1、BRITISH STANDARD BS7020-22: 1990 ISO 9035:1989 Analysis of iron ores Part 22: Method for the determination of acid-soluble iron (II) content: titrimetric method UDC 622.341.1:620.13:622.7.016.34:5432:541.8:546.72:543.24:620.1BS7020-22:1990 This British Standard, having been prepared under the direct
2、ionof the Iron and Steel Standards Policy Committee, waspublished under the authorityof the Board of BSI andcomes into effect on 28 February1990 BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference ISM/58 Draft for comment 88/36367 DC ISBN 0 580 18074 3 C
3、ommittees responsible for this British Standard The preparation of this British Standard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) to Technical Committee ISM/58, upon which the following bodies were represented: British Steel Industry Institution of Mining and Metallurgy
4、 The following body was also represented in the drafting of the standard, through subcommittees and panels: British Ceramic Research Ltd. Amendments issued since publication Amd. No. Date of issue CommentsBS7020-22:1990 BSI 10-1999 i Contents Page Committees responsible Inside front cover National f
5、oreword ii 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Sampling and samples 1 7 Procedure 2 8 Expression of results 2 9 Test report 4 Annex A (normative) Flowsheet of the procedure for the acceptance of analytical values for test samples 5 Annex B (informative) Deri
6、vation of repeatability and permissible tolerance equations 6 Annex C (informative) Precision data obtained by international analytical trial 7 Figure C.1 Least-squares fit of precision against X for acid-soluble iron(II) 7 Table B.1 Acid-soluble iron(II) contents of the test samples 6 Publications
7、referred to Inside back coverBS7020-22:1990 ii BSI 10-1999 National foreword This Part of BS7020 has been prepared under the direction of the Iron and Steel Standards Policy Committee. It is identical with ISO9035:1989 “Iron ores Determination of acid-soluble iron (II) content Titrimetric method” pu
8、blished by the International Organization for Standardization (ISO). The Technical Committee has reviewed the provisions of ISO7215:1985, to which reference is made in the text and has decided that they are acceptable for use in conjunction with this standard. A related British Standard to ISO385-1:
9、1984 is BS846:1985 “Specification for burettes”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal oblig
10、ations. Cross-references International Standard Corresponding British Standard ISO4695:1984 BS6598:1985 Method for determination of reducibility of iron ores (Identical) ISO4791-1:1985 BS6711 Vocabulary relating to laboratory apparatus made essentially from glass, porcelain or vitreous silica Part 1
11、:1986 Names for items of apparatus (Identical) ISO7764:1985 BS7020 Analysis of iron ores Part 1:1988 Method for the preparation of pre-dried test samples for chemical analysis (Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to8, an insi
12、de back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7020-22:1990 BSI 10-1999 1 1 Scope This International Standard specifies a method for the determinat
13、ion of iron(II) content in natural and processed iron ores containing from1% to25% acid-soluble iron(II) and only traces of metallic iron. This method is specifically limited for use in conjunction with the reducibility test methods specified in ISO4695 or ISO7215. This method is not applicable to o
14、res containing more than0,3% (m/m) sulfur (as sulfide) and/or5% (m/m) free carbon. Experiments have shown that the acid-insoluble residue can be neglected, especially as regards the needs of the reducibility test methods concerned and the precision obtainable. 2 Normative references The following st
15、andards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged
16、to investigate the possibility of applying the most recent editions of the standards listed below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO385-1:1984, Laboratory glassware Burettes Part 1: General requirements. ISO4695:1984, Iron ores Determination of
17、 reducibility. ISO4791-1:1985, Laboratory apparatus Vocabulary relating to apparatus made essentially from glass, porcelain or vitreous silica Part1:Names for items of apparatus. ISO7215:1985, Iron ores Determination of relative reducibility. ISO7764:1985, Iron ores Preparation of predried test samp
18、les for chemical analysis. 3 Principle Dissolution with hydrochloric acid in an inert atmosphere, addition of a mixture of sulfuric and phosphoric acid and dilution with water. Determination of the iron(II) content by titration with potassium dichromate standard solution using sodium diphenylaminesu
