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1、BRITISH STANDARD BS 7020-18: 1993 ISO 10204: 1992 Analysis of iron ores Part 18: Methods for the determination of magnesium content: flame atomic absorption spectrometric method UDC 553.31:543.22:546.46 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:54:01 GM
2、T+00:00 2006, Uncontrolled Copy, (c) BSI BS 7020-18:1993 This British Standard, having been prepared under the direction of the Iron and Steel Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 October 1993 BSI 07-1999 The following BSI r
3、eferences relate to the work on this standard: Committee reference ISM/58 Draft for comment 91/35110 DC ISBN 0 580 22299 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) to Technical Com
4、mittee ISM/58, upon which the following bodies were represented: British Steel Industry Institution of Mining and Metallurgy Coopted members The following body was also represented in the drafting of the standard, through subcommittees and panels: British Ceramic Research Ltd. Amendments issued sinc
5、e publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:54:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7020-18:1993 BSI 07-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Normative refe
6、rences1 3Principle1 4Reagents1 5Apparatus2 6Sampling and samples2 7Procedure2 8Expression of results4 9Test report5 Annex A (normative) Flowsheet of the procedure for the acceptance of analytical values for test samples6 Annex B (informative) Derivation of repeatability and permissible tolerance equ
7、ations7 Annex C (informative) Precision data obtained by international analytical trials7 Figure C.1 Least-squares fit of precision against X for magnesium7 Table 1 Dilution guide for test solution4 Table B.1 Magnesium contents of test samples7 List of referencesInside back cover Licensed Copy: Lond
8、on South Bank University, London South Bank University, Fri Dec 08 13:54:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7020-18:1993 ii BSI 07-1999 National foreword This Part of BS 7020 has been prepared under the direction of the Iron and Steel Standards Policy Committee and is identical with IS
9、O 10204:1992 Iron ores Determination of magnesium content Flame atomic absorption spectrometric method, published by the International Organization for Standardization (ISO). The Technical Committee has reviewed the provisions of ISO 648, to which normative reference is made in the text, and has dec
10、ided that they are acceptable for use in conjunction with this standard. A related British Standard to ISO 648:1977 is BS 1583:1986 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 responsib
11、le for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International standardCorresponding British Standard ISO 1042:1983BS 1792:1982 Specification for one-mark volumetric flasks (Identical) BS 5660 Methods of
12、sampling iron ores ISO 3081:1986Part 1:1987 Manual method of increment sampling (Identical) ISO 3082:1987Part 2:1987 Mechanical method of increment sampling and sample preparation (Identical) ISO 3083:1986BS 5661:1987 Method for preparation of samples of iron ores by manual means (Identical) ISO 776
13、4:1985BS 7020 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, pages i and ii, pages 1 to 8, an inside back cover and a back cover. This standard has
14、 been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:54:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7020-18:1
15、993 BSI 07-19991 1 Scope This International Standard specifies a flame atomic absorption spectrometric method for the determination of the magnesium content of iron ores. This method is applicable to magnesium contents between 0,01 % (m/m) and 3,0 % (m/m) in natural iron ores, iron ore concentrates
16、and agglomerates, including sinter products. 2 Normative references The following standards 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 revi
17、sion, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 648:1977, Laboratory gla
18、ssware One-mark pipettes. ISO 1042:1983, Laboratory glassware One-mark volumetric flasks. ISO 3081:1986, Iron ores Increment sampling Manual method. ISO 3082:1987, Iron ores Increment sampling and sample preparation Mechanical method. ISO 3083:1986, Iron ores Preparation of samples Manual method. IS
