ASTM D1126-2017 Standard Test Method for Hardness in Water《水硬度的标准试验方法》.pdf

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1、Designation: D1126 12D1126 17Standard Test Method forHardness in Water1This standard is issued under the fixed designation D1126; 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 in

2、dicates 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.1. Scope*1.1 This test method covers the determination of hardness in water by titrat

3、ion. This test method is applicable to waters that areclear in appearance and free of chemicals that will complex calcium or magnesium. The lower detection limit of this test methodis approximately 2 to 5 mg/L as CaCO3; the upper limit can be extended to all concentrations by sample dilution. It is

4、possibleto differentiate between hardness due to calcium ions and that due to magnesium ions by this test method.1.2 This test method was tested on reagent water only. It is the users responsibility to ensure the validity of the test methodfor waters of untested matrices.1.3 The values stated in SI

5、units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, he

6、alth, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of Inte

7、rnational Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1066 Practice for Sampling SteamD1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Det

8、ermination of Precision and Bias of Applicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis3. Terminology3.1 DefinitionsFor definitions of terms used

9、 in this test method, refer to Terminology D1129.3.1 Definitions:3.1.1 For definitions of terms used in this standard, refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 equivalent per million (epm), na unit chemical equivalent weight of solute per million unit weigh

10、ts of solution.3.2.2 laboratory control sample (LCS), na solution with certified hardness.4. Summary of Test Method4.1 Calcium and magnesium ions in water are sequestered by the addition of disodium ethylenediamine tetraacetate. The endpoint of the reaction is detected by means of Chrome Black T3, w

11、hich has a red color in the presence of calcium and magnesiumand a blue color when they are sequestered.1 This test method is under the jurisdiction ofASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.Current edition approved March

12、 1, 2012Dec. 1, 2017. Published March 2012December 2017. Originally approved in 1950. Last previous edition approved in 20072012as D1126 02 (2007)D1126 12.1. DOI: 10.1520/D1126-12.10.1520/D1126-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at

13、 serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 3Hydroxy4-(1hydroxy-2napththyl) azo-7nitro1 naphthalenesulfonic acid, sodium salt, Color Index 14645.This document is not an ASTM standard and is intended only to

14、 provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof

15、 the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 Hardness salts in

16、 water, notably calcium and magnesium, are the primary cause of tube and pipe scaling, which frequentlycauses failures and loss of process efficiency due to clogging or loss of heat transfer, or both.5.2 Hardness is caused by any polyvalent cations, but those other than Ca and Mg are seldom present

17、in more than traceamounts. The term hardness was originally applied to water in which it was hard to wash; it referred to the soap-wasting propertiesof water. With most normal alkaline water, these soap-wasting properties are directly related to the calcium and magnesiumcontent.6. Interferences6.1 T

18、he substances shown in Table 1 represent the highest concentrations that have been found not to interfere with thisdetermination.6.2 The test method is not suitable for highly colored waters, which obscure the color change of the indicator.7. Reagents7.1 Purity of ReagentsReagent grade chemicals sha

19、ll be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society.4 Othergrades may be used, provided it is first ascertained that the reagent is of sufficiently high purit

20、y to permit its use without lesseningthe accuracy of the determination.4 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed bythe American Chemical Society, see Annual Standards for Laboratory

21、Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.TABLE 1 Freedom of Reaction from InterferencesSubstanceMaximumConcentrationWithoutInterferencein the TotalHardnessTest, mg/LMaximumConcentrati

22、onWithoutInterferencein the CalciumHardnessTest, mg/LAluminum, Al+ + + 20 5Ammonium, NH4 + A 2 000Bicarbonate, HCO3 . 500Bromine, Br . 2Cadmium, Cd+ + 20 .Carbonate, CO3 1 000 50Chloride, Cl 10 000 .Chlorine, Cl . 2Chromate, CrO4 500 500Cobalt, Co + + 0.3 .Copper, Cu + + 20 2Iron, ferric, Fe + + 10B

23、 20Iron, ferrous, Fe + + 10B 20Lead, Pb + 20 5Manganese, Mn + + 1C 10CNickel, Ni + + 0.5D .Nitrate, NO3 500 500Nitrite, NO2 500 500Phosphate, PO4 100 .Silicate, SiO3 200 100Strontium, Sr + + E ESulfate, SO4 10 000 10 000Sulfite, SO3 500 500Tannin, Quebracho 200 50Tin, stannic, Sn + + 10 5Tin, stanno

