1、INTERNATIONAL STANDARD ISO 5931 First edition 2000-08-15 Reference number ISO 5931:2000(E) ISO 2000 Carbonaceous materials used in the production of aluminium Calcined coke and calcined carbon products Determination of total sulfur by the Eschka method Produits carbons utiliss pour la production de
2、laluminium Coke calcin et produits carbons calcins Dosage du soufre total par la mthode EschkaISO 5931:2000(E) ii ISO 2000 All rights reserved PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be
3、edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this file, parties accept therein the responsibility of not infringing Adobes licensing policy. The ISO Central Secretariat accepts no liability in this area. Adobe is
4、a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member
5、 bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. ISO 2000 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, elec- tronic or me
6、chanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs mem- ber 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.ch Web www
7、.iso.ch Printed in SwitzerlandISO 5931:2000(E) ISO 2000 All rights reserved iii Contents Page 1 Scope . 1 2 Normative references . 1 3 Principle 1 4 Reagents 1 5 Apparatus . 2 6 Preparation of test sample 2 7 Procedure . 3 8 Expression of results 4 9 Precision . 5 10 Test report 5 Annex A Derivation
8、 of factors used in the calculation in clause 8 . 6 Bibliography. 7ISO 5931:2000(E) iv ISO 2000 All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standa
9、rds is normally carried out through ISO technical com- mittees. 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 liai- son with ISO, also
10、 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 Directives, Part 3. Draft International Standards adopte
11、d 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 elements of this International Standard may be the sub
12、ject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 5931 was prepared by Technical Committee ISO/TC 47, Chemistry, Subcommittee SC 7, Aluminium oxide, cryolite, aluminium fluoride, sodium fluoride, carbonaceous products f
13、or the aluminium industry. Annex A of this International Standard is for information only.ISO 5931:2000(E) ISO 2000 All rights reserved v Introduction Instrumental methods for a more rapid determination of total sulfur are now available. lf such a method is to be used, it is important to demonstrate
14、 that the method is free from bias when compared to this reference method and will give levels of repeatability and reproducibility which are the same as, or better than, those quoted for this reference method (see clause 9).INTERNATIONAL STANDARD ISO 5931:2000(E) ISO 2000 All rights reserved 1 Carb
15、onaceous materials used in the production of aluminium Calcined coke and calcined carbon products Determination of total sulfur by the Eschka method 1 Scope This International Standard specifies a reference method for determining the total sulfur content of calcined coke and calcined carbon products
16、 by the Eschka method, provided that they contain a minimum of by mass and prefer- ably less than by mass of sulfur. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated refe
17、rences, subsequent amendments to, or revisions of, any of these publica- tions do not apply. However, parties to agreements based on this International Standard are encouraged to investi- gate the possibility of applying the most recent editions of the normative documents indicated below. For undate
18、d references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 4787:1984, Laboratory glassware Volumetric glassware Methods for use and testing of capacity. ISO 4788:1980, Laboratory glassware
19、Graduated measuring cylinders. ISO 5069-2:1983, Brown coals and lignites Principles of sampling Part 2: Sample preparation for determination of moisture content and for general analysis. ISO 6375:1980, Carbonaceous materials for the production of aluminium Coke for electrodes Sampling. 3 Principle A
20、 test portion is ignited in intimate contact with Eschka mixture in an oxidizing atmosphere to remove combustible matter and to convert the sulfur to sulfate. The sulfate is then extracted using a hydrochloric acid solution and the sul- fur content, in the form of sulfate, is determined gravimetrica