19、O 7764:1985, Iron ores Preparation of predried test samples for chemical analysis. 3 Principle Decomposition of the test portion by treatment with hydrochloric acid and a small amount of nitric acid. Evaporation to dehydrate silica, followed by dilution and filtration. Ignition of the residue and re
20、moval of silica by evaporation with hydrofluoric and sulfuric acids. Fusion with sodium carbonate and dissolution of the cooled melt in the filtrate. Aspiration of the solution obtained into the flame of an atomic absorption spectrometer using an air-acetylene burner. Comparison of the absorbance va
21、lues obtained for magnesium with those obtained from the calibration solutions. NOTE 1A dinitrogen oxide-acetylene flame may be used for the determination, in which case the sensitivity is decreased by a factor of about 3. 4 Reagents During the analysis, use only reagents of recognized analytical gr
22、ade and only distilled water or water of equivalent purity. 4.1 Sodium carbonate (Na2CO3), anhydrous. 4.2 Hydrochloric acid, 1,19 g/ml. 4.3 Hydrochloric acid, 1,19 g/ml, diluted 1 + 9. 4.4 Nitric acid, 1,4 g/ml. 4.5 Hydrofluoric acid, 1,13 g/ml, 40 % (m/m), or 1,185 g/ml, 48 % (m/m). 4.6 Sulfuric ac
23、id, 1,84 g/ml, diluted 1 + 1. 4.7 Background solution Dissolve 10 g of pure iron wire minimum purity 99,9 % (m/m), of magnesium content less than 0,0002 % (m/m) in 50 ml of hydrochloric acid (4.2) and oxidize by adding nitric acid (4.4) drop by drop. Evaporate until a syrupy consistency is obtained.
24、 Add 20 ml of hydrochloric acid (4.2) and dilute to 200 ml with water. Dissolve 17 g of sodium carbonate (4.1) in water, add carefully to the iron solution and heat to remove carbon dioxide. Transfer the cooled solution to a 1 000 ml one-mark volumetric flask, dilute to volume with water and mix. 4.
25、8 Lanthanum chloride solution Dissolve 50 g of lanthanum chloride (LaCl3.xH2O) of magnesium content less than 0,002 % (m/m) in 50 ml of hydrochloric acid (4.2) and 300 ml of hot water. Cool and dilute to 1 litre. 4.9 Magnesium standard solution, 15 4g Mg/ml. Dissolve 0,300 0 g of oxide-free magnesiu
26、m metal minimum purity 99,9 % (m/m) by slowly adding 75 ml of hydrochloric acid ( 1,19 g/ml), diluted 1 + 3. When dissolved, cool, transfer to a 1 000 ml one-mark volumetric flask, dilute to volume with water and mix. Transfer 10 ml of this solution to a 200 ml one-mark volumetric flask, dilute to v
27、olume with water and mix. 4.10 Magnesium calibration solutions. Using pipettes, transfer 2,0 ml; 5,0 ml; 10,0 ml; 20,0 ml; 40,0 ml; and 50,0 ml portions of the magnesium standard solutions (4.9) to 200 ml volumetric flasks (see note 2). Add 6 ml of hydrochloric acid (4.2), 60 ml of background soluti
28、on (4.7) and 40 ml of lanthanum chloride solution (4.8) to each flask. Dilute all the solutions to volume with water and mix. Prepare a zero magnesium calibration solution by transferring 60 ml of the background solution to a 200 ml volumetric flask, add 6 ml of hydrochloric acid (4.2) and 40 ml of
29、lanthanum chloride solution. Dilute all the solutions to volume with water and mix. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 13:54:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7020-18:1993 2 BSI 07-1999 NOTE 2The range of magnesium which can be covere
30、d may vary from instrument to instrument. Attention should be paid to the minimum criteria given in 5.3. For instruments having high sensitivity, smaller portions of standard solution or a more diluted standard solution can be used. 5 Apparatus Ordinary laboratory apparatus, including one-mark pipet
31、tes and one-mark volumetric flasks complying with the specifications of ISO 648 and ISO 1042 respectively, and 5.1 Platinum crucible, of minimum capacity 30 ml. 5.2 Muffle furnace, capable of maintaining a temperature of approximately 1 100 C. 5.3 Atomic absorption spectrometer, equipped with an air
32、-acetylene burner. The atomic absorption spectrometer used in this method shall meet the following criteria. a) Minimum sensitivity the absorbance of the most concentrated magnesium calibration solution (4.10) shall be at least 0,3. b) Graph linearity the slope of the calibration graph covering the
33、top 20 % of the concentration range (expressed as a change in absorbance) shall not be less than 0,7 of the value of the slope for the bottom 20 % of the concentration range determined in the same way. c) Minimum stability the standard deviation of the absorbance of the most concentrated calibration
