1、Designation: D2973 10Standard Test Method forTotal Nitrogen in Peat Materials1This standard is issued under the fixed designation D2973; 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 parenth
2、eses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers a chemical test method2for thedetermination of the weight percent of nitrogen in peatmaterial.1.2 The values stated in SI units
3、 are to be regarded asstandard. No other units of measurement are included in thisstandard.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 practi
4、ces and determine the applica-bility of regulatory limitations prior to use. (See PracticeD3740)2. Referenced Documents2.1 ASTM Standards:3D653 Terminology Relating to Soil, Rock, and ContainedFluidsD1193 Specification for Reagent WaterD2974 Test Methods for Moisture,Ash, and Organic Matterof Peat a
5、nd Other Organic SoilsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4753 Guide for Evaluating, Selecting, and SpecifyingBalances and Standard Masses for Use in Soil, Rock, andConstruction Materi
6、als TestingD6026 Practice for Using Significant Digits in GeotechnicalDataE145 Specification for Gravity-Convection and Forced-Ventilation Ovens3. Terminology3.1 Definitions:3.1.1 For common definitions of terms in this standard, referto Terminology D653.4. Summary of Test Method4.1 In this procedur
7、e, the nitrogen is converted into ammo-nium salts by destructive digestion of the sample with a hot,catalyzed mixture of concentrated sulfuric acid and potassiumsulfate. These salts are subsequently decomposed in a hotalkaline solution from which the ammonia is recovered bydistillation and finally d
8、etermined by acidimetric titration.5. Significance and Use5.1 Nitrogen content is important as it is one of the primaryplant food elements necessary for plant growth. Nitrogen ispresent in peat as organic nitrogen, and therefore, does notrelease nitrogen to plants as quickly as chemical fertilizers.
9、However, nitrogen from peat continues to be released forseveral years as the organic matter decomposes.6. Apparatus6.1 For DigestionUse Kjeldahl flasks of hard, moderatelythick, well-annealed glass with total capacity of about 800 mL.Conduct digestion over a heating device adjusted to bring 250mL of
10、 water at 25C to a rolling boil in about 5 min.6.2 For DistillationUse 800-mL Kjeldahl flasks fittedwith rubber stoppers through which passes the lower end of anefficient scrubber bulk or trap to prevent mechanical carry-overof sodium hydroxide solution during distillation. Connect theupper end of t
11、he bulb tube to the condenser tube by rubbertubing. Trap the outlet of the condenser in such a way as toensure complete absorption of ammonia distilled over into theacid in the receiver.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility
12、of Subcommittee D18.06 on Physical-ChemicalInteractions of Soil and Rock.Current edition approved Oct. 1, 2010. Published November 2010. Originallyapproved in 1971. Last previous edition approved in 2004 as D297371(2004).Withdrawn in 2009 and reinstated in 2010 as D297310. DOI: 10.1520/D2973-10.2Thi
13、s method is currently undergoing an extensive review by ASTM CommitteeD18 and additional alternative methods will be proposed.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information,
14、 refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 Erlenmeyer Flask, 250 or 300-mL capacity.7. Reagen
15、ts7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades m
16、ay beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination. All water used for this testmethod shall be ASTM Type III or better as defined inSpecification D1193.7.2 Boric Acid Solution, 4 % (40 g/L)D
17、issolve 40 g ofboric acid (H3BO3) in water and dilute to 1 L.7.3 Mercuric Oxide Tablets (HgO).7.4 Mixed IndicatorDissolve 200 mg of methyl red in 100mL of alcohol. Dissolve 200 mg methylene blue in 100 mL ofalcohol. Mix in a ratio of 1 part methyl red to 2 parts methyleneblue.7.5 Potassium Sulfate (
18、K2SO4).7.6 Potassium Sulfide Solution (40 g/L)Dissolve 40 g ofpotassium sulfide in water and dilute to 1 L.7.7 Sodium Hydroxide Solution (450 g/L)Dissolve 450 gof nitrate-free sodium hydroxide (NaOH) in water and dilute to1 L. The specific gravity of the solution should be 1.36 orgreater.7.8 Sulfuri
19、c Acid (sp gr 1.84)Concentrated sulfuric acid(H2SO4).7.9 Sulfuric Acid, Standard (0.1 to 0.3 N)Dissolve 3.0 to9.0 mL of sulfuric acid (H2SO4) in water and dilute to 1 L.7.10 Zinc, 30 mesh.8. Preparation of Sample8.1 Air-dry the sample in accordance with Method II of TestMethods D2974. Record the per
20、centage of moisture removedby air-drying. (See Specification E145)9. Procedure9.1 Mix thoroughly the air-dried, ground sample and weighto the nearest 1 mg the equivalent of 10.0 g of test specimen onthe as-received basis. (See Guide D4753) Determine the gramsof air-dried sample equivalent to 10.0 g
21、of as-received sampleas follows:equivalent sample weight, g 5 (1)10.0 10.0 3 percent moisture removed!/1009.2 Place the weighed sample in the digestion flask, add 0.7g of HgO, 15 g of powdered K2SO4, and 35 mL of H2SO4.Place the flask in an inclined position and heat gradually. Thenboil briskly unti
22、l the solution clears. Continue boiling for anadditional 30 min. Cool, add about 300 mL of water, coolbelow 25C, add 25 mL of K2S solution and mix to precipitatethe mercury. Add a pinch of zinc to prevent bumping, tilt theflask, and add a layer of NaOH solution sufficient to make thecontents strongl
23、y alkaline. Do not agitate the mixture. Imme-diately connect the flask to the digestion bulb or condenser.Have the tip of the condenser immersed in the H3BO3solution(this need not be measured) in the receiver and then rotate theflask to mix the contents thoroughly. Heat until the ammoniahas distille
24、d (at least 150 mLof distillate). Titrate with standardacid using mixed indicator to violet end point.10. Calculation10.1 Calculate the percentage nitrogen as follows:Nitrogen asreceived!,%5 A 3 B! 3 0.14 (2)where:A = millilitres of 0.1 to 0.3 N H2SO4required for titrationof the solution, andB = nor
25、mality of the H2SO4.11. Report11.1 Report to the nearest 0.1 % the nitrogen content of theas-received sample. (See Practice D6026)12. Precision and Bias12.1 PrecisionDue to the nature of the soil or rockmaterials tested by this method, it is either not feasible or toocostly at this time to produce m
26、ultiple specimens that haveuniform physical properties.Any variation observed in the datais just as likely to be due to specimen variation as to operatoror laboratory testing variation. Subcommittee D18.18 wel-comes proposals that would allow for development of a validprecision statement.12.2 BiasTh
27、ere is no accepted reference value for this testmethod, therefore, bias cannot be determined.13. Keywords13.1 chemical analysis; nitrogen compounds; peat4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents
28、notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D2973 102SUMMARY OF CHANGESCommittee D18 has identified the loca
29、tion of selected changes to this test method since the last issue,D297371(2004), that may impact the use of this test method. (Approved October 1, 2010)(1) Revised the Referenced Documents Section. Added a newTerminology Section and renumbered subsequent sections.(2) Added reference to ASTM Type III
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33、Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D2973 103
