1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 5073:2013Brown coals and lignites Determination of humic acidsBS ISO 5073:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 5073:
2、2013.The UK participation in its preparation was entrusted to TechnicalCommittee PTI/16, Solid mineral fuels.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users
3、are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 81215 6ICS 73.040Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStan
4、dards Policy and Strategy Committee on 31 May 2013.Amendments issued since publicationDate Text affectedBS ISO 5073:2013 ISO 2013Brown coals and lignites Determination of humic acidsCharbons bruns et lignites Dosage des acides humiquesINTERNATIONAL STANDARDISO5073Third edition2013-05-01Reference num
5、berISO 5073:2013(E)BS ISO 5073:2013ISO 5073:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including
6、 photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749
7、09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 5073:2013ISO 5073:2013(E) ISO 2013 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 Principle 14.1 Total humic acids 14.2 Free humic acid 25 Reagents
8、26 Apparatus . 37 Sample . 38 Procedure. 38.1 Extraction of total humic acids 38.2 Extraction of free humic acid 38.3 Determination of humic acids in extracts 39 Expression of results 410 Precision of the method Repeatability limit 411 Test report . 5Annex A (normative) Determination of the ratio of
9、 carbon content of humic acids of brown coals and lignites . 6BS ISO 5073:2013ISO 5073:2013(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried
10、 out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO
11、 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International
12、 Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the element
13、s of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 5073 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee SC 5, Methods of analysis.This third edition cancels and replaces the seco
14、nd edition (ISO 5073:1999), of which this constitutes a minor revision.iv ISO 2013 All rights reservedBS ISO 5073:2013ISO 5073:2013(E)IntroductionIn this International Standard, humic acids are determined by the volumetric method with titration of extracts.The test is empirical and, in order to ensu
15、re producible results, it is essential that the composition of the extraction solution, the temperature and the time of extraction be carefully controlled. The value 0,59, which is the average ratio of carbon content of humic acids for many brown coals and lignites, has been proved to be applicable.
16、 Another value may also be used, predetermined as described in Annex A, and applicable to different countries or locations. ISO 2013 All rights reserved vBS ISO 5073:2013BS ISO 5073:2013Brown coals and lignites Determination of humic acids1 ScopeThis International Standard specifies volumetric metho
17、ds for the determination ofa) total humic acids, andb) free humic acid,of brown coals and lignites.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest
18、 edition of the referenced document (including any amendments) applies.ISO 1171, Solid mineral fuels Determination of ashISO 1213-2, Solid mineral fuels Vocabulary Part 2: Terms relating to sampling, testing and analysisISO 5068-2, Brown coals and lignites Determination of moisture content Part 2: I
19、ndirect gravimetric method for moisture in the analysis sampleISO 5069-2, Brown coals and lignites Principles of sampling Part 2: Sample preparation for determination of moisture content and for general analysis3 Terms and definitionsFor the purposes of this document, the terms and definitions given
20、 in ISO 1213-2 and the following apply.3.1humic acidsgroup of complex organic, amorphous compounds of high relative molecular mass which occur as free acid and as metal salts (humates)3.2total humic acidshumic acids extracted by an alkaline sodium pyrophosphate solution3.3free humic acidhumic acid e
21、xtracted by a sodium hydroxide solution4 Principle4.1 Total humic acidsExtraction of an analysis sample of coal is carried out with an alkaline sodium pyrophosphate solution. Carbon in the humic acid extracts is oxidized with potassium dichromate followed by titration of the excess dichromate with a
