Whenaborateistreatedwithsulfuricacid,

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methanolisadded,andthemixtureisignited,itburnswithagreenborderedflame.

BromideSolutionsofbromides,upontheadditionofchlorineTS,dropwise,liberatebromine,whichisdissolvedbyshakingwithchloroform,coloringthechloroformredtoreddishbrown.SilvernitrateTSproducesinsolutionsofbromidesayellowishwhiteprecipitatethatisinsolubleinnitricacidandisslightlysolublein6Nammoniumhydroxide.

CalciumSolutionsofcalciumsaltsforminsolubleoxalateswhentreatedasfollows.Toasolutionofthecalciumsalt(1in20)add2dropsofmethylredTS,andneutralizewith6Nammoniumhydroxide.Add3Nhydrochloricacid,dropwise,untilthesolutionisacidtotheindicator.UpontheadditionofammoniumoxalateTS,awhiteprecipitateisformed.Thisprecipitateisinsolublein6Naceticacidbutdissolvesinhydrochloricacid.Calciumsaltsmoistenedwithhydrochloricacidimpartatransientyellowishredcolortoanonluminousflame.

CarbonateCarbonatesandbicarbonateseffervescewithacids,evolvingacolorlessgasthat,whenpassedintocalciumhydroxideTS,producesawhiteprecipitateimmediately.Acoldsolution(1in20)ofasolublecarbonateiscoloredredbyphenolphthaleinTS,whileasimilarsolutionofabicarbonateremainsunchangedorisonlyslightlycolored.

ChlorateSolutionsofchloratesyieldnoprecipitatewithsilvernitrateTS.Theadditionofsulfurousacidtothismixtureproducesawhiteprecipitatethatisinsolubleinnitricacid,butissolublein6Nammoniumhydroxide.Uponignition,chloratesyieldchlorides,recognizablebyappropriatetests.Whensulfuricacidisaddedtoadrychlorate,decrepitationoccurs,andagreenishyellowgasisevolved.[CautionUseonlyasmallamountofchlorateforthistest,andexerciseextremecautioninperformingit.]

ChlorideWithsilvernitrateTS,solutionsofchloridesyieldawhite,curdyprecipitatethatisinsolubleinnitricacidbutissolubleinaslightexcessof6Nammoniumhydroxide.Whentestingamine(includingalkaloidal)hydrochloridesthatdonotrespondtotheabovetest,addonedropofdilutednitricacidand0.5mLofsilvernitrateTStoasolutionofthesubstancebeingexaminedcontaining,unlessotherwisedirectedinthemonograph,about2mgofchlorideionin2mL:awhite,curdyprecipitateisformed.Centrifugethemixturewithoutdelay,anddecantthesupernatantlayer.Washtheprecipitatewiththree1mLportionsofnitricacidsolution(1in100),anddiscardthewashings.AddammoniaTSdropwisetothisprecipitate.Itdissolvesreadily.Whenamonographspecifiesthatanarticlerespondstothetestfordrychlorides,mixthesolidtobetestedwithanequalweightofmanganesedioxide,moistenwithsulfuricacid,andgentlyheatthemixture:chlorine,whichisrecognizablebytheproductionofabluecolorwithmoistenedstarchiodidepaper,isevolved.

CitrateTo15mLofpyridineaddafewmgofacitratesalt,dissolvedorsuspendedin1mLofwater,andshake.Tothismixtureadd5mLofaceticanhydride,andshake:alightredcolorisproduced.

CobaltSolutionsofcobaltsalts(1in20)in3Nhydrochloricacidyieldaredprecipitatewhenheatedonasteambathwithanequalvolumeofahot,freshlypreparedsolutionof1nitroso2naphthol(1in10)in9Naceticacid.Solutionsofcobaltsalts,whensaturatedwithpotassiumchlorideandtreatedwithpotassiumnitriteandaceticacid,yieldayellowprecipitate.

