1、Designation:D125206(Reapproved 2012)1Standard Test Methods forChemical Oxygen Demand(Dichromate Oxygen Demand)ofWater1This standard is issued under the fixed designation D1252;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year
2、of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1NOTEEditorial corrections made throughout in
3、June 2013.1.Scope1.1 These test methods cover the determination of thequantity of oxygen that certain impurities in water willconsume,based on the reduction of a dichromate solutionunder specified conditions.The following test methods areincluded:Test Method A 2 Macro COD by Reflux Digestion and Tit
4、rationTest Method B 2 Micro COD by Sealed Digestion and Spectrometry1.2 These test methods are limited by the reagents employedto a maximum chemical oxygen demand(COD)of 800 mg/L.Samples with higher COD concentrations may be processed byappropriate dilution of the sample.Modified procedures ineach t
5、est method(Section 15 for Test MethodAand Section 24for Test Method B)may be used for waters of low CODcontent(50 mg/L).1.3 As a general rule,COD results are not accurate if thesample contains more than 1000 mg/LCl.Consequently,thesetest methods should not be applied to samples such asseawaters and
6、brines unless the samples are pretreated asdescribed in Appendix X1.1.4 This test method was used successfully on a standardmade up in reagent water.It is the users responsibility toensure the validity of these test methods for waters of untestedmatrices.1.5 This standard does not purport to address
7、 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 Section 8,15.6,and 24.5.2.Ref
8、erenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3223 Test Method for Total Mercury in WaterD3370 Practices for Sampling Water from C
9、losed ConduitsD5905 Practice for the Preparation of Substitute WastewaterE60 Practice for Analysis of Metals,Ores,and RelatedMaterials by SpectrophotometryE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible Spectrophotometers3.Terminology3.1 DefinitionsFor definitions of
10、 other terms used in thesetest methods,refer to Terminology D1129.3.2 The term“oxygen demand”(COD)in these test meth-ods is defined in accordance with Terminology D1129 asfollows:3.2.1 oxygen demandthe amount of oxygen required un-der specified test conditions for the oxidation of water borneorganic
11、 and inorganic matter.4.Summary of Test Methods4.1 Most organic and oxidizable inorganic substances pres-ent in water are oxidized by a standard potassium dichromatesolution in 50%sulfuric acid(vol/vol).The dichromateconsumed(Test Method A)or tri-valent chromium produced(Test Method B)is determined
12、for calculation of the CODvalue.4.2 The oxidation of many otherwise refractory organics isfacilitated by the use of silver sulfate that acts as a catalyst inthe reaction.1These test methods are under the jurisdiction of ASTM Committee D19 onWater and are the direct responsibility of Subcommittee D19
13、.06 on Methods forAnalysis for Organic Substances in Water.Current edition approved June 15,2012.Published June 2012.Originallyapproved in 1953.Last previous edition approved in 2006 as D1252 06.DOI:10.1520/D1252-06R12E01.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact A
14、STM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.3 These test methods provide for
15、 combining the reagentsand sample in a manner that minimizes the loss of volatileorganic materials,if present.4.4 The oxidation of up to 1000 mg/L of chloride ion isinhibited by the addition of mercuric sulfate to form stable andsoluble mercuric sulfate complex.A technique to remove up to40 000 mg/L
16、 chloride is shown in Appendix X1 for TestMethod B.The maximum chloride concentration that may betolerated with the procedure for low COD,Test Method A(15.10),has not been established.4.5 The chemical reaction involved in oxidation of materialsby dichromate is illustrated by the following reaction withpotassium acid phthalate(KC8H5O4):41 H2SO4110 K2Cr2O712 KC8H5O410 Cr2SO4!3111 K2SO4116 CO2146 H2OSince 10 mol of potassium dichromate has the same oxida-tion power as 15 mol of oxygen,the equivalen