19、lfonate as indicator. 4 Reagents During the analysis, use only reagents of recognized analytical grade, and only distilled water or water of equivalent purity. NOTEThe water used for the procedure should be de-oxygenated by boiling. 4.1 Sodium carbonate (Na 2 CO 3 ) or sodium hydrogen carbonate (NaH
20、CO 3 ). 4.2 Hydrochloric acid , 1,16g/ml to1,19g/ml. NOTEThis reagent should be de-oxygenated by purging with either nitrogen or argon, or by heating for a short time. 4.3 Hydrofluoric acid, 40% (m/m), 1,13g/ml or48% (m/m), 1,16g/ml. 4.4 Sodium carbonate or sodium hydrogen carbonate, saturated solut
21、ion, at ambient temperature. 4.5 Sulfuric acid phosphoric acid mixture. To300ml of water, add cautiously150ml of sulfuric acid ( 1,84g/ml), with constant stirring. After cooling, add150ml of phosphoric acid( 1,71g/ml). Cool and dilute with water to1000ml. 4.6 Nitrogen (99,99% N 2 ) or argon (optiona
22、l). 4.7 Potassium dichromate, standard volumetric solution, c(K 2 Cr 2 O 7 ) =0,016 67mol/l. Dissolve4,904g of pulverized potassium dichromate (dried at140 C to150 C for2h and cooled to room temperature in a desiccator) in water and dilute to a volume of1000ml after cooling to20 C. 4.8 Sodium diphen
23、ylaminesulfonate solution Dissolve0,2g of powdered sodium diphenylaminesulfonate (C 6 H 5 NHC 6 H 4 SO 3 Na) in100ml of water. Store the solution in a brown glass bottle. NOTE 1Alternatively, an equivalent quantity of indicator in pellet form may be used. NOTE 2Barium diphenylaminesulfonate may be u
24、sed instead of sodium diphenylaminesulfonate. 5 Apparatus Ordinary laboratory apparatus, and 5.1 Conical flask, of capacity500ml. 5.2 Gckel safety trap (see ISO4791-1) or an apparatus with a feed tube for inert gas. NOTEAlternatively, a slit rubber valve (Bunsen valve) may be used, but its efficienc
25、y depends on the length of the slit and the quality and flexibility of the rubber tubing. 5.3 Burette, class B, conforming with ISO385-1. 6 Sampling and samples 6.1 Laboratory sample Crush and pulverize the whole of one of the test portions for the reducibility test, which has been reserved for chem
26、ical analysis, down to minus1004m particle size. In the case of ores with significant contents of combined water or oxidizable compounds, use a particle size of minus1604m. NOTEA guideline on significant contents of combined water and oxidizable compounds is incorporated in ISO7764.BS7020-22:1990 2
27、BSI 10-1999 6.2 Preparation of predried test samples Thoroughly mix the laboratory sample using non-magnetic materials. Taking multiple increments with a non-magnetic spatula, extract a test sample in such a manner that it is representative of the whole contents of the container. Dry the test sample
28、 at105 C 2 C as specified in ISO7764. (This is the predried test sample.) 7 Procedure 7.1 Number of determinations Carry out the analysis at least in duplicate in accordance with Annex A, independently, on one predried test sample. NOTEThe expression “independently” means that the second and any sub
29、sequent result is not affected by the previous result(s). For this particular analytical method, this condition implies that the repetition of the procedure shall be carried out either by the same operator at a different time, or by a different operator, including, in either case, appropriate recali
30、bration. 7.2 Check test In each run, one analysis of a certified reference material of the same type of ore shall be carried out in parallel with the analysis of the ore sample(s) under the same conditions. A predried test sample of the certified reference material shall be prepared as specified in6
31、.2. When the analysis is carried out on several samples of the same type of ore at the same time, the analytical value of one certified reference material may be used. NOTE 1The certified reference material should be of the same type as the sample to be analysed and the properties of the two materia
32、ls should be sufficiently similar to ensure that in either case no significant changes in the analytical procedure will become necessary. NOTE 2The certified reference material is used only to validate the performance of the analytical procedure and expressly not to standardize the potassium dichrom
33、ate solution. 7.3 Test portion Taking several increments, using a non-magnetic spatula, weigh to the nearest0,0002g approximately0,5g of the predried test sample obtained in accordance with6.2. NOTEThe test portion should be taken and weighed quickly to avoid reabsorption of moisture. 7.4 Decomposit
34、ion Transfer the predried test portion (7.3) to a dry500ml conical flask (5.1) and add1g to2g of solid sodium hydrogen carbonate or sodium carbonate (4.1) and30ml of hydrochloric acid (4.2). For ores with high silica contents i.e.U 5% (m/m) SiO 2 , add a few drops of hydrofluoric acid (4.3). Immedia
