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© ISO 2017 Iron ores — Determination of sulfur content — Part 2 Combustion/titration method Minerais de fer — Dosage du soufre — Partie 2 Méthode par combustion et titration INTERNATIONAL STANDARD ISO[.]
INTERNATIONAL STANDARD ISO 4689-2 Third edition 2017-03 Iron ores — Determination of sulfur content — Part 2: Combustion/titration method Minerais de fer — Dosage du soufre — Partie 2: Méthode par combustion et titration Reference number ISO 4689-2:2017(E) © ISO 2017 ISO 4689-2 : 01 7(E) COPYRIGHT PROTECTED DOCUMENT © ISO 2017, Published in Switzerland All rights reserved Unless otherwise specified, no part o f 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 ISO’s member body in the country o f the requester ISO copyright o ffice Ch de Blandonnet • CP 401 CH-1214 Vernier, Geneva, Switzerland Tel +41 22 749 01 11 Fax +41 22 749 09 47 copyright@iso.org www.iso.org ii © ISO 2017 – All rights reserved ISO 4689-2 : 01 7(E) Page Contents iv Introduction v Scope Normative references Terms and definitions Principle Reagents Apparatus Sampling and samples 7.2 Preparation of predried test samples Procedure 8.1 Number of determinations 8.2 Test portion 8.3 Blank test and check test 8.4 Determination Expression of results 9.1 Calculation of sulfur content 9.2 General treatment of results f 9.2.3 Between-laboratories precision 9.2.4 Check for trueness f 10 Test report Foreword 7.1 Annex A Lab o rato ry s amp le 9.2 Rep eatab ility and p ermis s ib le to lerance 9.2 D eterminatio n o 9.2 C alculatio n o (normative) analytical res ult final res ult Flowsheet of the procedure for the acceptance of analytical values for 1 Annex B (informative) Derivation of repeatability and permissible tolerance equations Annex C (informative) Precision data obtained by international analytical trial Bibliography test samples © ISO 2017 – All rights reserved iii ISO 4689-2 : 01 7(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies) The work o f 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, governmental 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 o f electrotechnical standardization The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part In particular the different approval criteria needed for the di fferent types o f ISO documents should be noted This document was dra fted in accordance with the editorial rules of the ISO/IEC Directives, Part (see www.iso org/directives) Attention is drawn to the possibility that some o f the elements o f this document may be the subject o f patent rights ISO shall not be held responsible for identi fying any or all such patent rights Details o f any patent rights identified during the development o f the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso org/patents) Any trade name used in this document is in formation given for the convenience o f users and does not constitute an endorsement For an explanation on the voluntary nature o f standards, the meaning o f ISO specific terms and expressions related to formity assessment, as well as in formation about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso org/iso/foreword html This document was prepared by Technical Committee ISO/TC 102, , Subcommittee SC 2, This third edition cancels and replaces the second edition (ISO 4689-2:2015), which constitutes a minor revision with the following changes: — 6.7: first line, a fter “approximately”, insert “10 g”; — 9.2.4: modi fy Formula (7) and the relevant descriptions, to harmonize this subclause across all standards for which ISO/TC 102/SC is responsible A list of all parts in the ISO 4689 series can be found on the ISO website Iron ore an d direct reduced iron Ch emical an alysis iv © ISO 2017 – All rights reserved ISO 4689-2 : 01 7(E) Introduction T h i s c u ment wa s origi na l ly publ i s he d a s I S O 69 : 19 Under a p ol ic y o f rationa l i z ation