CopperSolutionsofcupriccompounds,acidifiedwithhydrochloricacid,depositaredfilmofmetalliccopperuponabright,untarnishedsurfaceofmetalliciron.Anexcessof6Nammoniumhydroxide,addedtoasolutionofacupricsalt,producesfirstabluishprecipitateandthenadeepbluecoloredsolution.WithpotassiumferrocyanideTS,solutionsofcupricsaltsyieldareddishbrownprecipitate,insolubleindilutedacids.

HypophosphiteWhenstronglyheated,hypophosphitesevolvespontaneouslyflammablephosphine.HypophosphitesinsolutionyieldawhiteprecipitatewithmercuricchlorideTS.Thisprecipitatebecomesgraywhenanexcessofhypophosphiteispresent.Solutionsofhypophosphites,acidifiedwithsulfuricacid,andwarmedwithcupricsulfateTSyieldaredprecipitate.

IodideSolutionsofiodides,upontheadditionofchlorineTS,dropwise,liberateiodine,whichcolorsthesolutionyellowtored.Whenthesolutionisshakenwithchloroform,thelatteriscoloredviolet.TheiodinethusliberatedgivesabluecolorwithstarchTS.SilvernitrateTSproduces,insolutionsofiodides,ayellow,curdyprecipitatethatisinsolubleinnitricacidandin6Nammoniumhydroxide.

IronFerrousandferriccompoundsinsolutionyieldablackprecipitatewithammoniumsulfideTS.Thisprecipitateisdissolvedbycold3Nhydrochloricacidwiththeevolutionofhydrogensulfide.

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FerricSaltsAcidsolutionsofferricsaltsyieldadarkblueprecipitatewithpotassiumferrocyanideTS.Withanexcessof1Nsodiumhydroxide,areddishbrownprecipitateisformed.WithammoniumthiocyanateTS,solutionsofferricsaltsproduceadeepredcolorthatisnotdestroyedbydilutemineralacids.

FerrousSaltsSolutionsofferroussaltsyieldadarkblueprecipitatewithpotassiumferricyanideTS.Thisprecipitateisinsolublein3Nhydrochloricacidbutisdecomposedby1Nsodiumhydroxide.With1Nsodiumhydroxide,solutionsofferroussaltsyieldagreenishwhiteprecipitate,thecolorrapidlychangingtogreenandthentobrownwhenshaken.

LactateWhensolutionsoflactatesareacidifiedwithsulfuricacid,potassiumpermanganateTSisadded,andthemixtureisheated,acetaldehydeisevolved.Thiscanbedetectedbyallowingthevaportocomeintocontactwithafilterpaperthathasbeenmoistenedwithafreshlypreparedmixtureofequalvolumesof20%aqueousmorpholineandsodiumnitroferricyanideTS:abluecolorisproduced.

LeadWith2Nsulfuricacid,solutionsofleadsaltsyieldawhiteprecipitatethatisinsolublein3Nhydrochloricor2Nnitricacid,butissolubleinwarm1NsodiumhydroxideandinammoniumacetateTS.WithpotassiumchromateTS,solutionsofleadsalts,freeornearlyfreefrommineralacids,yieldayellowprecipitatethatisinsolublein6Naceticacidbutissolublein1Nsodiumhydroxide.

LithiumWithsodiumcarbonateTS,moderatelyconcentratedsolutionsoflithiumsalts,madealkalinewithsodiumhydroxide,yieldawhiteprecipitateonboiling.TheprecipitateissolubleinammoniumchlorideTS.Lithiumsaltsmoistenedwithhydrochloricacidimpartanintensecrimsoncolortoanonluminousflame.Solutionsoflithiumsaltsarenotprecipitatedby2Nsulfuricacidorsolublesulfates(distinctionfromstrontium).

MagnesiumSolutionsofmagnesiumsaltsinthepresenceofammoniumchlorideyieldnomorethanaslightlyhazyprecipitatewhenneutralizedwithammoniumcarbonateTS,butonthesubsequentadditionofdibasicsodiumphosphateTS,awhite,crystallineprecipitate,whichisinsolublein6Nammoniumhydroxide,isformed.

