ASTM D1252-06(R2020) pdf free download
ASTM D1252-06(R2020) pdf free download.Standard Test Methods for Chemical Oxygen Demand (Dichromate Oxygen Demand) of Water
1. Scope
1.1 These test methods cover the determination of the quantity of oxygen that certain impurities in water will consume, based on the reduction of a dichromate solution under specified conditions. The following test methods are included: Test Method A — Macro COD by Reflux Digestion and Titration Test Method B — Micro COD by Sealed Digestion and Spectrometry 1.2 These test methods are limited by the reagents employed to a maximum chemical oxygen demand (COD) of 800 mg/L. Samples with higher COD concentrations may be processed by appropriate dilution of the sample. Modified procedures in each test method (Section 15 for Test Method A, and Section 24 for Test Method B) may be used for waters of low COD content (<50 mg/L). 1.3 As a general rule, COD results are not accurate if the sample contains more than 1000 mg/LCl − . Consequently, these test methods should not be applied to samples such as seawaters and brines unless the samples are pretreated as described in Appendix X1. 1.4 This test method was used successfully on a standard made up in reagent water. It is the user’s responsibility to ensure the validity of these test methods for waters of untested matrices. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 8, 15.6, and 24.5. 1.7 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
5. Significance and Use
5.1 These test methods are used to chemically determine the maximum quantity of oxygen that could be consumed by biological or natural chemical processes due to impurities in water. Typically this measurement is used to monitor and control oxygen-consuming pollutants, both inorganic and organic, in domestic and industrial wastewaters. 5.2 The relationship of COD to other water quality param- eters such as TOC and TOD is described in the literature. 3
6. Interference and Reactivity
6.1 Chloride ion is quantitatively oxidized by dichromate in acid solution. (1.0 mg/L ofchloride is equivalent to 0.226 mg/L of COD.) As the COD test is not intended to measure this demand, concern for chloride oxidation is eliminated up to 1000 mg/L of chloride by complexing with mercuric sulfate. 6.1.1 Up to 40 000 mg/L chloride ion can be removed with a cation based ion exchange resin in the silver form as described in Appendix X1 when using Test Method B. Since this pretreatment was not evaluated during the interlaboratory study, the user of the test method is responsible to establish the precision and bias of each sample matrix. 6.2 Oxidizable inorganic ions, such as ferrous, nitrite, sulfite, and sulfides are oxidized and measured as well as organic constituents.
7. Reagents
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. All reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available. 4 7.2 Purity of Water—Unless otherwise indicated, reference to water shall be understood to mean reagent water that meets the purity specifications of Type I or Type II water, presented in Specification D1193.