o f the nu mb eri ng s ys tem u s e d i n I S O/ TC 102 , it has b e en de c ide d to re - de s ignate th i s c u ment as I S O -2 It was further decided to introduce a combustion/infrared method, numbered ISO 4689-3 When next revised, ISO 4689:1986 will be re-designated as ISO 4689-1 © ISO 2017 – All rights reserved v INTERNATIONAL STANDARD ISO 4689-2 : 01 7(E) Iron ores — Determination of sulfur content — Part 2: Combustion/titration method WARNING — This document may involve hazardous materials, operations, and equipment This document does not purport to address all of the safety problems associated with its use It is the responsibility of the user of this document to establish appropriate health and safety practices and determine the applicability of regulatory limitations prior to use Scope T h i s c ument s p e c i fie s a combu s tion/titration me tho d for the de term i nation o f the s u l fu r content o f iron ores This method is applicable to sulfur contents between 0,002 % (mass fraction) and 0,25 % (mass fraction) in natural iron ores, iron ore concentrates, and agglomerates, including sinter products The re s u lts are no t a ffe c te d b y the pre s ence o f fluoride T he Normative references fol lowi ng c u ments are re ferre d to i n the tex t i n s uch a way th at s ome or a l l o f thei r content s titute s re qu i rements o f th i s c u ment For date d re ference s , on ly the e d ition cite d appl ie s For u ndate d re ference s , the late s t e d ition o f the re ference d c ument (i nclud i ng a ny amend ments) appl ie s ISO 385, ISO 648, ISO 1042, Laboratory glassware — One-mark volumetric flasks ISO 2596, Laboratory glassware — Burettes Laboratory glassware — Sin gle-volum e pipettes Iron ores — Determin ation of hygroscopic m oisture in an alytical samples — Gravim etric, Karl Fisch er an d m ass-loss m eth ods ISO 3082, ISO 7764, ISO Guide 35, Reference materials — General and statistical principles for certification Iron ores — Sam plin g an d sample preparation procedures Iron ores — Preparation of predried test samples for ch emical an alysis Terms and definitions No term s and defi nition s a re l i s te d i n th i s c u ment ISO and IEC maintain terminological databases for use in standardization at the following addresses: — IEC Electropedia: available at http://www.electropedia org/ — ISO Online browsing platform: available at http://www.iso org/obp Principle The sample is mixed with tungsten(VI) oxide and heated at 200 °C in a resistance furnace, using nitrogen as a carrier gas © ISO 2017 – All rights reserved ISO 4689-2 : 01 7(E) T he evolve d s u l fu r d ioxide is ab s orb e d in d i lute hyd ro ch loric acid s olution contai n i ng s ta rch and p o ta s s iu m io d ide, and the s olution i s titrate d conti nuou s ly du ri ng evolution with a s tandard volu me tric solution of potassium iodate Reagents D u ri ng ana lys i s , u s e on ly re agents o f re co gn i ze d ana lytic a l grade, and on ly d i s ti l le d water or water o f e qu iva lent pu rity , Mg(ClO 4) Magnesium perchlorate Tungsten(VI) oxide Tin(II) chloride Sodium hydroxide coated silica 5 Hydrochloric acid Potassium iodide , anhydro us , free flowing, p article s ize , mm to mm , (WO ) , SnCl2 ·2H O, particle size 0,5 mm to mm , particle size 0,5 mm to mm , ρ, 1,16 g/ml to 1,19 g/ml, diluted + 66 , KI, % (mass fraction) solution , % (mass fraction) solution Make a suspension of 2,0 g of starch in 10 ml of water, add to 50 ml of boiling water and stir Cool, dilute to 100 ml and mix Starch P rep are th i s s olution i m me d i ately prior to u s e Potassium iodate , KIO , standard volumetric solution, 0,001 042 mol/l T he p o tas s iu m io date s hou ld b e previou sly d rie d for h at ° C Weigh, to the nearest 0,000 g, 0,223 g of dried potassium iodate and dissolve in water Cool, transfer to a l volu me tric flas k, d i lute to volu me and m i x