ManganeseWithammoniumsulfideTS,solutionsofmanganoussaltsyieldasalmoncoloredprecipitatethatdissolvesinaceticacid.

MercuryWhenappliedtobrightcopperfoil,solutionsofmercurysalts,freefromanexcessofnitricacid,yieldadepositthatuponrubbing,becomesbrightandsilveryinappearance.Withhydrogensulfide,solutionsofmercurycompoundsyieldablackprecipitatethatisinsolubleinammoniumsulfideTSandinboiling2Nnitricacid.

MercuricSaltsSolutionsofmercuricsaltsyieldayellowprecipitatewith1Nsodiumhydroxide.Theyyieldalso,inneutralsolutionswithpotassiumiodideTS,ascarletprecipitatethatisverysolubleinanexcessofthereagent.

MercurousSaltsMercurouscompoundsaredecomposedby1Nsodiumhydroxide,producingablackcolor.Withhydrochloricacid,solutionsofmercuroussaltsyieldawhiteprecipitatethatisblackenedby6Nammoniumhydroxide.WithpotassiumiodideTS,ayellowprecipitate,thatmaybecomegreenuponstanding,isformed.

NitrateWhenasolutionofanitrateismixedwithanequalvolumeofsulfuricacid,themixtureiscooled,andasolutionofferroussulfateissuperimposed,abrowncolorisproducedatthejunctionofthetwoliquids.Whenanitrateisheatedwithsulfuricacidandmetalliccopper,brownishredfumesareevolved.NitratesdonotdecolorizeacidifiedpotassiumpermanganateTS(distinctionfromnitrites).

NitriteWhentreatedwithdilutemineralacidsorwith6Naceticacid,nitritesevolvebrownishredfumes.Thesolutioncolorsstarchiodidepaperblue.

OxalateNeutralandalkalinesolutionsofoxalatesyieldawhiteprecipitatewithcalciumchlorideTS.Thisprecipitateisinsolublein6Naceticacidbutisdissolvedbyhydrochloricacid.HotacidifiedsolutionsofoxalatesdecolorizepotassiumpermanganateTS.

PermanganateSolutionsofpermanganatesacidifiedwithsulfuricacidaredecolorizedbyhydrogenperoxideTSandbysodiumbisulfiteTS,inthecold,andbyoxalicacidTS,inhotsolution.

PeroxideSolutionsofperoxidesslightlyacidifiedwithsulfuricacidyieldadeepbluecolorupontheadditionofpotassiumdichromateTS.Onshakingthemixturewithanequalvolumeofethyletherandallowingtheliquidstoseparate,theblue

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colorisfoundintheethyletherlayer.

Phosphate[NOTEWherethemonographspecifiestheidentificationtestforPhosphate,usethetestsfororthophosphates,unlesstheinstructionsspecifytheuseofthepyrophosphatetestsorindicatethattheproductistobeignitedbeforeperformingthetest.]WithsilvernitrateTS,neutralsolutionsoforthophosphatesyieldayellowprecipitatethatissolublein2Nnitricacidandin6Nammoniumhydroxide.WithammoniummolybdateTS,acidifiedsolutionsoforthophosphatesyieldayellowprecipitatethatissolublein6Nammoniumhydroxide.Thisprecipitatemaybeslowtoform.WithsilvernitrateTS,pyrophosphatesobtainedbyignitionyieldawhiteprecipitatethatissolublein2Nnitricacidandin6Nammoniumhydroxide.WithammoniummolybdateTS,ayellowprecipitatethatissolublein6Nammoniumhydroxideisformed.

