1、BRITISH STANDARD BS7020-5.1: 1993 ISO2598-1: 1992 Analysis of iron ores Part 5: Methods for the determination of silicon content Section 5.1 Gravimetric methods UDC 553.31:543.21:546.28BS7020-5.1:1993 This British Standard, having been prepared under the directionof the Iron and SteelStandards Polic
2、y Committee, waspublished underthe authorityof the Standards Boardand comes intoeffect on 15 October1993 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference ISM/58 Draft for comment91/35108 DC ISBN 0 580 22291 8 Committees responsible for this British St
3、andard 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 Coopted members The following body was a
4、lso represented in the drafting of the standard, through subcommittees and panels: British Ceramic Research Ltd. Amendments issued since publication Amd. No. Date CommentsBS7020-5.1:1993 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Normative
5、references 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Sampling and samples 2 7 Procedure 2 8 Expression of results 4 9 Test report 5 Annex A (normative) Flowsheet of the procedure for the acceptance of analytical values for test samples 6 Annex B (informative) Derivation of repeatability and permi
6、ssible tolerance equations 7 Annex C (informative) Precision data obtained by international analytical trials 7 Figure C.1 Least-squares fit of precision against X for silicon 7 Table 1 Mass of test portion 2 Table B.1 Silicon contents of test samples 7 List of references Inside back coverBS7020-5.1
7、:1993 ii BSI 07-1999 National foreword This Section of BS7020 has been prepared under the direction of the Iron and Steel Standards Policy Committee and is identical with ISO2598-1:1992 Iron ores Determination of silicon content Part1: Gravimetric methods published by the International Organization
8、for Standardization (ISO). It supersedes BS4158-3:1972, which is withdrawn. The Technical Committee has reviewed the provisions of ISO648, to which normative reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A related British Standard
9、to ISO648:1977 is BS1583:1986 Specification for one-mark pipettes. 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 immunit
10、y from legal obligations. Cross-references International standard Corresponding British Standard ISO1042:1983 BS1792:1982 Specification for one-mark volumetric flasks (Identical) ISO2596:1984 BS7020 Analysis of iron ores Part2:1988 Method for the determination of hygroscopic moisture in analytical s
11、amples (Identical) BS5660 Methods of sampling iron ores ISO3081:1986 Part1:1987 Manual method of increment sampling (Identical) ISO3082:1987 Part2:1987 Mechanical method of increment sampling and sample preparation (Identical) ISO3083:1986 BS5661:1987 Method for preparation of samples of iron ores b
12、y manual means (Identical) ISO7764:1985 BS7020 Analysis of iron ores Part1:1988 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 inside back cover and a b
13、ack 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.BS7020-5.1:1993 BSI 07-1999 1 1 Scope This part of ISO2598 specifies two gravimetric methods for the determination of the s
14、ilicon content of iron ores. These methods are applicable, with certain limitations, to silicon contents between1% (m/m) and15 % (m/m) in natural iron ores, iron ore concentrates and agglomerates, including sinter products. Method1 is not applicable to iron ores having a content of reducing agents g
15、reater than2 % (m/m), for instance pyrite, or to ores having a fluorine content greater than0,1 % (m/m). It is recommended for lower grade ores having a high content of amphoteric elements. Method2 can be used for ores having a fluorine content greater than0,1 % (m/m). It is recommended for high gra
16、de ores having a low content of gangue. NOTE 1For ores having a silicon content less than5 % (m/m), the method specified in ISO2598-2: 1) , Iron ores Determination of silicon content Part2: Reduced molybdosilicate spectrophotometric method, is preferable. 2 Normative references The following standar
17、ds contain provisions which, through reference in this text, constitute provisions of this part of ISO2598. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO2598 are encouraged to investigate the
18、possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO648:1977, Laboratory glassware One-mark pipettes. ISO1042:1983, Laboratory glassware One-mark volumetric flasks. ISO2596:1984, I
19、ron ores Determination of hygroscopic moisture in analytical samples Gravimetric and Karl Fischer methods. ISO3081:1986, Iron ores Increment sampling Manual method. ISO3082:1987, Iron ores Increment sampling and sample preparation Mechanical method. ISO3083:1986, Iron ores Preparation of samples Man
20、ual method. ISO7764:1985, Iron ores Preparation of predried test samples for chemical analysis. 3 Principle Decomposition of the test portion, by either method1 or method2. Method1: Decomposition by sintering with sodium peroxide, followed by treatment with hydrochloric and perchloric acids, or Meth
21、od2: Decomposition by treatment with hydrochloric, nitric and perchloric acids (with inclusion of boric acid, if necessary) and evaporation to fumes of perchloric acid. Filtration of silica together with any residue, fusion with sodium carbonate and dissolution in hydrochloric and perchloric acids.