ml of this standard volumetric solution is equivalent to 0,10 mg of sulfur Apparatus O rd i na r y lab orator y app aratu s , i nclud i ng one -mark pip e tte s and one -mark volu me tric fla s ks complyi ng with the s p e ci fic ation s o f I S O and I S O 10 42 re s p e c tively, a s wel l a s the See Figure 6.1 Nitrogen supply 6.2 Drying tower, 6.3 Flowmeter 6.4 Resistance furnace 6.5 Refractory combustion tube fol lowi ng co ntaining s o dium hydroxide co ated s ilica ( 5.4) and magnesium perchlorate (5.1) , graduated from to l/min , capable of maintaining a temperature of 200 °C ± 25 °C , capable of withstanding a temperature of 200 °C ± 25 °C © ISO 2017 – All rights reserved ISO 4689-2 : 01 7(E) , with loose-fitting lid, or a suitable re fractory combustion boat 6.6 Refractory combustion boat 6.7 Tin(II) chloride absorption tube capable of accommodating a porous cartridge, as shown in Figure a) or b) respectively The following dimensions can be used as guidelines Combustion boat Cartridge Length 80 mm Length 50 mm Width 13 mm Internal diameter 15 mm Depth mm , o f narrow glass tubing containing approximately 10 g o f solid tin(II) chloride (5.3 ), suitably plugged with inert wool to prevent the reagent being blown into the absorption vessel A U-tube is suitable Where necessary, this is inserted in the train at the exit o f the combustion tube at point X in Figure If the sample is known or thought to contain chloride, e.g in the form of sodium chloride, chlorapatite, or scapolite, the chlorine formed during combustion o f the sample should be removed by passing the gas stream through solid tin(II) chloride in a suitable tube or vessel (6.7) prior to absorption and titration I f numerous samples having chloride contents >1 (mass fraction) are to be analysed, it is advisable to determine the absorption capacity o f the tin(II) chloride in order to be able to judge the most suitable interval for reagent replacement In such cases, a larger absorption vessel may be pre ferred The tin(II) chloride absorption tube should also be fitted i f the chloride content o f the test sample is unknown 6.8 Cylinder 6.9 Bubbler , 100 ml, tall form, to hold the absorbing solution , multi-hole, to reach to the bottom o f the cylinder (6.8) , conforming to ISO 385, graduated in divisions of 0,05 ml For determination of low sulfur contents [the equivalent o f 0,001 % (mass fraction) in the test sample], this may be due to the presence o f sul fur compounds either in the tungsten(VI) oxide or in the re fractory boats/porous cartridges used Tungsten(VI) oxide (5.2 ) can be pre-treated by heating for h at a temperature of 800 °C, and the blank in the combustion boats/cartridges can be reduced by allowing them to stand overnight in a suitable furnace at a temperature of 200 °C and then storing in a desiccator prior to use Such pre-treatment of tungsten(VI) oxide and the combustion boats is also required if the sulfur content of the test sample is less than 0,01 % (mass fraction) © ISO 2017 – All rights reserved ISO 4689-2 : 01 7(E) Expression of results 9.1 Calculation of sulfur content The sulfur content, ws f than 0,01 % and to six decimal places for contents lower than 0,01 %, using Formula (1) , i s ca lc u late d a s a p ercentage b y ma s s , to five de ci ma l place s w s (%) = where V1 or contents h igher V1 − V2 m × 100 (1) is the volume, in millilitres, of standard potassium iodate solution (5.8) used in the titration of the te s t p or tion; V2 is the volume, in millilitres, of standard potassium iodate solution (5.8) used in the blank titration; is the mass, in grams, of the test portion m 9.2 General treatment of results 9.2 Repeatability and permissible tolerance T he pre c i s ion o f th i s a na lytic a l me tho d i s e xpre s s e d b y the Additional information is given in Annexes B and C NOTE Rd fol lowi ng formu l ae: = 0, 011 98 (2) X 518 , (3) P = 114 59 