1、BRITISH STANDARD BS7020-16: 1993 ISO9685: 1991 Analysis of iron ores Part 16: Method for the determination of nickel and/or chromium contents: flame atomic absorption spectrometric method UDC 553.31:543.422:546.74:546.76BS7020-16:1993 This British Standard, having been prepared under the directionof
2、 the Iron and Steel Standards Policy Committee, waspublished underthe authorityof the Standards Boardand comes into effect on 15 October1993 BSI07-1999 The following BSI references relate to the work on this standard: Committee reference ISM/58 Draft for comment89/47025DC ISBN 0 580 22298 5 Committe
3、es 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 Coopte
4、d members 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 CommentsBS7020-16:1993 BSI 07-1999 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 2 6 Sampling and samples 2 7 Procedure 2 8 Expression of results 4 9 Test report 6 Annex A (normative) Flowsheet of the procedure for the acceptance of analytical values for test samples 7 Annex B (informative) Deri
6、vation of repeatability and permissible tolerance equations 8 Annex C (informative) Precision data obtained by international analytical trials 8 Figure C.1 Least-squares fit of precision against X for nickel 8 Figure C.2 Least-squares fit of precision against X for chromium 9 Table B.1 Nickel and ch
7、romium contents of test samples 8 List of references Inside back coverBS7020-16:1993 ii BSI 07-1999 National foreword This Part of BS7020 has been prepared under the direction of the Iron and Steel Standards Policy Committee and is identical with ISO9685:1991 Iron ores Determination of nickel and/or
8、 chromium contents Flame atomic absorption spectrometric method, published by the International Organization for Standardization (ISO). 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
9、 conjunction with this standard. A related British Standard 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. Complian
10、ce with a British Standard does not of itself confer immunity from legal obligations. Cross-references International standard Corresponding British Standard ISO1042:1983 BS1792:1982 Specification for one-mark volumetric flasks (Identical) BS5660 Methods of sampling iron ores ISO3081:1986 Part1:1987
11、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 by manual means (Identical) ISO7764:1985 BS7020 Analysis of iron ores Part1:1988
12、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 to10, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had
13、 amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS7020-16:1993 BSI 07-1999 1 1 Scope This International Standard specifies a flame atomic absorption spectrometric method for the determination of nickel and/or chromium contents of iron ores. This meth
14、od is applicable to nickel and/or chromium contents between0,003% (m/m) and0,1% (m/m) 1)in natural iron ores, iron ore concentrates and agglomerates, including sinter products. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisi
15、ons 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 to investigate the possibility of applying the most recent editions of the standards
16、 indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 648:1977, Laboratory glassware 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
17、 ores Increment sampling and sample preparation Mechanical method. ISO 3083:1986, Iron ores Preparation of samples Manual method. ISO 7764:1985, Iron ores Preparation of predried test samples for chemical analysis. 3 Principle Decomposition of the test portion by treatment with hydrochloric and nitr
18、ic acids. Removal of the major portion of iron in the filtrate by extraction with4-methylpentan-2-one. Ignition of the insoluble residue, removal of silicon dioxide by evaporation with hydrofluoric and sulfuric acids. Fusion of the residue with a mixture of sodium carbonate and sodium tetraborate, f
19、ollowed by dissolution with hydrochloric acid. Combination with the main solution. Aspiration into the flame of an atomic absorption spectrometer using an air-acetylene burner for nickel and a dinitrogen oxide-acetylene burner for chromium. Comparison of the absorbance values obtained with those obt