22、Evaporation of the solution from either method1 or method2 to fumes of perchloric acid and filtration of the precipitated silica. Ignition of the impure silica and weighing. Treatment of the ignited residue with hydrofluoric and sulfuric acids, followed by ignition and reweighing. 4 Reagents During
23、the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Sodium peroxide (Na 2 O 2 ), powder. 4.2 Boric acid (H 3 BO 3 ). To be used as in note7. 4.3 Sodium carbonate (Na 2 CO 3 ), anhydrous. 4.4 Hydrochloric acid, 1,16g/ml to1,19g/ml
24、. 4.5 Hydrochloric acid, 1,16g/ml to1,19g/ml, diluted1+1. 4.6 Hydrochloric acid, 1,16g/ml to1,19g/ml, diluted1+9. 4.7 Perchloric acid, 1,67g/ml,70 % (m/m), or 1,54g/ml,60 % (m/m). 4.8 Sulfuric acid, 1,84g/ml, diluted1+1. 4.9 Sulfuric acid, 1,84g/ml, diluted1+9. 4.10 Hydrofluoric acid, 1,13g/ml,40 %
25、(m/m), or 1,185g/ml,48 % (m/m). 4.11 Nitric acid, 1,4g/ml. 5 Apparatus Ordinary laboratory apparatus, including one-mark pipettes and one-mark volumetric flasks complying with the specifications of ISO648 or ISO1042 respectively, and 5.1 Nickel, zirconium or vitreous carbon crucibles, of capacity ap
26、proximately40ml. 5.2 Platinum crucibles, of capacity approximately40ml. 1) To be published. (At present published as ISO4686:1980.)BS7020-5.1:1993 2 BSI 07-1999 5.3 Nickel spatula 5.4 Muffle furnaces, adjustable to400 C 20 C and to temperatures up to1050 C. 6 Sampling and samples 6.1 Laboratory samp
27、le For analysis, use a laboratory sample of minus1004m particle size which has been taken in accordance with ISO3081 or ISO3082 and prepared in accordance with ISO3082 or ISO3083. In the case of ores having significant contents of combined water or oxidizable compounds, use a particle size of minus1
28、604m. NOTE 2A guideline on significant contents of combined water and oxidizable compounds is incorporated in ISO7764. 6.2 Preparation of test samples Depending on the ore type, proceed in accordance with either6.2.1 or6.2.2. 6.2.1 Ores having significant quantities of combined water or oxidizable c
29、ompounds and silica contents above10 % (m/m) Where the silica content is above10 % (m/m), prepare an air-equilibrated test sample in accordance with ISO2596 for the following types of ores: a) processed ores containing metallic iron; b) natural or processed ores in which the sulfur content is higher
30、 than0,2 % (m/m); c) natural or processed ores in which the content of combined water is higher than2,5 % (m/m). 6.2.2 Ores outside the scope of6.2.1 Prepare a predried test sample as follows: Thoroughly mix the laboratory sample and, taking multiple increments, extract a test sample in such a manne
31、r that it is representative of the whole contents of the container. Dry the test sample 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 tes
32、t sample. NOTE 3The expression “independently” means that the second and any subsequent result is not affected by the previous result(s). For this particular analytical method, this condition implies that the repetition of the procedure is carried out either by the same operator at a different time
33、or by a different operator including, in either case, appropriate recalibration. 7.2 Test portion Taking several increments, weigh, to the nearest0,0002g, approximately the amount of the predried test sample indicated in Table 1. Table 1 Mass of test portion NOTE 4The test portion should be taken an
34、d weighed quickly to avoid reabsorption of moisture. 7.3 Blank test and check test In each run, one blank test and 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
35、 sample of the certified reference material shall be prepared as specified in6.2.2. NOTE 5The certified reference material should be of the same type as the sample to be analysed and the properties of the two materials should be sufficiently similar to ensure that in either case no significant chang
36、es in the analytical procedure will become necessary. When the analysis is carried out on several samples at the same time, the blank value may be represented by one test, provided that the procedure is the same and that the reagents used are from the same reagent bottles. When the analysis is carri