21、lly by precipitation of the sulfate with barium chloride. 4R e a g e n t s WARNING Care should be exercised when handling the reagents, many of which are toxic and corrosive. During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only distilled water or wa
22、ter of equivalent purity. 4.1 Eschka mixture. Mix two parts by mass of light, calicined magnesium oxide with one part by mass of anhydrous sodium (or potas- sium) carbonate. Pass the mixture entirely through a test sieve of nominal size of openings. 4.2 Hydrochloric acid, concentrated, approximately
23、 , approximately by mass. 0,1 % 4% 212 m 1,18 g/ml 36 %ISO 5931:2000(E) 2 ISO 2000 All rights reserved 4.3 Potassium sulfate, solution. Weigh, to the nearest , about of potassium sulfate, previously dried at a temperature of to . D i sso lv ei nw at e ra ndd il ut eto . 4.4 Barium chloride, approxim
24、ately solution. Dissolve of barium chloride dihydrate in water and dilute to . Filter before use through a close-textured, dou- bly acid-washed filter-paper or filter-paper pad (see 5.8). 4.5 Methyl red, indicator solution. Dissolve of 2-(4-dimethylaminophenylazo) benzoic acid, sodium salt (methyl r
25、ed) in of water. 4.6 Ammonia, concentrated solution, no less than by mass. 4.7 Silver nitrate, solution. Dissolve of silver nitrate in water and dilute to . Store in a dark glass bottle. 5 Apparatus 5.1 Analytical balance, capable of weighing to the nearest . 5.2 Graduated glassware, complying with
26、the requirements for class A in ISO 4788 and in accordance with ISO 4787. 5.3 Electrically heated muffle furnace, capable of being maintained at . The ventilation through the muffle furnace shall be such as to give about five air changes per minute. 5.4 Crucible, of platinum, silica or glazed porcel
27、ain, of approximately capacity. 5.5 Flat plate, thick, of silica (or other suitable refractory material), which fits easily into the muffle furnace (5.3). 5.6 Gooch crucible, with a maximum pore size of , of glazed porcelain or sintered glass. Before commencing the filtration, dry the Gooch crucible
28、 and pad for in the air oven (5.7) at and weigh it to the nearest . 5.7 Air oven, capable of being maintained at . 5.8 Filter paper or filter-paper pad, doubly acid-washed, ashless, close-textured and/or medium-textured. To prepare the filter-paper pad, shake doubly acid-washed filter-paper clipping
29、s (cut into pieces of approximately ) with water in a bottle until the paper is thoroughly disintegrated. Place a porcelain filter cone of in a funnel. Close the stem of the funnel with a finger and add water until the cone is immersed and the funnel stem is full. Shake sufficient paper pulp to form
30、 a pad thick onto the cone and level it with a flat-ended glass rod. Allow the excess water to drain off by removing the finger from the stem and as drainage ceases, lightly tamp the pad around the edges with the glass rod. Finally wash with water to render the filter ready for use. 5.9 Dessicator.
31、0,1 mg 2 g 105 C1 1 0 C 1l 85 g/l 100 g 1 l 1g 1l 25 % 17 g/l 17 g 1 l 0,1 mg (800 25) C 25 ml 6mm 7 m 1h (130 10) C 0,1 mg (130 10) C 1cm 2 25 mm 75 mm 5mmISO 5931:2000(E) ISO 2000 All rights reserved 3 6 Preparation of test sample The test sample is the representative sample prepared in accordance
32、 with ISO 6375. Expose the test sample, dis- tributed in a thin layer, to the laboratory atmosphere for the minimum time required for the moisture content to reach approximate equilibrium. Before commencing the determination, thoroughly mix the test sample for at least , preferably by mechanical mea
33、ns. lf the results are to be calculated other than on an “air-dried” basis (see clause 8), then, after weighing the test por- tion (see 7.1), determine the moisture content using another portion of the test sample. 7 Procedure 7.1 Test portion Take two test portions of , each weighed to the nearest
34、. Carry out the procedure given in 7.2 to 7.6 on each test portion. 7.2 Loading the crucible Weigh of the Eschka mixture (4.1). Divide this mixture into three portions, , and , and weigh each to the nearest . For this purpose, it may be convenient to calibrate two glass tubes for the and por- tions.
