ASTM_D_6697_-_01.pdf

Designation:D 6697 01An American National StandardStandard Test Method forDetermination for Chemical Oxygen Demand(Manganese III1Oxygen Demand)of Water2This standard is issued under the fixed designation D 6697;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 colorimetric determinationof the quantity of oxygen that certain impurities in water willconsume,based on the reduction of a manganese III solutionunder specified conditions.This standard method does not usecharacteristic heavy metal reagents,thus eliminating environ-mental and disposal concerns apparent in other methods.1.2 This test method determines chemical oxygen demandcolorimetrically using manganese III to obtain a visible colorintensity inversely proportional to the chemical oxygen de-mand of the sample.Analytical test kits conforming to thesemethods are available commercially in ranges from 80 to 1,000mg/L(ppm)chemical oxygen demand.It is the users respon-sibility to ensure the validity of these test methods for theirspecific samples and matrices.1.3 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.For specific hazardstatements,see Sections 9 and 12.2.Referenced Documents2.1 ASTM Standards:D 596 Practice for Reporting Results of Analysis of Water3D 1129 Terminology Relating to Water3D 1193 Specification for Reagent Water3D 2777 Determination of Precision and Bias of ApplicableMethods of Water3D 5789 Writing Quality Control Specifications for StandardTest Methods for Organic Constituents3D 5905 Practice for the Preparation of Substitute Wastewa-ter4E 60 Practice for Photometric and SpectrophotometricMethods for Chemical Analysis of Metals5E 275 Practice for Describing and Measuring Performanceof Ultraviolet,Visible and Near Infrared Spectrophotom-eters63.Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method referto Definitions D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 oxygen demand,nthe amount of oxygen required,under specified test conditions for the oxidation of water-borneorganic and inorganic matter.3.2.2 MSDS,nMaterial Safety Data Sheet;should beincluded with all reagents.4.Summary of Test Method4.1 This test method consists of oxidation of sample organicmatter by manganese III,a strong,chemical oxidant,andsubsequent measure of the organic matter oxygen equivalent.Manganese III changes quantitatively from purple towardscolorless when it reacts with organic matter.The reactionmechanism of the method is illustrated by the followingequation,using potassium hydrogen phthalate as an example:KC8H5O41 7.5 O2 8 CO21 2 H2O 1 KOH4.1.1 Manganese III typically oxidizes about 80%of theorganic compounds.Studies have shown that the reactions arereproducible,and test results can be correlated empirically tobiochemical oxygen demand(BOD)values and hexavalentchromium COD tests.None of the above oxygen demand testsprovide 100%oxidation of all organic compounds.4.2 Calibration is based on the oxidation of potassium acidphthalate(KHP),which is adequate for most applications.Thiscalibration may be developed by the user,or the manufacturermay provide a curve that it has developed for its instruments.A different response may be seen in analyzing various waste-waters.Special waste streams or classes will require a separatecalibration to obtain a direct mg/L COD reading or to generatea correction factor for the precalibrated KHP response.Thesample digestion time can be extended for up to four hours forsamples that are difficult to oxidize.1Trivalent Manganese.2This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.06 on Methods forAnalysis forOrganic Substances in Water.Current edition approved July 10,2001.Published October 2001.3Annual Book of ASTM Standards,Vol 11.01.4Annual Book of ASTM Standards,Vol 11.02.5Annual Book of ASTM Standards,Vol 03.05.6Annual Book of ASTM Standards,Vol 14.01.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.4.3 For samples containing chloride,pretreatment to re-move chloride interference is necessary.Chloride removal isaccomplished by introducing the sample to the chloride re-moval agent before sample reaction with the manganese IIIoxidant.4.4 The sample,with or without chloride-removal pretreat-ment,is introduced carefully into a screw-top tube thatcontains the manganese III reagent.4.5 The sealed tube is heated in a heating block at 165 6 2C for two