37、ed 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. 7.4 Determination 7.4.1 Decomposition of the test portion If the decomposition is to be based on alkali sintering, proceed as specified in7.4.1.1; if it is to be
38、based on acid attack, proceed as specified in7.4.1.2. 7.4.1.1 Alkali sinter attack (Method1) Place the test portion(7.2) in a nickel, zirconium or vitreous carbon crucible(5.1), add3g of sodium peroxide(4.1), mix thoroughly using the nickel spatula(5.3) and tamp the mixture. Place the crucible in th
39、e entrance of the muffle furnace(5.4), set at 400 C 20 C, and leave for1min to2min. Place the crucible in the furnace, maintained at the same temperature, and leave for1h. Remove the crucible from the furnace and allow to cool in a desiccator. NOTE 6The mixture should not reach the melting point. Sh
40、ould this happen, it is recommended that the operation be repeated at a lower temperature. Si content % (m/m) Mass of test portion g 1 to10 10 to15 1,0 0,5BS7020-5.1:1993 BSI 07-1999 3 WARNING Protective goggles should be worn during the following operation. Transfer the crucible containing the sint
41、ered mass to a600ml low-form beaker. Cover the beaker with a watch-glass and carefully add200ml of water. Add50ml of hydrochloric acid(4.4) and25ml of perchloric acid(4.7) to dissolve the sintered mass. Remove the crucible from the beaker and rinse it with hydrochloric acid(4.6) and water. Scrape ou
42、t the rest of the sintered mixture adhering to the walls of the crucible, using a rubber-tipped glass rod. Place the beaker on a hot-plate and heat the solution gently to decompose the sintered products completely. Add1ml of sulfuric acid(4.9) to prevent precipitation of titanium. Partially uncover
43、the beaker and heat until dense white fumes of perchloric acid appear. Cover the beaker completely and continue heating until there are no more fumes in the beaker. Maintain this stage until most of the perchloric acid has evaporated, but avoid evaporation to dryness. Allow the solution to cool, the
44、n add about25ml of hydrochloric acid(4.5). Agitate and heat gently to dissolve the soluble salts. Allow the precipitate to settle for several minutes, then rinse the walls of the beaker with about30ml of water. Continue immediately, in accordance with7.4.2. 7.4.1.2 Acid attack (Method2) Place the te
45、st portion(7.2) in a400ml low-form beaker and moisten with 5ml of water. NOTE 7For ores having fluorine contents greater than0,1% (m/m) or where the fluorine content is unknown,0,8g of boric acid(4.2) should be added to the beaker containing the test portion before the addition of5ml of water. Add50
46、ml of hydrochloric acid(4.4). Cover the beaker with a watch-glass and heat gently without boiling, until decomposition of the test portion is complete. Add1ml of nitric acid(4.11) and then25ml of perchloric acid(4.7). Add1ml of sulfuric acid(4.9) to prevent precipitation of titanium. Partially uncov
47、er the beaker and heat until dense white fumes of perchloric acid appear. Cover the beaker completely and continue heating until there are no more fumes in the beaker. Maintain this stage until most of the perchloric acid has evaporated, but avoid evaporation to dryness. Allow the solution to cool,
48、then add about25ml of hydrochloric acid(4.5). Agitate and heat gently to dissolve the soluble salts. Add about30ml of water, mix and collect the precipitate on a close-texture filter paper containing small pieces of filter paper or a small amount of filter pulp. Rinse the beaker with water, and rub
49、the walls of the beaker using a rubber-tipped glass rod. Wash the residue three or four times with hot hydrochloric acid(4.6) and finally with hot water, until free from acids. Discard the filtrate and washings (see note8). NOTE 8For sinters, the silica should be recovered from this filtrate and washings, by the following procedure: Add10ml of perchloric acid(4.7) and1ml of sulfuric acid(4.9) to the filtrate and washings, and heat until dense white fumes of perchloric acid appear. Cover the beaker comple