35、 Uniformly cover the bottom of the crucible with the portion of the Eschka mixture. In another suitable vessel, mix the test portion thoroughly with the portion of the Eschka mixture. Transfer this mixture to the crucible. Level the contents by tapping the crucible gently on the laboratory benchtop
36、and cover the contents uniformly with portion of the Eschka mixture. NOTE The layer of Eschka mixture below the test portion mixture reduces attack on the porcelain surface, so that the extraction of sulfate with hot water is complete even when the surface deteriorates. 7.3 Ignition Place the loaded
37、 crucible (or crucibles) on the cold insulating plate (5.5) and insert into the muffle furnace (5.3) main- tained at , and heat for at least . Withdraw the crucible (or crucibles) and allow to cool. NOTE The cracking of porcelain crucibles can be prevented, if they are slowly cooled by insertion int
38、o supports of light porous firebrick upon removal from the muffle furnace. 7.4 Recovering the residue Transfer the ignited mixture from the crucible to a beaker containing to of water. lf unburnt parti- cles are present, stop the determination and repeat the test. Wash the crucible thoroughly with a
39、bout of hot water, then add the washings to the contents of the beaker. 7.5 Extraction Place a watch-glass on the beaker and, tilting the watch-glass to leave an opening, carefully add enough hydrochloric acid (4.2) to dissolve the solid matter ( will normally be required) while warming the contents
40、 of the beaker to enhance solution. Boil for to expel carbon dioxide. Filter (5.8) and collect the filtrate in a conical beaker. NOTE A medium-textured, doubly acid-washed filter-paper or a filter-paper pad can be used to speed filtration. 1 min 1 g 0,1 mg 4 g 0,5 g 1,0 g 2,5 g 0,1 mg 0,5 g 1,0 g 0,
41、5 g 2,5 g 25 ml 1,0 g 800 C 3h 400 ml 25 ml 30 ml 50 ml 17 ml 5 min 400 mlISO 5931:2000(E) 4 ISO 2000 All rights reserved Wash the filter with five portions of hot water. Add 2 or 3 drops of the methyl red indicator solution (4.5) to the combined filtrate and washings, and then cautiously add the am
42、monia solution (4.6) until the colour of the indicator changes and a trace of precipitate is formed. Add just enough hydrochloric acid (4.2) to redissolve the precipitate and then add in excess. 7.6 Precipitation of barium sulfate After extraction, dilute the solution, if necessary, to approximately
43、 and cover the beaker containing the solution with a watch-glass. Heat the covered beaker until the solution boils then reduce the heat slightly until the solution ceases to boil. Using a pipette, add, over a period of , of the cold barium sulfate solution to the middle of the hot, stirred solution.
44、 Keep the solution just below the boiling point for . Filter the solution using one of the following techniques: a) by gravity through an ashless, close-textured, doubly acid-washed filter-paper (see 5.8) of diameter to . Carefully fold the filter-paper and fit it into a fluted, long-stemmed funnel,
45、 so that the stem remains full of liquid during the filtration; b) by gravity through a filter-paper pad prepared from ashless, doubly acid-washed filter-paper (see 5.8); c) by suction through a pad of filtration mineral fibre in a Gooch crucible (5.6). Wash the precipitate with hot water, using no
46、more than , until the last of the washings give no more than a faint opalescence with the silver nitrate solution (4.7). lf technique a) or b) is used, place the wet filter-paper or pad in the previously ignited and weighed crucible (5.4) on the cold flat plate (5.5). If technique b) is used, after
47、transferring the filter-paper pad to the crucible, wipe the funnel successively with two halves of an ashless filter-paper and place this paper in the crucible with the pad. Insert the crucible slowly into the muffle furnace (5.3) maintained at , and heat for . Cool in a desiccator (5.9) and reweigh
48、 to the nearest . lf technique c) is used, dry the Gooch crucible (5.6) and pad for 1 h in the air oven (5.7) at , cool in a desicca- tor (5.9) and reweigh to the nearest . 7.7 Blank Carry out a blank determination using the same procedure specified in 7.2 to 7.6, but omitting the test portion . In
49、7.5, using a one-mark pipette, add of the potassium sulfate solution (4.3) to the filtrate before adding the methyl red indicator solution (4.5). 8 Expression of results The sulfur content, , of the sample, expressed as a percentage by mass, is given by the equation where is the mass, expressed in grams, of the test portion; is the mass, expressed in grams, of barium sulfate found in the determination; is the mass, expressed in grams, of barium sulfate found in the control; 20 ml 1ml 200 ml 20 s 10 m