22、mmonium ferrous sulfate standard solution.INTERNATIONAL STANDARD ISO 5073:2013(E) ISO 2013 All rights reserved 1BS ISO 5073:2013ISO 5073:2013(E)4.2 Free humic acidExtraction of an analysis sample of coal is carried out with a sodium hydroxide solution. Carbon in the humic acid extracts is oxidized w
23、ith potassium dichromate followed by titration of the excess dichromate with ammonium ferrous sulfate standard solution.5 Reagents5.1 Sodium pyrophosphate, alkaline extraction solution.Dissolve 15 g of crystalline sodium pyrophosphate (Na4P2O710H2O) and 7 g of sodium hydroxide in 1 l of water.5.2 So
24、dium hydroxide solution.Dissolve 10 g of sodium hydroxide in 1 l of water.5.3 Potassium dichromate standard solution, c(1/6 K2Cr2O7) = 0,1 mol/l.Dissolve 4,903 6 g of potassium dichromate, previously dried at 130 C, in water. Transfer to a 1 l volumetric flask and dilute to the mark with water.5.4 P
25、otassium dichromate oxidizing solution, c(1/6 K2Cr2O7) = 0,4 mol/l.Dissolve 20 g of potassium dichromate in 1 l of water.5.5 Ammonium ferrous sulfate titration solution, c(NH4)2Fe(SO4)2 = 0,1mol/l.Dissolve 40 g of ammonium ferrous sulfate in 1 l of water. Add 20 ml of concentrated sulfuric acid. Sto
26、re in a dark bottle.Standardize the ammonium ferrous sulfate titration solution against the c(1/6 K2Cr2O7) = 0,1 mol/l potassium dichromate standard solution (5.3) for each batch of samples to be analysed.Pipette 25 ml of potassium dichromate standard solution (5.3) into a 300 ml conical flask. Add
27、70 ml to 80 ml of water. Carefully add 10 ml of concentrated sulfuric acid and 3 drops of 1,10-phenantholine indicator. After cooling, titrate with the ammonium ferrous sulfate standard solution to a red colour.Calculate the concentration, in moles per litre, of the ammonium ferrous sulfate solution
28、 as follows:c = 0,1 25/V wherec is the concentration, expressed in moles per litre, of the ammonium ferrous sulfate solution;V is the volume of ammonium ferrous sulfate solution required for the titration.5.6 1,10-Phenanthroline indicator.Dissolve 1,5 g of 1,10-phenanthroline and 1 g of ammonium fer
29、rous sulfate in 100 ml of water. Store in a dark bottle.5.7 Sulfuric acid, concentrated, 20= 1,84 g/ml.2 ISO 2013 All rights reservedBS ISO 5073:2013ISO 5073:2013(E)6 Apparatus6.1 Water bath, thermostatically controlled to (100 1) C, with four holes at least.6.2 Balance, sensitive to 0,1 mg.7 Sample
30、Prepare the sample for the determination of humic acids in accordance with ISO 5069-2.For calculation to a dry basis, the moisture in the analysis sample shall be determined according to ISO 5068-2.8 Procedure8.1 Extraction of total humic acidsWeigh (0,2 0,000 2) g of analysis sample into a conical
31、flask. Add 150 ml of alkaline sodium pyrophosphate extraction solution (5.1) and mix until the sample is thoroughly wetted. Place a small funnel on the flask and heat in the boiling water bath (6.1) for 2 h, shaking frequently to ensure precipitation of insoluble material.Remove the flask from the w
32、ater bath. Allow to cool to room temperature and quantitatively transfer the extract and residue to a 200 ml volumetric flask. Dilute to the mark with water and shake to ensure thorough mixing.Determine the total humic acids (wHA,t) extracted by alkaline sodium pyrophosphate as specified in 8.3.8.2
33、Extraction of free humic acidWeigh (0,2 0,000 2) g of analysis sample into a conical flask. Add 150 ml of sodium hydroxide extraction solution (5.2) and mix until the sample is thoroughly wetted. Place a small funnel on the flask and heat in the boiling water bath (6.1) for 2 h, shaking frequently t
34、o ensure thorough mixing.Remove the flask from the water bath. Allow to cool to room temperature and quantitatively transfer the extract and residue to a 200 ml volumetric flask using water. Dilute to the mark with water and shake to ensure thorough mixing.Determine the free humic acid (wHA,f) extra
35、cted by sodium hydroxide as specified in 8.3.8.3 Determination of humic acids in extracts8.3.1 Oxidation of extractsPipette 5 ml of clarified or dry-filtered extract into a 250 ml to 300 ml conical flask. Pipette 5 ml of potassium dichromate oxidizing solution (5.4) into the flask. Carefully add 15