20、ained from the calibration solutions. 4 Reagents During the analysis, use only reagents of recognized analytical grade, and only distilled water or water of equivalent purity. 4.1 Sodium carbonate (Na 2 CO 3 ), anhydrous powder. 4.2 Sodium tetraborate (Na 2 B 4 O 7 ), anhydrous powder. 4.3 Lithium t
21、etraborate (Li 2 B 4 O 7 ), anhydrous powder. 4.4 Hydrochloric acid, 1,16g/ml to1,19g/ml. 4.5 Hydrochloric acid, 1,16g/ml to1,19g/ml, diluted2+1. 4.6 Hydrochloric acid, 1,16g/ml to1,19g/ml, diluted1+1. 4.7 Hydrochloric acid, 1,16g/ml to1,19g/ml, diluted2+100. 4.8 Nitric acid, 1,4g/ml. 4.9 Nitric aci
22、d, 1,4g/ml, diluted1+1. 4.10 Hydrofluoric acid, 1,13g/ml,40%(m/m), or 1,19g/ml,48%(m/m). 4.11 Sulfuric acid, 1,84g/ml. 4.12 Sulfuric acid, 1,84g/ml, diluted1+1. 4.13 4-Methylpentan-2-one, (methyl isobutyl ketone, MIBK). 4.14 Nickel standard solution A, 1004gNi/ml. Dissolve0,1000g of nickel metal pur
23、ity99,9%(m/m) (see note1,4.18) in30ml of nitric acid(4.9). After cooling, transfer to a1000ml one-mark volumetric flask quantitatively, dilute to volume with water and mix. 4.15 Nickel standard solution B, 104gNi/ml. Transfer100,0ml of nickel standardsolution A(4.14) to a1000ml one-mark volumetric f
24、lask. Dilute to volume with water and mix. 4.16 Chromium standard solution A, 1004gCr/ml. Dissolve0,1000g of chromium metal purity99,9%(m/m) (see note1,4.18) in20ml of hydrochloric acid(4.6). After cooling, transfer to a1000ml one-mark volumetric flask quantitatively, dilute to volume with water and
25、 mix. 4.17 Chromium standard solution B, 104gCr/ml. Transfer100,0ml ofchromium standard solution A(4.16) to a1000ml one-mark volumetric flask. Dilute to volume with water and mix. 1) This method has not been tested on ores containing more than0,056% (m/m) of chromium. (See Annex B.)BS7020-16:1993 2
26、BSI 07-1999 4.18 Nickel and chromium mixture solution. Introduce into a200ml beaker,30ml of hydrochloric acid(4.6),0,2ml of sulfuric acid(4.12) and a mixture of0,8g of sodium carbonate(4.1) and0,4g of sodium tetraborate(4.2). Heat to remove carbon dioxide and cool. Using pipettes or burettes, add10,
27、0ml of nickel standard solution A(4.14) and10,0ml of chromium standard solution A(4.16). Transfer to a100ml one-mark volumetric flask, dilute to the mark with water and mix. NOTE 1The purity of the metals stated on the certificates does not generally take into account the presence of adsorbed gases
28、like oxygen, carbon monoxide, etc. 5 Apparatus Ordinary laboratory apparatus, including one-mark pipettes and one-mark volumetric flasks complying with the specifications of ISO648 and ISO1042, and 5.1 Platinum crucible, of minimum capacity25ml. 5.2 Muffle furnace 5.3 Atomic absorption spectrometer,
29、 equipped with an air-acetylene and a dinitrogen oxide-acetylene burner. The atomic absorption spectrometer used in this method will be satisfactory if it meets the following criteria: a) Minimum sensitivity the absorbance of the most concentrated calibration solution (see7.5.4) is at least0,3. b) G
30、raph linearity the slope of the calibration graph covering the top20% of the concentration range (expressed as a change in absorbance) is not less than0,7 of the value of the slope for the bottom20% of the concentration range determined in the same way. c) Minimum stability the standard deviation of
31、 the absorbance of the most concentrated calibration solution and that of the zero calibration solution, each being calculated from a sufficient number of repetitive measurements, are less than1,5% and0,5% respectively of the mean value of the absorbance of the most concentrated solution. NOTE 2The
32、use of a strip-chart recorder and/or digital readout device is recommended to evaluate criteriaa),b) andc) and for all subsequent measurements. NOTE 3Instrument parameters will vary with each instrument. The following parameters were successfully used in several laboratories and they can be used as
33、guidelines. Solutions were aspirated into an air-acetylene or a dinitrogen oxide-acetylene flame of a premix burner: 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
34、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 with significant contents of combined water or oxidizable compounds, use a particle size of minus1604m.
