1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 975:2013Brown coals and lignites Determination of yield ofbenzene-soluble extract Semi-automatic methodBS ISO 975:2013 BRITISH STANDARDNational forewordThis British Standa
2、rd is the UK implementation of ISO 975:2013.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 ne
3、cessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 81214 9ICS 73.040Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was p
4、ublished under the authority of theStandards Policy and Strategy Committee on 31 May 2013.Amendments issued since publicationDate Text affectedBS ISO 975:2013 ISO 2013Brown coals and lignites Determination of yield of benzene-soluble extract Semi-automatic methodCharbons bruns et lignites Dterminati
5、on du rendement en extrait de benzne soluble Mthode semi-automatiqueINTERNATIONAL STANDARDISO975Fourth edition2013-05-01Reference numberISO 975:2013(E)BS ISO 975:2013ISO 975:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise specified, no
6、 part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including 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 membe
7、r body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 975:2013ISO 975:2013(E) ISO 2013 All rights reserved iiiContents PageForeword ivIntroduction v1
8、Scope . 12 Normative references 13 Principle 14 Reagent . 15 Apparatus . 16 Preliminary adjustment of instrument . 26.1 Adjustment of the extraction temperature . 26.2 Selection of periods of extraction, rinsing and evaporation 26.3 Procedure 27 Expression of results 38 Precision of the method 38.1
9、Repeatability limit 38.2 Reproducibility critical difference . 39 Test report . 4BS ISO 975:2013ISO 975:2013(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
10、 normally carried 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
11、 in the work. ISO 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 prep
12、are International 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 so
13、me of the elements 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 975 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee SC 5, Methods of analysis.This fourth edition cancels and
14、replaces the third edition (ISO 975:2000), of which this constututes a minor revision.iv ISO 2013 All rights reservedBS ISO 975:2013ISO 975:2013(E)IntroductionThe determination of yield of benzene-soluble extract is carried out using a semi-automatic instrument; a system combining extraction, rinsin
15、g and evaporation. As long as the sample is put in the extraction chamber of the instrument, the test can be done automatically. ISO 2013 All rights reserved vBS ISO 975:2013BS ISO 975:2013Brown coals and lignites Determination of yield of benzene-soluble extract Semi-automatic method1 ScopeThis Int
16、ernational Standard specifies a semi-automatic method for determination of the yield of benzene-soluble extract in 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 ap
17、plies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 5068-2, Brown coals and lignites Determination of moisture content Part 2: Indirect gravimetric method for moisture in the analysis sample3 PrincipleA test portion of the brown coal or
18、 lignite is extracted with benzene in a semi-automatic extraction instrument. The solvent is then removed by evaporation and the soluble residue dried to constant mass. The percentage of benzene-soluble extract is calculated from the mass of residue after drying and is reported on the dry basis.4 Re
19、agent4.1 Benzene, of analytical reagent grade, 20= 0,876 g/ml, distillation range 80 C to 81 C. At least 95 % shall distil within this range.WARNING Benzene is flammable and toxic by inhalation, ingestion or skin absorption. The test must be carried out in a hood and the benzene must be recovered as
20、 completely as possible.5 Apparatus5.1 Semi-automatic extraction instrument, containing mainly two units: the continuous extraction-evaporation device and the controller. The continuous extraction-evaporation device consists of a 100 ml conical flask, an extraction chamber and a condenser. The extra
21、ction chamber is 180 mm long and 30 mm in internal diameter and is provided with a water jacket through which the bath water is circulated in order to maintain the extraction temperature around the extraction chamber.5.2 Extraction thimble, 25 mm 80 mm. Cellulose or other thimbles are purchased or m
22、ade as follows.Cut filter paper into pieces of 75 mm 75 mm and 25 mm 25 mm. Moisten one large piece of the filter paper with distilled water and roll it snugly onto the external wall of a test tube of 25 mm diameter with a small hole pierced at the bottom. A small piece of filter paper is next moist
23、ened and rolled onto the bottom. Three large pieces and two small pieces are then rolled alternately onto the test tube. Remove the formed moist thimble by blowing at the mouth of the test tube and dry it in air or in an oven at 100 C.5.3 Air oven, capable of maintaining a temperature between 105 C
24、and 110 C, or vacuum oven, electrically heated, in which a temperature of 80 C 2 C and a pressure of about 50 kPa can be maintained.INTERNATIONAL STANDARD ISO 975:2013(E) ISO 2013 All rights reserved 1BS ISO 975:2013ISO 975:2013(E)5.4 Analytical balance, accurate to 0,1 mg.6 Preliminary adjustment o
25、f instrument6.1 Adjustment of the extraction temperaturePlace an extraction thimble with about 2 g of coal sample in the extraction chamber. Add 60 ml to 70 ml of benzene to the conical flask. Connect the flask to the extraction chamber. Switch on the electrical power and push down the programme but