24、us, Sn + + 10 5Zinc, Zn + 20 5A No data are available.B Iron will not interfere in concentrations up to 200 mg/L. However, the red color ofthe end point may return in about 30 s.C Manganese will not interfere in concentrations up to 10 mg/L if a few crystals ofK4Fe(CN)63H2O are added to the buffer i

25、mmediately before use.D Accurate results can be obtained in the presence of 1 mg/L nickel, but the endpoint is slow under these conditions.E If strontium is present, it will be titrated with calcium and magnesium.D1126 1727.2 Purity of WaterUnless otherwise indicated, reference to water shall be und

26、erstood to mean reagent water conforming toSpecification D1193, Type I. Other reagent water types may be used provided it is first ascertained that the water is of sufficientlyhigh purity to permit its use without adversely affecting the precision and bias of the test method. Type II water was speci

27、fied atthe time of round robin testing of this test method.7.3 Ammonium Hydroxide Solution (1 + 4)Mix 1 volume of NH4OH (sp gr 0.90) with 4 volumes of water.7.4 Buffer SolutionPrepare the buffer solution in three steps as follows:7.4.1 Dissolve 40 g of sodium tetraborate (Na2B4O710H2O) in 800 mL of

28、water.7.4.2 Dissolve 10 g of sodium hydroxide (NaOH), 10 g of sodium sulfide (Na2S9H2O), and 10 g of potassium sodium tartrate(KNaC4O64H2O) in 100 mL of water.7.4.3 When cool mix the two solutions and add 1 g of magnesium disodium ethylenediamine tetraacetate, having amagnesium-to-EDTA mole ratio of

29、 1 to 1. Make up to 1 L with water. Keep the solution bottle stoppered when not in use. Thereagent will be effective for at least 1 month.7.5 Calcium Solution, Standard (1 mL = 0.20 mg CaCO3)Dissolve 0.2000 g of CaCO3 in 3 to 5 mL of HCl (1 + 4). Diluteto 1 L with water.7.6 Calcium IndicatorUse powd

30、ered hydroxynaphthol blue,5 or grind solid hydroxynaphthol blue to 40 to 50 mesh size.7.7 Hardness IndicatorThe hardness indicator can be prepared, stored, and used in liquid or powder form.7.7.1 Hardness Indicator SolutionDissolve 0.5 g of Chrome Black T3 in 50 mL of diethanolamine or triethanolami

31、ne. Storethe solution in a dark-colored bottle. This solution has a storage life of several months.7.7.2 Hardness Indicator PowderGrind 0.5 g of Chrome Black T3 with 100 g of powdered sodium chloride. Use adark-colored bottle for storage. The powder has a storage life of at least 1 year.7.8 Hydrochl

32、oric Acid (1 + 4)Mix 1 volume of concentrated hydrochloric acid (sp gr 1.19) with 4 volumes of water.7.9 Disodium Ethylenediamine Tetraacetate (Na2H2 EDTA) Solution, Standard (1 mL = 1.0 mg CaCO3)Dissolve 3.8 g ofdisodium ethylenediamine tetraacetate dihydrate in approximately 800 mL of water. Adjus

33、t the pH of the solution to 10.5 withNaOH solution (50 g/L). Determine the concentration of this solution using the standard calcium (7.5) solution, and that procedurein Section 9 that will be used for the sample analysis (9.1, 9.2, or 9.3). Adjust the concentration of the EDTA so that 1 mL willbe e

34、quivalent to 1.0 mg of CaCO3. Store the standard EDTA in polyethylene, plastic, or hard rubber bottles and restandardizemonthly.7.10 Sodium Hydroxide Solution (50 g/L)Dissolve 50 g of sodium hydroxide in water and dilute to 1 L.8. Sampling8.1 Collect the sample in accordance with Practice D1066 or P

35、ractices D3370 as applicable.9. Procedure9.1 HardnessMeasure 50 mL of clear sample into an opaque white container or a clear colorless container utilizing a whitebackground. Adjust the pH of the sample to 7 to 10 by adding NH4OH (7.3) solution or HCl (7.8) solution. Add 0.5 mL of buffer(7.4) solutio

36、n, and approximately 0.2 g of hardness (7.7) indicator powder or 2 drops of liquid and stir.Add standard Na2H2EDTA(7.9) solution slowly from a burette with continuous stirring until the color changes from red to blue. Complete the titration within5 min after the buffer addition. If the titration req