36、ml of concentrated sulfuric acid (5.7). Place in the boiling water bath (6.1) and heat for 30 min. Allow to cool to room temperature. Dilute to approximately 100 ml.8.3.2 Titration of extractsAdd 3 drops of 1,10-phenanthroline indicator (5.6) to the solution from 8.3.1 and titrate with the ammonium
37、ferrous sulfate titration solution (5.5) to a brick red colour. ISO 2013 All rights reserved 3BS ISO 5073:2013ISO 5073:2013(E)8.3.3 Blank8.3.3.1 Blank for total humic acidsPipette 5 ml of sodium pyrophosphate (5.1) into a 250 ml to 300 ml conical flask, add the potassium dichromate oxidizing solutio
38、n (5.4) and the concentrated sulfuric acid as specified in 8.3.1 and carry out the titration as specified in 8.3.2.8.3.3.2 Blank for free humic acidsPipette 5 ml of sodium hydroxide (5.2) into a 250 ml to 300 ml conical flask, add the potassium dichromate oxidizing solution and the concentrated sulf
39、uric acid as specified in 8.3.1 and carry out the titration as specified in 8.3.2.9 Expression of resultsCalculate the total humic acid content (wHA,t) or free humic acid content (wHA,f), as a percentage by mass, of the sample as analysed according to the following formula:wVV cmVVHAea= (),010 00305
40、9100 where0,003 is the millimole mass of carbon, in grams per millimole;V0is the volume of the ammonium ferrous sulfate titration solution used in the blank titre, in millilitres;V1is the volume of the ammonium ferrous sulfate titration solution used in the extract titre, in millilitres;c is the con
41、centration of the ammonium ferrous sulfate titration solution as determined in 5.5, in moles per litre;Veis the volume of the extract, in millilitres;Vais the volume of the aliquot taken for titration, in millilitres;0,59 is the average ratio of carbon content of humic acids for brown coals and lign
42、ites (see the note below);m is the mass of the sample taken for the test, in grams.NOTE For different countries or locations, the average ratio of carbon content of humic acids of brown coals and lignites can be checked or redetermined as specified in Annex A.10 Precision of the method Repeatability
43、 limitThe results of duplicate determinations, carried out on the same day in the same laboratory by the same operator with the same apparatus on the two separate test portions of the same sample, should not differ by more than the values given in Table 1.4 ISO 2013 All rights reservedBS ISO 5073:20
44、13ISO 5073:2013(E)Table 1 PrecisionHumic acid content Repeatability limitUp to 20 % 1 % (absolute)Above 20 % 2 % (absolute)11 Test reportThe test report shall contain the following information:a) a reference to this International Standard including year of publication;b) the identification of the sa
45、mple tested;c) the result of the determination performed, together with the analysis basis;d) any unusual feature noted during the determination. ISO 2013 All rights reserved 5BS ISO 5073:2013ISO 5073:2013(E)Annex A (normative) Determination of the ratio of carbon content of humic acids of brown coa
46、ls and lignitesA.1 Weigh about 10 g of analysis sample of brown coals and lignites into three or four conical flasks separately depending on the humic acid content of the sample (can yield 3 g or 4 g of humic acid sample). Pipette an appropriate amount of the alkaline sodium pyrophosphate extraction
47、 (5.1) into each conical flask equivalent to 150 ml per gram of the analysis sample and mix until the sample is thoroughly wetted. Place a small funnel on the flask and heat in the boiling water bath (6.1) for 2 h, shaking frequently to ensure precipitation of insoluble material.A.2 Remove the flask
48、 from the water bath, cool to room temperature, centrifuge the contents of flasks for 5 min. Collect the solution in the beakers. Add (1 + 1) HCl to the solution until the humic acid is precipitated fully (pH 1 to pH 3 for the solution).A.3 Centrifuge the suspension. Decant and discard the solution.
49、 Separate the residue through a medium-textured paper, wash the residue with water until peptization of the humic acids begins, which is indicated by the formation of a gel or colloid (pH 6 to pH 7 for the filtered solution).A.4 Transfer the residue to the clear beakers or vessels and dry it at 105 C to 110 C. The dried residue is the humic acid sample.A.5 Weigh 1 g, to the nearest 0,2 mg, of the humic acid sample (A.4) into a clear, dry dish and determine the ash according to ISO 1171. Calculate the humic
