1、Designation: D1126 02 (Reapproved 2007)1D1126 12Standard 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 numbe
2、r 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 Department of Defense.1 NOTEAdded acronym to 3.1.2 and updated 11.5 editorially in August 200
3、7.1. Scope Scope*1.1 This test method covers the determination of hardness in water by titration. 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
4、/L as CaCO3; the upper limit can be extended to all concentrations by sample dilution. It is 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 ensur
5、e the validity of the test methodfor waters of untested matrices.1.3 The values stated in SI 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
6、 is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1066 Practice for Sampling SteamD1129 Terminology Relating to WaterD1193 Specifica
7、tion for Reagent WaterD2777 Practice for Determination 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. Terminology
8、3.1 DefinitionsFor definitions of terms used in this test method, refer to Terminology D1129.3.2 Definitions:Definitions of Terms Specific to This Standard:3.2.1 equivalent per million (epm), na unit chemical equivalent weight of solute per million unit weights of solution.3.2.2 laboratory control s
9、ample (LCS), na solution with certified hardness.3.1.3 For definitions of other terms used in this test method, refer to Terminology D1129.4. Summary of Test Method4.1 Calcium and magnesium ions in water are sequestered by the addition of disodium ethylenediamine tetraacetate. The endpoint of the re
10、action is detected by means of Chrome Black T3, which 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 Con
11、stituents in Water.Current edition approved Aug. 1, 2007March 1, 2012. Published August 2007March 2012. Originally approved in 1950. Last previous edition approved in 20022007 asD1126 02.D1126 02 (2007)1. DOI: 10.1520/D1126-02R07E01.10.1520/D1126-12.2 For referencedASTM standards, visit theASTM webs
12、ite, www.astm.org, or contactASTM Customer Service at 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 doc
13、ument is not an ASTM standard and is intended only to 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
14、 appropriate. In all cases only the current versionof 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. Unite
15、d States15. Significance and Use5.1 Hardness salts in 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 cation
16、s, but those other than Ca and Mg are seldom present 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 t
17、he calcium and magnesiumcontent.6. Interferences6.1 The 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. Reag
18、ents7.1 Purity of ReagentsReagent grade chemicals shall 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 ascer
19、tained that the reagent is of sufficiently high purity 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 C
20、hemical Society, see Annual Standards for Laboratory 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 InterferencesSubstanceMaximumConcentrationWithoutInterfe
21、rencein the TotalHardnessTest, mg/LMaximumConcentrationWithoutInterferencein 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
22、 + + 0.3 .Copper, Cu + + 20 2Iron, ferric, Fe + + 10B 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,
23、 Quebracho 200 50Tin, stannic, Sn + + 10 5Tin, stannous, 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 f
24、ew crystals ofK4Fe(CN)63H2O are added to the buffer immediately 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 1227.2 Purity of WaterUnless
25、 otherwise indicated, reference to water shall be understood 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
26、 and bias of the test method. Type II water was specified 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
27、 g of sodium tetraborate (Na2B4O710H2O) in 800 mL of 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
28、tetraacetate, having amagnesium-to-EDTA mole ratio of 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).
29、Diluteto 1 L with water.7.6 Calcium IndicatorUse powdered 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
30、 Black T3 in 50 mL of diethanolamine or triethanolamine. 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 powd
31、er has a storage life of at least 1 year.7.8 Hydrochloric 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 tetraacet
32、ate dihydrate in approximately 800 mL of water. Adjust 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). Adjus
33、t the concentration of the EDTA so that 1 mL willbe equivalent 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 Coll
34、ect the sample in accordance with Practice D1066 or Practices 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
35、HCl (7.8) solution. Add 0.5 mL of buffer(7.4) solution, 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 within
36、5 min after the buffer addition. If the titration requires 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
37、 employing a 100-mL sample, add twice the quantity of 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 calciu
38、m (7.6) indicator and stir.Addstandard Na2H2EDTA (7.9) 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 sa
39、mple and repeat the test.10. Calculations10.1 Calculate 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 123where:epm = equivalent parts per million; milliequivalents per liter,epm = e
40、quivalent parts per million; milliequivalents per litre,C = standard Na2H2EDTA solution added in titrating hardness, 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; milliequivale
41、nts per liter,epm = equivalent parts per million; milliequivalents per litre,D = standard Na2H2EDTA solution added in titrating calcium hardness, mL, andS = sample taken for test, mL.10.1.2 Calculate the magnesium hardness, epm, of the sample as follows:Magnesium hardness,epm5E2F (3)where:epm = equi
42、valent parts per million; milliequivalents per liter,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:Hardness,mg/Las CaCO351000 C1/S1 (4)where:C1 = standard Na2H2E
43、DTA 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 added in titrating calcium hardness, mL, andS1 = sample taken,
44、 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 operation and overall precision of the total hardness test
45、 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 50.0047 X10.40ST 50.0078 X11.80where:So = pooled single-operator precision, mg/L,St = overall precision, mg/L, andX = hardness concentr
46、ation, mg/L.11.2 The single operator and 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 X10.376 Supporting data have been filed
47、at ASTM International Headquarters and may be obtained by requesting Research Report RR:D19-1125. Contact ASTM CustomerService at serviceastm.org.D1126 124St 50.025 X10.61where:So = pooled single-operator precision, mg/LSt = overall precision, mg/L, andX = calcium hardness concentration, mg/L.11.3 R
48、ecoveries 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
49、 matrices.11.5 Precision and bias for this test method conforms to Practice D2777 77, which was in place at the time of collaborativetesting. Under the allowances made in 1.4 of D2777 06, 08, these precision and bias data do meet existing requirements forinterlaboratory studies of Committee D19 test methods.12. Quality Control (QC)12.1 The following quality control information is recommended for the determination of hardness in water.12.2 Acheck standard shall be analyzed at a minimum freque