X + 000 85 , , , 004 233 X , 038 70 X σd = σL = (4) , 518 (5) + 0, 000 23 where Rd i ndep endent dupl ic ate l i m it; P i s the p erm i s s ible tolerance b e twe en lab oratorie s; σd i s the i ndep endent dupl ic ate s ta ndard devi ation; σL i s the b e twe en-lab oratorie s s ta nda rd deviation; X - i s the s u l fu r content, e xpre s s e d as a p ercentage b y ma s s , o f the pre d rie d te s t s a mple c a lc u lat ed as follows: Formulae (2) and (4) — between-laboratories Formulae (3) and (5) of the two laboratories — with i n-l ab orator y © ISO 2017 – All rights reserved : the arith me tic me a n o f the dupl ic ate va lue s; : the arith me tic me an o f the fi na l re s u lts ( 9.2.5) ISO 4689-2 : 01 7(E) 9.2 Determination of analytical result Having computed the independent duplicate results according to Formula (1), compare them with the independent duplicate limit, Rd, using the procedure given in Annex A 9.2 Between-laboratories precision B e twe en-l ab oratorie s pre c i s ion i s u s e d to de term i ne the agre ement b e twe en the fi na l re s u lts rep or te d by two lab oratorie s T he as s u mp tion i s that b o th l ab oratorie s in 9.2.2 C ompute the µ 1,2 = fol lowi ng fol lowe d the s ame pro ce dure de s crib e d qua ntity: µ1 + µ2 (6) where μ1 i s fi na l re s u lt rep or te d by lab orator y ; μ2 i s the fi na l re s u lt rep or te d b y l ab orator y ; μ1,2 i s the me an o f fi na l re s u lts If µ − µ ≤ P , the results are in agreement 9.2 Check for trueness T he truene s s o f the ana lytic a l me tho d sh a l l b e che cke d by applyi ng it to a cer ti fie d re ference materi a l (CRM) or a reference material (RM) The procedure is the same as that described above After f f value, Ac There are two possibilities: ff f a) µ c − Ac ≤ C fi rmation o the pre c i s ion, the fi na l lab orator y re s u lt i s comp a re d with the re erence or cer ti fie d i n wh ich c as e the d i erence b e twe en the rep or te d re s u lt a nd the re erence/cer ti fie d va lue i s s tati s tic a l ly i n s ign i fic ant b) µ c − A c > C i n wh ich c as e the d i fference b e twe en the rep or te d re s u lt a nd the re ference/cer ti fie d va lue i s s tati s tic a l ly s ign i fic ant where μc i s the fi na l re s u lt Ac i s the re ference/cer ti fie d va lue C i s a va lue dep endent on the typ e o f C RM/RM u s e d for the cer ti fie d re ference materi a l; C er ti fie d re ference materi a l s u s e d ISO Guide 35 C should be calculated as follows: C=2 where s Lc + s Wc n Wc Nc + σ L2 + σ d2 n for for th i s the C RM/RM ; pu rp o s e shou ld b e prep are d and cer ti fie d i n accorda nce with (7) © ISO 2017 – All rights reserved ISO 4689-2 : 01 7(E) sLc is the between-laboratories standard deviation o f the certi fying laboratories; sWc is the within-laboratory standard deviation o f the certi fying laboratories; n Wc is the average number o f replicate determinations in the certi fying laboratories; Nc is the number o f certi fying laboratories; n is the number o f replicate determinations carried out on the CRM/RM; σL and σd are as defined in 9.2.1 The following procedure should be used when the in formation on the re ference material certificate is incomplete — I f there are su fficient data to enable the between-laboratories standard deviation to be estimated, delete the expression s Wc / n Wc and regard sLc as the standard deviation o f the laboratory means; — I f the certification has been made by only one laboratory or i f the interlaboratory results are missing, use the following condition: σ L2 + C=2 σ d2 (8) n A CRM certified by only one laboratory should be avoided, unless it is known to have an unbiased certified value C a l c u l a t i o n o f f i n a l r e s u l t The final result is the arithmetic mean o f the acceptable analytical values for the test sample, or as otherwise determined by the operations specified