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1、2.PROPERTIESANDANALYTICALPROCEDURES2.1IdentityElementolarsenic(As)isamemberofGroup15oftheperiodictable,withnitrogen,phosphorus,antimonyandbismuth.Ithasanatomicnumberof33andanatomicmassof74.91.TheChemicalAbstractService(CAS),NationalInstituteforOccupationalSafetyandHealthRegistryofToxicEf
2、fectsofChemicals(RTECS),HazardousSubstancesDataBank(HSDB),EuropeanCommission,andUNtransportclassnumbersare7440-38-2,HSB509,CG05235000,033-001-00-XandUN1558,respectively.Thismonographdealswitharsenicandinorganicandorganicarseniccompounds,cxccptarsine(AsH3),forwhichaConciseInternationalChe
3、micalAssessmentDocument(C1CAD)isbeingprepared.2.2ChemicalandphysicalpropertiesofarseniccompoundsArsenicisametalloidwidelydistributedintheearth"scrust.Itcancxistinfourvalencystates;-3,0,+3,and+5.Instronglyreducingenvironments,elementalarsenicandarsine(-3)canexist.Undermoderatelyreducingco
4、nditions,arsenite(+3)maybethedominantform,butarsenate(+5)isgenerallythestableoxidationstateinoxygenatedenvironments.Arsenicanditscompoundsoccurincrystalline,powder,amorphousorvitreousforms.Theyusuallyoccurintracequantiticsinallrock,soil,waterandair.However,concentrationsmaybehigherincert
5、ainareasasaresultofweatheringandanthropogenicactivitiesincludingmetalminingandsmelting,fossilfuelcombustionandpesticideuse.ArsenicalsaltsexhibitarangeofaqueoussolubililiesdependingonthepHandtheionicenvironment.Therearcmanyarseniccompoundsofenviromnentaiimportancc.Rcprcscntativcmarincarse
6、nic-containingcompounds,ofwhichsomearefoundinterrestrialsystems,areshowninTable1;theirmolecularstructuresareshownFig.1.OtherarseniccompoundsdiscussedinthetextarelistedinTable2.Table1・(seeFig.Naturallyoccurringinorganic1forstructures[1]-[22])andorganicAsspeciesCASNo.NameSynonymsStructurea
7、rsenate[1]arsenite[2]124-58-3methvlarsonicacid7monomethylcirsonicacid,MMA[3]4964-14-1trimcthylarsincoxide[5]27742-38-7tetramethylarsoniumion[6]64436-13-1arsenobetaine[7]39895-81-3arsenocholine[8]dimethylarsinoylribosides⑼-[19]trialkylarsonioribosides[20],[21]dimethylarsin