35、tely close the flask with a Gckel safety trap (5.2) which contains sodium hydrogen carbonate or sodium carbonate solution (4.4) or is to be flushed with nitrogen or argon (4.6) at0,5l/min during the decomposition. Heat the flask on a heating plate at a temperature of about90 C until complete decompo
36、sition of the test portion. NOTEThe decomposition time should not exceed60min. Normally a decomposition time of30min is sufficient. In order to ensure the complete decomposition of the sample, a duplicate determination may be performed using twice the decomposition time, provided that this time does
37、 not exceed60min. When the closed flask has cooled, remove the valve and wash away the iron chlorides adhering to the stem of the valve with water. 7.5 Titration Add30ml of sulfuric acid phosphoric acid mixture (4.5) to the solution, dilute with water to about300ml and add about5 to6 drops of sodium
38、 diphenylaminesulfonate solution (4.8) as an indicator. Titrate immediately with the potassium dichromate standard solution (4.7) until the colour of the solution changes from green to bluish green to violet with the last drop of the titrant. NOTEThe ambient temperature of the potassium dichromate s
39、olution should be noted. If it differs by more than2 C from the temperature at which it was prepared, make the appropriate volumetric correction:0,02% relative for each1 C of difference, i.e.the titre should be decreased when the ambient temperature during the titration is higher than the temperatur
40、e during preparation of the standard volumetric solution. 8 Expression of results 8.1 Calculation of iron(II) content The iron(II) content, expressed as a percentage by mass, is calculated to three decimal places using the equation . . . (1) where V is the volume, in millilitres, of potassium dichro
41、mate solution (4.7) required for sample analysis; m is the mass, in grams, of the predried sample; 0,558 5is a multiple of the atomic mass of iron.BS7020-22:1990 BSI 10-1999 3 8.2 General treatment of results 8.2.1 Repeatability and permissible tolerance The precision of this analytical method is ex
42、pressed by the following regression equations 1)8.2.2 Acceptance of analytical values The result obtained for the certified reference material shall be such that the difference between this result and the certified value of the certified reference material is statistically insignificant. For a certi
43、fied reference material that has been analysed by at least10 laboratories using method(s) that are comparable both in accuracy and precision with this method, the following condition may be used to test the significance of the difference: If condition (6) is satisfied, i.e.if the left-hand side is l
44、ess than or equal to the right-hand side, then the differenceis statistically insignificant; otherwise it is statistically significant. When the difference is significant, the analysis shall be repeated, simultaneously with an analysis of the test sample. If the difference is again significant, the
45、procedure shall be repeated using a different certified reference material of the same type of ore. When the range of the two values for the test sample is outside the limit for r calculated according to equation (2) in8.2.1, one or more additional tests shall be carried out. Acceptability of the re
46、sults for the test sample shall, in each case, be subject to the acceptability of the results for the certified reference material. NOTEThe following procedure should be used when the information on the reference material certificate is incomplete: a) if there are sufficient data to enable the betwe
47、en-laboratories standard deviation to be estimated, delete the expression s 2 Wc /n Wcand regard s Lcas the standard deviation of the laboratory means; b) if the certification has been made by only one laboratory or if the inter-laboratory results are missing, it is advisable that this material not
48、be used in the application of the standard. In case its use is unavoidable, use the formula r = 0,015 3 X + 0,060 0 . . . (2) P = 0,021 5 X + 0,180 6 . . . (3) r = 0,005 4 X + 0,021 2 . . . (4) L = 0,006 6 X + 0,062 7 . . . (5) where X is the iron(II) content, as a percentage by mass, of the test sa
49、mple, calculated as follows: within-laboratory equations (2 and 4): the arithmetic mean of the duplicate values; between-laboratories equations (3 and 5): the arithmetic mean of the final results (8.2.3) of the two laboratories; r is the permissible tolerance within a laboratory (repeatability); P is the permissible tolerance between laboratories; r is the within-laboratory standard deviation; L is the between-laboratories standard deviation. 1) Additional information is given in Annex B and Annex C. . . . (6) where A