26、ton. The extraction-evaporation device will then be automatically lowered until the flask is immersed in the water bath and the water bath starts heating. As the first drop of condensed benzene drips from the condenser, adjust the temperature of the water bath so that the dripping rate of benzene is
27、 about 4 ml/min to 5 ml/min and the sample is completely immersed in benzene in the thimble. Record the temperature and fix the position of the temperature controller. This temperature should be readjusted for changed ambient temperature.6.2 Selection of periods of extraction, rinsing and evaporatio
28、nIn general, the suitable periods of the above three steps are, respectively, 180 min, 10 min and 50 min. They can be readily adjusted with the corresponding timers. In the case of a high content of benzene-soluble constituents in the sample or excessively low barometric pressure, etc., readjustment
29、 of the extraction period may be necessitated in order to ensure the correct end-point of extraction, which is to be judged by the colourlessness of the last drops of extract solution.6.3 ProcedureWeigh, to the nearest 0,2 mg, about 2 g of general analysis test sample, transfer to the extraction thi
30、mble (5.2) and cover with a pad of absorbent cotton, which is fitted snugly on the wall of the thimble.Place the extraction thimble with sample in the extraction chamber (see 5.1).Add 60 ml to 70 ml of benzene to a previously dried and accurately weighed flask.Assemble the instrument.Switch on the e
31、lectrical power. Push down the programme button. The instrument will automatically perform the experiment in accordance with the following sequence:The extraction-evaporation device is lowered until the flask is immersed in the water bath as in the preliminary adjustment and the condenser is in an i
32、nclined position permitting refluxing. The heating of the water bath is started simultaneously.When the extraction temperature previously set is reached, the pump begins to circulate the hot water between the bath and the jacket of the extraction chamber. The benzene vapour from the flask passes thr
33、ough the extraction chamber and reaches the condenser, where it is condensed and drips onto the thimble. The extraction stage is thus in progress.After 180 min, or an otherwise set time, the pump stops and extraction is finished. Hot water flows back to the bath. The temperature of the extraction ch
34、amber drops to a temperature at which the benzene vapour can only reach the extraction chamber and condenses there. Thus a rinsing action is achieved, by means of which the benzene-soluble extract adhered to the wall is washed down into the flask by the condensed benzene. This is the rinsing stage.A
35、fter 10 min, rinsing is finished. The condenser is automatically changed to an inverted position permitting distillation. The pump works again so as to resume hot-water circulation. The benzene vapour condenses in the condenser and flows to the receiver. The stage of evaporation starts.After 50 min
36、of evaporation is finished, the extraction-evaporation system is elevated to the original position, permitting the flask to be detached from the extraction chamber. The programme is thus terminated.2 ISO 2013 All rights reservedBS ISO 975:2013ISO 975:2013(E)Detach the flask with soluble residue. Dry
37、 it in the air oven (5.3) maintained at 105 C to 110 C or in the vacuum oven (5.3) maintained at 80 C 2 C and about 50 kPa to constant mass.NOTE Constancy in mass is considered to have been achieved when the difference between successive dryings does not exceed 0,001 g.Carry out a moisture determina
38、tion on a separate test portion by the method specified in ISO 5068-2.7 Expression of resultsThe yield of benzene-soluble extract, wE,ad, in the general analysis test sample, expressed as a percentage by mass, is given by the formulawmmE,ad=12100wherem1is the mass, in grams, of benzene-soluble extra
39、ct;m2is the mass, in grams, of the test portion.The yield, expressed on the dry basis, is given by the formulawwwE,dME,ad=100100where wMis the mass fraction of moisture, in percent, of the general analysis test sample.The result (the mean of duplicate determinations, see 8.1) shall be reported on th
40、e dry basis to the nearest 0,1 %.8 Precision of the method8.1 Repeatability limitThe results of duplicate determinations, carried out at different times within a short interval, in the same laboratory, by the same operator, with the same apparatus, on two representative test portions taken from the
41、same analysis sample, should not differ by more than the values shown in Table 1.8.2 Reproducibility critical differenceThe means of the results of duplicate determinations, carried out in each of two different laboratories, on representative test portions taken from the same sample after the last s
42、tage of sample preparation, should not differ by more than the values shown in Table 1.Table 1Yield of benzene-soluble extract % (m/m)Repeatability limit (air-dried basis)Reproducibility critical difference (dry basis)less than 5 0,3 % absolute 0,5 % absolute5 to 10 inclusive 0,5 % absolute 0,7 % ab
43、solutemore than 10 5 % of the mean result 7 % of the mean result ISO 2013 All rights reserved 3BS ISO 975:2013ISO 975:2013(E)9 Test reportThe test report shall include the following information:a) a reference to this International Standard including year of publication;b) identification of the sampl
44、e tested;c) the results of the determination, together with the analysis basis;d) any unusual features noted during the determination.4 ISO 2013 All rights reservedBS ISO 975:2013BS ISO 975:2013ISO 975:2013(E) ISO 2013 All rights reservedICS 73.040Price based on 4 pagesThis page deliberately left bl
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