Designation:D859−16(Reapproved2021)´1StandardTestMethodforSilicainWater1ThisstandardisissuedunderthefixeddesignationD859;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.ε1NOTE—TheWTOcaveatwasaddededitoriallyinDecember2021.1.Scope1.1Thistestmethodcoversthedeterminationofsilicainwaterandwastewater;however,theanalystshouldrecognizethattheprecisionandaccuracystatementsforreagentwatersolutionsmaynotapplytowatersofdifferentmatrices.1.2Thistestmethodisacolorimetricmethodthatdeter-minesmolybdate-reactivesilica.Itisapplicabletomostwaters,butsomewatersmayrequirefiltrationanddilutiontoremoveinterferencesfromcolorandturbidity.Thistestmethodisusefulforconcentrationsaslowas20µg/L.1.3Thistestmethodcoversthephotometricdeterminationofmolybdate-reactivesilicainwater.Duetothecomplexityofsilicachemistry,theformofsilicameasuredisdefinedbytheanalyticalmethodasmolybdate-reactivesilica.Thoseformsofsilicathataremolybdate-reactiveincludedissolvedsimplesilicates,monomericsilicaandsilicicacid,andanundeter-minedfractionofpolymericsilica.1.4Theusefulrangeofthistestmethodisfrom20to1000µg/Latthehigherwavelength(815nm)and0.1to5mg/Latthelowerwavelength(640nm).Itisparticularlyapplicabletotreatedindustrialwaters.Itmaybeappliedtonaturalwatersandwastewatersfollowingfiltrationordilution,orboth.Forseawaterorbrines,thistestmethodisapplicableonlyifmatchedmatrixstandardsorstandardadditiontechniquesareemployed.1.5ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.6Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplic...