35、 NOTE 4A guideline on significant contents of combined water and oxidizable compounds is incorporated in ISO7764. NOTE 5Ensure that the sample has not been pulverized in a nickel/chromium pot. 6.2 Preparation of predried test samples Thoroughly mix the laboratory sample and, taking multiple incremen
36、ts, extract a test sample in such a way 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 w
37、ith 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 previous result(s). For this particular analytical method, this condition implies that the repetition of the procedure shall be carried
38、 out either by the same operator at a different time or by a different operator including, in both cases, appropriate recalibration. 7.2 Safety precautions WARNING Follow the manufacturers instructions for igniting and extinguishing the air-acetylene flame or the dinitrogen oxide-acetylene flame to
39、avoid possible explosion hazards. Wear tinted safety glasses whenever the burner is in operation. Ni Cr Hollow-cathode lamp, mA 10 10 Wavelength, nm 232,0 357,9 Air flow rate, l/min 10 Acetylene flow rate, l/min 2,5 5 Dinitrogen oxide flow rate, l/min . 10BS7020-16:1993 BSI 07-1999 3 7.3 Test portio
40、n Taking several increments, weigh, to the nearest0,0002g, approximately1g of the predried test sample obtained in accordance with6.2. NOTE 7The test portion should be taken and weighed quickly, in order to avoid reabsorption of moisture. 7.4 Blank test and check test In each run, one blank test and
41、 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 in6.2. NOTE 8The certified reference ma
42、terial 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 both cases no significant changes in the analytical procedure will become necessary. When the analysis is carried out on several samples at the same
43、 time, the blank value may be represented by one test, provided that the procedure is the same and the reagents used are from the same reagent bottles. 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 materi
44、al may be used. 7.5 Determination 7.5.1 Decomposition of the test portion Transfer the test portion(7.3) to a250ml tall-form beaker. Moisten with a few millilitres of water. Add25ml of hydrochloric acid(4.4), cover with a watch-glass, and heat for about1h on a hotplate adjusted to give a temperature
45、 of100 C in a test beaker containing a similar volume and depth of sulfuric acid(4.11). NOTE 9When the amount of insoluble residue is high, continue heating on a higher temperature zone of the hotplate without boiling the solution. NOTE 10After heating, the volume of the solution should have decreas
46、ed to about10ml. Add5ml of nitric acid(4.8) and0,2ml of sulfuric acid(4.12), digest for about15min and evaporate the solution almost to dryness. NOTE 11When the test sample contains a significant content of barium, the addition of sulfuric acid(4.12) should be omitted. NOTE 12Be sure to cover with a
47、 watch-glass, in order to prevent sublimation of chlorides. During evaporation, shift the glass slightly. Add20ml of hydrochloric acid(4.6), and heat to dissolve the salts. Cool, wash the watch-glass and the walls of the beaker, and filter the solution through a close-texture filter paper containing
48、 filter pulp(0,3g to0,4g dry mass) into a200ml beaker. Carefully remove all adhering particles with a rubber-tipped glass rod or piece of moistened filter paper, and transfer to the filter, washing the paper with warm hydrochloric acid(4.7) until it is visibly free from iron, and again wash the pape
49、r with three or four portions of warm water. Reserve the filtrate and washings in the200ml beaker as the main solution. Transfer the filter paper and residue to a platinum crucible(5.1). 7.5.2 Removal of iron Heat the main solution and evaporate almost to dryness. Dissolve the salts in15ml of hydrochloric acid(4.5) and transfer to a200ml separating funnel. Rinse the beaker with20ml of hydrochloric acid(4.5) and transfer the washings to the funnel. Add50ml of4-methylpentan-2-one(4.13) to the funnel and shake it f
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