1、raising standards worldwide NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI Standards Publication BS ISO 975:2013 Brown coals and lignites Determination of yield of benzene-soluble extract Semi-automatic methodBS ISO 975:2013 BRITISH STANDARD National foreword This British
2、 Standard is the UK implementation of ISO 975:2013. The UK participation in its preparation was entrusted to Technical Committee PTI/16, Solid mineral fuels. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to includ
3、e all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2013. Published by BSI Standards Limited 2013 ISBN 978 0 580 81214 9 ICS 73.040 Compliance with a British Standard cannot confer immunity from legal obligations. This Br
4、itish Standard was published under the authority of the Standards Policy and Strategy Committee on 31 May 2013. Amendments issued since publication Date Text affectedBS ISO 975:2013 ISO 2013 Brown coals and lignites Determination of yield of benzene- soluble extract Semi-automatic method Charbons br
5、uns et lignites Dtermination du rendement en extrait de benzne soluble Mthode semi-automatique INTERNATIONAL STANDARD ISO 975 Fourth edition 2013-05-01 Reference number ISO 975:2013(E)BS ISO 975:2013ISO 975:2013(E)ii ISO 2013 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2013 All rights reser
6、ved. 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 photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
7、 at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandBS ISO 975:2013ISO 975:2013(E) ISO 2013 All rights reserved i
8、ii Contents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 Principle 1 4 Reagent . 1 5 Apparatus . 1 6 Preliminary adjustment of instrument . 2 6.1 Adjustment of the extraction temperature . 2 6.2 Selection of periods of extraction, rinsing and evaporation 2 6.3 Procedure 2 7
9、 Expression of results 3 8 Precision of the method 3 8.1 Repeatability limit 3 8.2 Reproducibility critical difference . 3 9 Test report . 4BS ISO 975:2013ISO 975:2013(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO mem
10、ber bodies). The work of preparing International Standards is 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, governmen
11、tal and non-governmental, in liaison with ISO, also take part 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 Direc
12、tives, Part 2. The main task of technical committees is to prepare 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 bodi
13、es casting a vote. Attention is drawn to the possibility that some 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, Subcom
14、mittee SC 5, Methods of analysis. This fourth edition cancels and 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) Introduction The determination of yield of benzene-soluble extract is carried out usin
15、g a semi-automatic instrument; a system combining extraction, rinsing 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 y
16、ield of benzene-soluble extract Semi-automatic method 1 Scope This International Standard specifies a semi-automatic method for determination of the yield of benzene- soluble extract in brown coals and lignites. 2 Normative references The following referenced documents are indispensable for the appl
17、ication of this document. For dated references, only the edition cited applies. 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 moi
18、sture in the analysis sample 3 Principle A test portion of the brown coal or 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
19、 from the mass of residue after drying and is reported on the dry basis. 4 Reagent 4.1 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 absorpti
20、on. The test must be carried out in a hood and the benzene must be recovered as completely as possible. 5 Apparatus 5.1 Semi-automatic extraction instrument, containing mainly two units: the continuous extraction- evaporation device and the controller. The continuous extraction-evaporation device co
21、nsists of a 100 ml conical flask, an extraction chamber and a condenser. The extraction 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.
22、5.2 Extraction thimble, 25 mm 80 mm. Cellulose or other thimbles are purchased or made 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
23、with a small hole pierced at the bottom. A small piece of filter paper is next moistened 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 i
24、n an oven at 100 C. 5.3 Air oven, capable of maintaining a temperature between 105 C 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 ST ANDARD ISO 975:2013(E) ISO 2013 All rights reserved 1BS ISO 975:2
25、013ISO 975:2013(E) 5.4 Analytical balance, accurate to 0,1 mg. 6 Preliminary adjustment of instrument 6.1 Adjustment of the extraction temperature Place 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 flas
26、k to the extraction chamber. Switch on the electrical power and push down the programme button. 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
27、condenser, adjust the temperature of the water bath so that the dripping rate of benzene is 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
28、 changed ambient temperature. 6.2 Selection of periods of extraction, rinsing and evaporation In 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-
29、 soluble constituents in the sample or excessively low barometric pressure, etc., readjustment 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 Procedure Weigh,
30、to the nearest 0,2 mg, about 2 g of general analysis test sample, transfer to the extraction thimble (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
31、benzene to a previously dried and accurately weighed flask. Assemble the instrument. Switch on the electrical 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
32、the flask is immersed in the water bath as in the preliminary adjustment and the condenser is in an inclined 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 b
33、etween the bath and the jacket of the extraction chamber. The benzene vapour from the flask passes through 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 s
34、tops and extraction is finished. Hot water flows back to the bath. The temperature of the extraction chamber 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
35、adhered to the wall is washed down into the flask by the condensed benzene. This is the rinsing stage. After 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 va
36、pour condenses in the condenser and flows to the receiver. The stage of evaporation starts. After 50 min 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 terminat
37、ed.2 ISO 2013 All rights reservedBS ISO 975:2013ISO 975:2013(E) Detach the flask with soluble residue. Dry 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 ach
38、ieved when the difference between successive dryings does not exceed 0,001 g. Carry out a moisture determination on a separate test portion by the method specified in ISO 5068-2. 7 Expression of results The yield of benzene-soluble extract, w E,ad , in the general analysis test sample, expressed as
39、a percentage by mass, is given by the formula where m 1 is the mass, in grams, of benzene-soluble extract; m 2 is the mass, in grams, of the test portion. The yield, expressed on the dry basis, is given by the formula w w w where w Mis the mass fraction of moisture, in percent, of the general analys
40、is test sample. The result (the mean of duplicate determinations, see 8.1) shall be reported on the dry basis to the nearest 0,1 %. 8 Precision of the method 8.1 Repeatability limit The results of duplicate determinations, carried out at different times within a short interval, in the same laborator
41、y, by the same operator, with the same apparatus, on two representative test portions taken from the same analysis sample, should not differ by more than the values shown in Table 1. 8.2 Reproducibility critical difference The means of the results of duplicate determinations, carried out in each of
42、two different laboratories, on representative test portions taken from the same sample after the last stage of sample preparation, should not differ by more than the values shown in Table 1. Table 1 Yield of benzene-soluble extract % (m/m) Repeatability limit (air-dried basis) Reproducibility critic
43、al difference (dry basis) less than 5 0,3 % absolute 0,5 % absolute 5 to 10 inclusive 0,5 % absolute 0,7 % absolute more 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 report The test report shall include the following inform
44、ation: a) a reference to this International Standard including year of publication; b) identification of the sample 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 IS
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