in Annex A , calculated to five decimal places for contents of sulfur higher than 0,01 % (mass fraction) and to six decimal places for contents lower than 0,01 % (mass fraction) For contents higher than 0,01 % (mass fraction), the value is rounded off to the third decimal place as specified in a), b), and c) In a similar manner, with the ordinal numbers increased by one, the value for sul fur contents lower than 0,01 % (mass fraction) is rounded o ff to the fourth decimal place a) Where the figure in the fourth decimal place is less than five, it is discarded and the figure in the third decimal place is kept unchanged b) Where the figure in the fourth decimal place is five and there is a figure other than in the fi fth decimal place, or i f the figure in the fourth decimal place is greater than five, the figure in the third decimal place is increased by one c) Where the figure in the fourth decimal place is five and the figure is in the fi fth decimal place, the five is discarded and the figure in the third decimal place is kept unchanged, i f it is 0, 2, 4, 6, or 8, and is increased by one, i f it is 1, 3, 5, 7, or Test report The test report shall include the following information: a) the name and address o f the testing laboratory; b) the date o f issue o f the test report; c) a re ference to this document, i.e ISO 4689-2; d) the details necessary for the identification o f the sample; © ISO 2017 – All rights reserved ISO 4689-2 : 01 7(E) e) the re s u lt o f the a na lys i s; f) the re ference nu mb er o f the re s u lt; g) any charac teri s tics no tice d du ri ng the de term i nation, and any op eration s no t s p e ci fie d i n th i s p ar t o f I S O 9, wh ich may have h ad an i n fluence on the re s u lt, either for the te s t s ample or for the cer ti fie d re ference materia l(s) 10 © ISO 2017 – All rights reserved ISO 4689-2 : 01 7(E) Annex A (normative) Flowsheet of the procedure for the acceptance of analytical values for test samples Start with independent duplicate results x1 x2 Yes Rd = x1 Yes = x1 x2 Yes = x1 x2 x2 No One more determination x max x 1,2 R d x3 No One more determination x max x 1,3 R d x3 x4 No = Median ( x , x , x , NOTE x4 ) Rd i s a s de fi ne d i n 9.2.1 Figure A.1 — Flowsheet of the procedure for the acceptance of analytical values for test samples © ISO 2017 – All rights reserved 11 ISO 4689-2 : 01 7(E) Annex B (informative) Derivation of repeatability and permissible tolerance equations The regression formulae in 9.2.1 f f out in 1999/2000 on seven iron ore samples, involving six laboratories in four countries Graphical treatment of the precision data is given in Annex C The test samples used are listed in Table B.1 were derive d rom the re s u lts o i nternationa l ana lytica l tria l s c arrie d NO TE Rep o r ts o f the i nter n atio n a l tr i a l a nd a s tati s tic a l a n a l ys i s o f the re s u lts ( D o c u ments I S O/ TC 10 /S C NO TE T he s tati s tic a l a n a l ys i s wa s p er fo r me d i n acco rda nce with the p ri nc ip le s emb o d ie d i n I S O -2 N1419 and N1422, September 2000) are available from the Secretariat of ISO/TC 102/SC Table B — Sulfur contents of test samples S ample WG 4-5 WG 4-3 WG 4-4 WG 4-1 WG 4-2 WG 4-6 WG 4-7 12 Sulfur content % (mass fraction) 0,004 50 0,005 79 0,011 0,208 0,032 0,110 0,527 © ISO 2017 – All rights reserved ISO 4689-2 : 01 7(E) Annex C (informative) Precision data obtained by international analytical trial Figure C.1 is a graphical presentation of the formulae in 9.2.1 Y 0,06 P 0,05 0,04 0,03 σ 0,02 L 0,01 Rd σ d Key X Y 0 ,1 ,2 0,3 ,4 0,5 X ulfur content, % mass fraction p recision, % s F i g u r e C © ISO 2017 – All rights reserved — L e a s t - s q u a r e s f i t o f p r e c i s i o n a g a i n s t X f o r s u l f u r 13 ISO 4689-2 : 01 7(E) Bibliography [1] ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method 14 © ISO 2017 – All rights reserved