34、 solution and that of the zero calibration solution, each being calculated from a sufficient number of repetitive measurements, shall be less than 1,5 % and 0,5 % respectively of the mean value of the absorbance of the most concentrated calibration solution. NOTE 3The use of a strip chart recorder a
35、nd/or digital readout device is recommended to evaluate criteria a) b) and c) and for all subsequent measurements. NOTE 4Instrument parameters may vary with each instrument. The following parameters were successfully used in several laboratories and they can be used as guidelines. An air-acetylene f
36、lame was used. In systems where the values shown above for gas flow rates do not apply, the ratio of the gas flow rates may still be a useful guideline. 6 Sampling and samples 6.1 Laboratory sample For analysis, use a laboratory sample of minus 100 4m particle size which has been taken in accordance
37、 with ISO 3081 or ISO 3082 and prepared in accordance with ISO 3082 or ISO 3083. In the case of ores having significant contents of combined water or oxidizable compounds, use a particle size of minus 160 4m. NOTE 5A guideline on significant contents of combined water and oxidizable compounds is inc
38、orporated in ISO 7764. 6.2 Preparation of predried test samples Thoroughly mix the laboratory sample and, taking multiple increments, extract a test sample in such a way that it is representative of the whole contents of the container. Dry the test sample at 105 C 2 C, as specified in ISO 7764. (Thi
39、s 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. NOTE 6The expression “independently” means that the second and any subsequent result is not affected by the pr
40、evious 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 or by a different operator including, in either case, appropriate recalibration. 7.2 Test portion Taking several increme
41、nts, weigh, to the nearest 0,000 2 g, approximately 1 g of the predried test sample obtained in accordance with 6.2. NOTE 7The test portion should be taken and 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
42、 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 in 6.2. NOTE 8The certified reference material should be of the sam
43、e 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 changes in the analytical procedure will become necessary. When the analysis is carried out on several samples at the same time, the blank value may
44、 be represented by one test, provided that the procedure is the same and the reagents used are from the same reagent bottles. Hollow cathode lamp, mA15 Wavelength, nm285,2 Air flow rate, l/min22 Acetylene flow rate, l/min4,2 Licensed Copy: London South Bank University, London South Bank University,
45、Fri Dec 08 13:54:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7020-18:1993 BSI 07-19993 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. 7.4 Determination 7.4.1 Decomposition of the
46、 test portion Transfer the test portion (7.2) to a 250 ml beaker. Moisten with a few millilitres of water, add 25 ml of hydrochloric acid (4.2), cover with a watch-glass and heat gently. Increase the heat and digest just below boiling, until no further attack is apparent. Add 2 ml of nitric acid (4.
47、4) and digest for several minutes. Remove the watch-glass and evaporate the solution to dryness. Heat the salts on a hot-plate at 105 C to 110 C for 30 min. Add 5 ml of hydrochloric acid (4.2), cover the beaker with a watch-glass, and warm for several minutes. Add 50 ml of water, stirring to avoid t
48、he hydrolysis of titanium, and heat to boiling. Wash the watch-glass and the walls of the beaker and filter the solution through a medium-texture paper containing some filter pulp into a 250 ml beaker. Carefully remove all adhering particles with a rubber-tipped glass rod or moistened filter paper a
49、nd transfer to the filter, washing three times with dilute hydrochloric acid (4.3), then with hot water until the filter paper is free of iron. Transfer the paper and residue to a platinum crucible (5.1). Evaporate the filtrate to about 100 ml and retain it. 7.4.2 Treatment of the residue Ignite the filter paper and residue in a platinum crucible (5.1) at a low temperature (500 C to 800 C). Cool, moisten with a few drops of water, add 3 or 4 drops of sulfuric acid (4.6) and 10 ml of hydrofluoric acid (4.5). Evaporate s