1、BRITISH STANDARD BS 6200-3.11.1: 1991 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.11 Determination of cobalt Subsection 3.11.1 Steel and cast iron: spectrophotometric methodBS 6200-3.11.1:1991 This British Standard, having been prepared under t
2、he directionof the Iron and Steel Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 20December 1991 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference ISM/18 Draft for comment 91/38343 DC ISBN 0 5
3、80 20223 2 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 Committee ISM/18, upon which the following bodies were represented: BCIRA British Steel Industry Department of Trad
4、e and Industry (Laboratory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No. Date CommentsBS 6200-3.11.1:1991 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principl
5、e 1 3 Reagents 1 4 Apparatus 1 5 Sampling 1 6 Procedure 1 7 Calculation and expression of results 2 8 Test report 3 Table 1 Cobalt content, reagent (3.5) addition, and cell size 1 Table 2 Calibration data for optical path lengths, equivalent cobalt percentageby mass and additions of standard cobalt
6、solution (3.1) 2 Table 3 Precision data 3 Table 4 Values for inter-laboratory agreement (2.83Sb, P = 95 %) 3 Publication(s) referred to Inside back coverBS 6200-3.11.1:1991 ii BSI 09-1999 Foreword This Subsection of BS6200 has been prepared under the direction of the Iron and Steel Standards Policy
7、Committee and supersedes method1 for the determination of cobalt in BSI Handbook No.19, to which it is technically equivalent. BS 6200 is a multipart British Standard, covering all aspects of the sampling and analysis of iron, steel and other ferrous metals. A list of contents, together with general
8、 information, is given in Part1. 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 obligations. Summary
9、of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 4, aninside 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 co
10、ver.BS 6200-3.11.1:1991 BSI 09-1999 1 1 Scope This Subsection of BS6200 describes a spectrophotometric method for the determination of cobalt in steel and cast iron. The method is applicable to cobalt contents from0.04% (m/m) to12% (m/m). NOTE 1Up to10% (m/m) vanadium and20% (m/m) tungsten do not in
11、terfere. NOTE 2The titles of the publications referred to in this Subsection of BS6200 are listed on the inside back cover. 2 Principle The test portion is dissolved in phosphoric-sulfuric acid mixture and oxidized with nitric acid. The reddish-brown coloured complex of cobalt with nitroso-R-salt is
12、 developed after adding sodium acetate as a buffer. Complexes from interfering elements are decomposed with nitric acid and the coloured cobalt complex is evaluated spectrophotometrically. 3 Reagents During the analysis, use only reagents of recognized analytical grades and only grade3 water as spec
13、ified in BS3978. 3.1 Cobalt standard solution, 1mg cobalt per millilitre. Dissolve1g of high purity cobalt sheet in20mL of nitric acid (3.4). Cool, transfer to a1L volumetric flask, dilute to the mark and mix. 3.2 Hydrochloric acid, density =1.16g/mL to1.18g/mL. 3.3 Iron, high purity, free from coba
14、lt. 3.4 Nitric acid, =1.42g/mL. 3.5 Nitroso-R-salt,3g/L solution. Dissolve0.3g of nitroso-R-salt (sodium1-nitroso-2-naphthol-3,6 disulfonate) in water. Dilute to100mL and mix. Make this solution immediately before use. 3.6 Phosphoric-sulfuric acid mixture. To600mL of water, add cautiously150mL of ph
15、osphoric acid, =1.75g/mL,150mL of sulfuric acid, =1.84g/mL, and mix. Cool, dilute to1L and mix. 3.7 Sodium acetate,500g/L solution. Dissolve500g of sodium acetate, CH 3 COONa.3H 2 O, in water, dilute to1L and mix. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance
16、with class A of BS846, BS1583 or BS1792, as appropriate. 4.3 Spectrophotometer, suitable for measuring absorbance at a wavelength of580nm. 4.4 Cells, having optical path lengths of4cm,2cm,1cm, and0.5cm. 5 Sampling Carry out sampling in accordance with BS1837. Prepare samples with cobalt-free cutting