37、uires more than 20 mL of the titrating solution, dilute the sample and repeat thetest.9.2 Low HardnessDetermine low-hardness values (0.5 to 5.0 ppm as CaCO3) in accordance with 9.1, but use a 100 mLsampleand titrate by means of micro-burette. When employing a 100-mL sample, add twice the quantity of

38、 the reagents as indicated in9.1.9.3 Calcium HardnessMeasure 50 mL of the sample into an opaque white container, or a clear colorless container utilizinga white background.Add 2 mL of NaOH (7.10) solution and stir.Add approximately 0.2 g of calcium (7.6) indicator and stir.Addstandard Na2H2EDTA (7.9

39、) solution slowly from a burette with continuous stirring until the color changes from red to royal blue.Complete the titration within 5 min after the NaOH addition. If the titration requires more than 15 mL of the titrating solution,dilute the sample and repeat the test.10. Calculations10.1 Calcula

40、te the hardness, epm, of the sample as follows:Hardness, epm520 C/S (1)5 3Hydroxy-4 (2hydroxy4 sulfo1 naphthyl) azo2, 7naphthalenedisulfonic acid, trisodium salt.D1126 173where:epm = equivalent parts per million; milliequivalents per litre,C = standard Na2H2EDTA solution added in titrating hardness,

41、 mL, andS = sample taken, mL.10.1.1 Calculate the calcium hardness, epm, of the sample as follows:Calcium hardness,epm520 D/S (2)where:epm = equivalent parts per million; milliequivalents per litre,D = standard Na2H2EDTA solution added in titrating calcium hardness, mL, andS = sample taken for test,

42、 mL.10.1.2 Calculate the magnesium hardness, epm, of the sample as follows:Magnesium hardness,epm5E2F (3)where:epm = equivalent parts per million; milliequivalents per litre,E = hardness, epm, andF = calcium hardness, epm.10.2 Calculate the hardness as calcium carbonate of the sample as follows:Hard

43、ness,mg/Las CaCO351000 C1/S1 (4)where:C1 = standard Na2H2EDTA solution added in titrating hardness, mL, andS1 = sample taken, mL.10.2.1 Calculate the calcium hardness as calcium carbonate of the sample as follows:Calcium hardness,mg/Las CaCO351000 D1/S1 (5)where:D1 = standard Na2H2EDTA solution adde

44、d in titrating calcium hardness, mL, andS1 = sample taken, mL.10.2.2 Calculate the magnesium hardness as calcium carbonate of the sample as follows:Magnesium hardness,mg/Las CaCO35G2H (6)where:G = hardness, mg/L as CaCO3, andH = calcium hardness, mg/L as CaCO3.11. Precision and Bias611.1 The single

45、operation and overall precision of the total hardness test method within its designated range for 6 laboratories,which include a total of 6 operators analyzing each sample on 3 different days may be expressed as follows:6 Supporting data have been filed at ASTM International Headquarters and may be

46、obtained by requesting Research Report RR:D19-1125. Contact ASTM CustomerService at serviceastm.org.TABLE 2 Statistical Information, Total HardnessAmountAdded,mg/LAmountFound,mg/LBias % Bias StatisticallySignificant11.0 11.4 + 0.4 + 3.6 No45.0 46.3 + 1.3 + 2.9 No206. 206. 0.0 0.0 No450. 453. + 3. +

47、0.7 NoCalcium Hardness6.2 6.1 0.1 1.6 No25.0 24.9 0.1 0.4 No125. 126. + 1.0 + 0.8 No250. 250. 0.0 0.0 NoD1126 174So 50.0047 X10.40 (7)ST 50.0078 X11.80 (8)where:So = pooled single-operator precision, mg/L,St = overall precision, mg/L, andX = hardness concentration, mg/L.11.2 The single operator and

48、overall precision of the calcium hardness test method within its designated range for 6 laboratories,which include a total of 6 operators analyzing each sample on 3 different days may be expressed as follows:So 50.0052 X10.37 (9)St 50.025 X10.61 (10)where:So = pooled single-operator precision, mg/LS

49、t = overall precision, mg/L, andX = calcium hardness concentration, mg/L.11.3 Recoveries of known amounts of hardness and calcium hardness in a series of prepared standards for the same laboratoriesand operators are as shown in Table 2.11.4 These data apply to reagent water only. It is the analysts responsibility to ensure the validity of this test method for watersof untested matrices.11.5 Precision and bias for this test method conforms to Practice D2777 77, which was in place at the time of