ASTM_D_2761_-_89_1998.pdf

Designation:D 2761 89(Reapproved 1998)Standard Test Method forAnalysis of Sodium Triphosphate by the Simplified IonExchange Method1This standard is issued under the fixed designation D 2761;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of ortho-,pyro-,and meta-phosphates in sodium triphosphate.It dependson direct flow elutriation through a column of ion exchangeresin.1.2 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.Material SafetyData Sheets are available for reagents and materials.Reviewthem for hazards prior to usage.2.Summary of Test Method2.1 A sample of sodium triphosphate is introduced into anion exchange resin column.The phosphate ions diffuse into theresin phase and are held by the resin cation.The anions are thenselectively eluted from the column using different strengths ofpotassium chloride solutions.The ions with the least affinityare eluted first:ortho-,pyro-,tri-,and meta-phosphate,respec-tively.Colorimetric molybdenum blue procedure is used forphosphorus pentoxide(P2O5)determinations of each fractionand of total phosphate.3.Apparatus3.1 Separatory Funnel,500-mL.3.2 Ion Exchange Column,31 cm(310 mm)long with28-mm inside diameter.23.3 Tubing,vinyl(Tygon),14-in.(6-mm)inside diameter,38-in.(9-mm)outside diameter.3.4 Tubing,capillary,chemical-resistant glass,112-mm in-side diameter,7-mm outside diameter.3.5 PhotometerA spectrophotometer or filter photometersuitable for measurements at approximately 650 nm with10-mm cells.4.Reagents4.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused,provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.4.2 Purity of WaterUnless otherwise indicated,referencesto water shall be understood to mean distilled water or water ofequal purity.4.3 Ammonium Molybdate Solution(100 g/L)Dissolve100 g of ammonium molybdate(NH4)6Mo7O244H2O)inwater and dilute to 1 L.4.4 Ion-Exchange ResinAnion-exchange resin,100 to200-mesh,chloride form(Caution,see Note 1).NOTE1Caution:This method as written is based on the use ofanalytical grade Dowex AG-1X8 anion exchange resin.Comparableresults may not be obtained with other resins.4.5 Phosphate,Standard Solution(1 mL 5 0.05 mgP2O5)Dissolve 0.9568 g of potassium dihydrogen phosphate(KH2PO4)in water and dilute to 500 mL.Transfer 25 mL ofthis solution to a 500-mL volumetric flask and dilute tovolume.4.6 Potassium Acetate Stock Buffer Solution(78.5 g/L,pH 5 5.0)Dissolve 78.5 g of potassium acetate(KC2H3O2)in water and dilute to 1 L.Adjust the pH to 5.0 with glacialacetic acid.NOTE2Add a pinch of mercuric iodide to inhibit mold growth.4.7 Potassium Chloride Solution(22.35 g/L)Dissolve22.35 g of potassium chloride(KCl)in water,add 5 mL of thestock buffer solution(4.6),and dilute to 1 L(Note 2).4.8 Potassium Chloride Solution(44.7 g/L)Dissolve 44.7g of KCl in water,add 5 ml of the stock buffer solution(4.6),and dilute to 1 L(Note 2).1This test method is under the jurisdiction of ASTM Committee D-12 on Soapsand Other Detergents and is the direct responsibility of Subcommittee D12.14 onAnalysis of Inorganic Alkaline Detergents.Current edition approved May 26,1989.Published July 1989.Originallypublished as D 2761 68.Last previous edition D 2761 85.2Fischer and Porter,Model No.1320,available from Scientific Glass ApparatusCo.,Inc.,Bloomfield,NJ as Catalog No.C4225X,has been found satisfactory forthis purpose.3Reagent Chemicals,American Chemical Society Specifications,AmericanChemical Society,Washington,DC.For suggestions on the testing of reagents notlisted by the American Chemical Society,see Analar Standards for LaboratoryChemicals,BDH Ltd.,Poole,Dorset,U.K.,and the United States Pharmacopeiaand National Formulary,U.S.Pharmacopeial Convention,Inc.(USPC),Rockville,MD.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.NOTICE:This standard has either been superseded and replaced by a new version or discontinued.Contact ASTM International(www.astm.org)for the latest information.4.9 Potassium Chloride Solution(74.5 g/L)Dissolve 74.5g of KCl in water,add 5 mL of stock buffer solution(4.6),anddilute to 1 L(Note 2).4.10 Reducing SolutionDissolve 7 g of sodium sulf