17、 tools. NOTEBS 6200-2, which will supersede BS1837, is currently in preparation. On its publication this Subsection will be amended to include sampling in accordance with BS6200-2. 6 Procedure 6.1 Test portion For samples containing up to6% (m/m) cobalt, weigh to the nearest0.001g, a test portion of
18、0.5g. For higher contents up to12% (m/m) cobalt, weigh, to the nearest0.001g, a0.25g test portion and add0.25g of high purity iron (3.3). 6.2 Determination 6.2.1 Preparation of the test solution Place the test portion in a250mL conical beaker. Add20mL of phosphoric-sulfuric acid (3.6), cover the bea
19、ker and heat until solvent action ceases. Oxidize with nitric acid (3.4), and evaporate to fumes. If an acid-resistant carbide residue remains when solvent action ceases, add15mL of hydrochloric acid (3.2),5mL of nitric acid (3.4) and evaporate to fumes, then cool. Add20mL of water and repeat the ev
20、aporation to fumes. Cool, add50mL of water, heat until soluble salts are dissolved, and cool. Transfer to a100mL volumetric flask, dilute to the mark and mix. For samples containing large amounts of silica, graphite or niobium, filter through a dry filter paper into a dry flask, discarding the first
21、 few millilitres of the filtrate. Transfer two10mL aliquots of the solution into separate100mL volumetric flasks. Make this transfer and all subsequent reagent additions by means of a safety pipette or burette. 6.2.2 Development of the colour To the first aliquot add nitroso-R-salt solution (3.5) in
22、 accordance with Table 1, and mix. Table 1 Cobalt content, reagent (3.5) addition, and cell size Expected cobalt level Reagent (3.5) addition Cell path level % (m/m) mL cm 0.04 to0.8 10 4 0.8 to 1.6 15 2 1.6 to 3.2 20 1 3.2 to12.8 30 0.5BS 6200-3.11.1:1991 2 BSI 09-1999 For samples containing more t
23、han5% (m/m) nickel add extra reagent (3.5) at the rate of1mL per additional1% (m/m) nickel. For samples containing more than2% (m/m) copper add extra reagent (3.5) at the rate of2mL per additional1% (m/m) copper. Add 10 mL of sodium acetate solution (3.7), mix and allow to stand for5min at room temp
24、erature. Add5mL of nitric acid (3.4) mix, allow to stand for a further5min. Dilute to the mark and mix. 6.2.3 Compensating solution To the second aliquot add10mL of sodium acetate solution (3.7),5mL of nitric acid (3.4), dilute to the mark and mix. 6.2.4 Spectrophotometric measurement Measure the ab
25、sorbance of each solution at a wavelength of580nm, and at20 1 C, using a cell of appropriate path length for the cobalt concentration in accordance withTable 1. Use the same cell to measure the absorbance of the compensating solution6.2.3. Use the same cell also for the calibration procedure in6.3.
26、NOTEThe interference from vanadium at the wavelength of maximum absorption,525nm, is reduced by making the absorbance measurements at the580nm wavelength specified. Record the absorbance readings. 6.3 Preparation of the calibration graph Weigh nine 0.5 g portions of high purity iron (3.3) and place
27、in separate250mL conical beakers. Make additions of the standard cobalt solution (3.1) as given inTable 2, and according to the concentration of cobalt expected. Treat the calibration solutions exactly as described in6.2. Prepare separate calibration graphs by plotting the differences of the absorba
28、nce readings of the cobalt standard solutions and the zero cobalt solution against the equivalent cobalt percentage by mass for each calibration range. 7 Calculation and expression of results 7.1 Calculation From the difference in absorbance of the test solution and its compensating solution, read t
29、he cobalt percentage by mass from the calibration graph corresponding to the path length of the cell used. For an initial sample portion of0.25g, multiply the equivalent cobalt concentration derived from the graph by two. 7.2 Precision 7.2.1 Precision data Planned trials of this method were carried