PotassiumPotassiumcompoundsimpartavioletcolortoanonluminousflame,butthepresenceofsmallquantitiesofsodiummasksthecolorunlesstheyellowcolorproducedbysodiumisscreenedoutbyviewingthroughabluefilterthatblocksemissionat589nm(sodium)butistransparenttoemissionat404nm(potassium).Traditionally,cobaltglasshasbeenused,butothersuitablefiltersarecommerciallyavailable.Inneutral,concentratedormoderatelyconcentratedsolutionsofpotassiumsalts(dependinguponthesolubilityandthepotassiumcontent),sodiumbitartrateTSproducesawhitecrystallineprecipitatethatissolublein6Nammoniumhydroxideandinsolutionsofalkalihydroxidesandcarbonates.Theformationoftheprecipitate,whichisusuallyslow,isacceleratedbystirringorrubbingtheinsideofthetesttubewithaglassrod.Theadditionofasmallamountofglacialaceticacidoralcoholalsopromotestheprecipitation.

SalicylateInmoderatelydilutesolutionsofsalicylates,ferricchlorideTSproducesavioletcolor.Theadditionofacidstomoderatelyconcentratedsolutionsofsalicylatesproducesawhite,crystallineprecipitateofsalicylicacidthatmelts

between158 and161 .

SilverWithhydrochloricacid,solutionsofsilversaltsyieldawhite,curdyprecipitatethatisinsolubleinnitricacid,butisreadilysolublein6Nammoniumhydroxide.Asolutionofasilversalttowhich6NammoniumhydroxideandasmallquantityofformaldehydeTSareaddeddeposits,uponwarming,amirrorofmetallicsilveruponthesidesofthecontainer.

SodiumUnlessotherwisespecifiedinanindividualmonograph,prepareasolutiontocontain0.1gofthesodiumcompoundin2mLofwater.Add2mLof15%potassiumcarbonate,andheattoboiling.Noprecipitateisformed.Add4mLofpotassiumpyroantimonateTS,andheattoboiling.Allowtocoolinicewaterand,ifnecessary,rubtheinsideofthetesttubewithaglassrod.Adenseprecipitateisformed.Sodiumcompoundsimpartanintenseyellowcolortoanonluminousflame.

SulfateWithbariumchlorideTS,solutionsofsulfatesyieldawhiteprecipitatethatisinsolubleinhydrochloricacidandinnitricacid.WithleadacetateTS,neutralsolutionsofsulfatesyieldawhiteprecipitatethatissolubleinammoniumacetateTS.Hydrochloricacidproducesnoprecipitatewhenaddedtosolutionsofsulfates(distinctionfromthiosulfates).

SulfiteWhentreatedwith3Nhydrochloricacid,sulfitesandbisulfitesyieldsulfurdioxide,whichblackensfilterpapermoistenedwithmercurousnitrateTS.

TartrateDissolveafewmgofatartratesaltin2dropsofsodiummetaperiodatesolution(1in20).Addadropof1Nsulfuricacid,andafter5minutesaddafewdropsofsulfurousacidfollowedbyafewdropsoffuchsinsulfurousacidTS:areddishpinkcolorisproducedwithin15minutes.

ThiocyanateWithferricchlorideTS,solutionsofthiocyanatesyieldaredcolorthatisnotdestroyedbymoderatelyconcentratedmineralacids.

ThiosulfateWithhydrochloricacid,solutionsofthiosulfatesyieldawhiteprecipitatethatsoonturnsyellow,andsulfurdioxide,whichblackensfilterpapermoistenedwithmercurousnitrateTS.TheadditionofferricchlorideTStosolutionsofthiosulfatesproducesadarkvioletcolorthatquicklydisappears.

ZincInthepresenceofsodiumacetate,solutionsofzincsaltsyieldawhiteprecipitatewithhydrogensulfide.Thisprecipitateisinsolubleinaceticacid,butisdissolvedby3Nhydrochloricacid.AmmoniumsulfideTSproducesasimilarprecipitateinneutralandinalkalinesolutions.WithpotassiumferrocyanideTS,zincsaltsinsolutionyieldawhiteprecipitatethatisinsolublein3Nhydrochloricacid.

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AuxiliaryInformationStaffLiaison:AntonioHernandezCardoso,B.S.,Scientist,LatinAmericanSpecialistExpertCommittee:(GC05)GeneralChapters05USP29NF24Page2550PharmacopeialForum:VolumeNo.27(6)Page3349PhoneNumber:13018168308