30、out by nine to11 analysts each from a different laboratory and using seven steels. The mean results for each laboratory given in the original report 1) , have been examined statistically to obtain values for between-laboratory standard deviation, Sb. In the absence of individual results it is not po
31、ssible to calculate repeatability, r, and reproducibility, R, as defined in BS5497-1:1987. From the results reported 1) , for probability P =95%, the statistical limits (2.83Sb) for agreement between laboratory means have been calculated, and are given inTable 3. Table 2 Calibration data for optical
32、 path lengths, equivalent cobalt percentage by mass and additions of standard cobalt solution (3.1) 1) Methods of Analysis Committee. Absorptiometric determination of cobalt in iron and steel. Journal of the Iron and Steel Institute, January1954,176,5366. 4 cm cell 2 cm cell 1 cm cell 0.5 cm cell Co
33、balt solution Cobalt equivalent Cobalt solution Cobalt equivalent Cobalt solution Cobalt equivalent Cobalt solution Cobalt equivalent mL % (m/m) mL % (m/m) mL % (m/m) mL % (m/m) 0.0 nil 0.0 nil 0.0 nil 0.0 nil 0.5 0.1 1.0 0.2 2.0 0.4 4.0 0.8 1.0 0.2 2.0 0.4 4.0 0.8 8.0 1.6 1.5 0.3 3.0 0.6 6.0 1.2 12
34、.0 2.4 2.0 0.4 4.0 0.8 8.0 1.6 16.0 3.2 2.5 0.5 5.0 1.0 10.0 2.0 20.0 4.0 3.0 0.6 6.0 1.2 12.0 2.4 24.0 4.8 3.5 0.7 7.0 1.4 14.0 2.8 28.0 5.6 4.0 0.8 8.0 1.6 16.0 3.2 32.0 6.4BS 6200-3.11.1:1991 BSI 09-1999 3 Table 3 Precision data The difference between the mean results of two laboratories found on
35、 identical test material will exceed the95% probability level not more than once in20cases, on average, in the normal and correct operation of the method. 7.2.2 Regression data Statistical analysis of the results showed an approximately linear relationship between cobalt content and the value of the
36、 standard deviation of the laboratory means summarized by the following equation: standard deviation of laboratory mean, Sb =0.0135 Co% (m/m)+0.0054 The predicted values for the statistical limits of agreement between laboratory means at probability P =95% calculated from this equation are given inT
37、able 4. Table 4 Values for inter-laboratory agreement (2.83Sb, P = 95 %) 8 Test report The test report shall include the following information: a) all information necessary for the identification of the sample, the laboratory and the date of analysis; b) the method used, by reference to this Subsect
38、ion of BS6200; c) the results, and the form in which they are expressed; d) any unusual features noted during the determination; e) any operation not specified in this British Standard or any optional operation which may have influenced the results. Alloy type: element Cobalt content Between- labora
39、tory agreement 2.83Sb C Cr W V Mo Ni % (m/m) % (m/m) % (m/m) % (m/m) % (m/m) % (m/m) % (m/m) 40.0 0.31 0.067 0.9 4.6 6.7 1.4 4.2 0.675 0.047 1.3 12.0 0.8 1.03 0.065 2.2 18.8 2.0 2.15 2.89 0.103 1.4 13.0 0.7 2.0 3.97 0.190 0.8 4.3 19.0 1.0 0.8 5.45 0.115 0.8 4.5 18.0 1.5 1.0 10.62 0.47 Cobalt 2.83Sb
40、% (m/m) 0 0.015 0.1 0.019 0.2 0.023 0.5 0.034 1.0 0.053 2.0 0.092 5.0 0.206 10.0 0.3964 blankBS 6200-3.11.1:1991 BSI 09-1999 Publication(s) referred to BS 846, Specification for burettes. BS 1583, Specification for one-mark pipettes. BS 1792, Specification for one-mark volumetric flasks. BS 1837, Me
41、thods for the sampling of iron, steel, permanent magnet alloys and ferro-alloys. BS 3978, Specification for water for laboratory use. BS 5497, Precision of test methods. BS 5497-1, Guide for the determination of repeatability and reproducibility for a standard test method by inter-laboratory tests.
42、BS 6200, Sampling and analysis of iron, steel and other ferrous metals. BS 6200-1, Introduction and contents 2) . BS 6200-2, Methods of sampling and sample preparation 3) . BSI Handbook No.19, Methods for the sampling and analysis of iron, steel and other ferrous metals 2) . 2) Referred to in the fo
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