1、BRITISH STANDARD BS 6200-3.11.2: 1991 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.11 Determination of cobalt Subsection 3.11.2 Steel, irons and steelmaking materials: spectrophotometric method for trace amountsBS 6200-3.11.2:1991 This British S
2、tandard, having been prepared under the 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 D
3、raft for comment 91/38344 DC ISBN 0 580 20228 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 Committee ISM/18, upon which the following bodies were represented: BCIRA Brit
4、ish Steel Industry Department of Trade and Industry (Laboratory of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No. Date CommentsBS 6200-3.11.2:1991 BSI 09-1999 i Contents Page Committees responsible Inside front c
5、over Foreword ii 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Sampling 1 6 Procedure 1 7 Calculation and expression of results 3 8 Test report 4 Appendix A Application to steelmaking materials 5 Table 1 Calibration data for optical path lengths, additions of cobalt solution(3.2)and equivalen
6、t cobalt percentage by mass 3 Table 2 Precision data from steels and irons 3 Table 3 Regression data for steels and irons: values for inter-laboratory agreement (2.83Sb, P = 95%) 4 Table 4 Precision data from steelmaking materials 5 Table 5 Regression data for steelmaking materials: values for inter
7、-laboratoryagreement (2.83Sb, P = 95 %) 5 Publication(s) referred to Inside back coverBS 6200-3.11.2:1991 ii BSI 09-1999 Foreword This Subsection of BS 6200 has been prepared under the direction of the Iron and Steel Standards Policy Committee and supersedes method2 for the determination of cobalt i
8、n 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 information, is given in Part1. A British Standard does not purpo
9、rt 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 of pages This document comprises a front cover, an inside front co
10、ver, pages i and ii, pages1 to 6, an inside 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.BS 6200-3.11.2:1991 BSI 09-1999 1 1 Scope This Subsection of
11、BS 6200 describes a spectrophotometric method for the determination of trace amounts of cobalt in steel, iron, and steelmaking materials. The method is applicable to cobalt contents from0.002% (m/m) to0.04% (m/m). NOTEThe titles of the publications referred to in this Subsection of BS6200 are listed
12、 on the inside back cover. 2 Principle The test portion is dissolved in hydrochloric acid and oxidized with nitric acid. Iron and chromium are removed with zinc oxide. Cobalt is separated from nickel using 1-nitroso-2-naphthol, with a small addition of iron as a carrier. After ignition, the residue
13、is dissolved in acid and the reddish-brown coloured complex of cobalt with nitroso-R-salt is developed in a phosphoric-sulfuric acid solution buffered with sodium acetate. Complexes of interfering elements are decomposed with nitric acid and the cobalt complex is evaluated spectrophotometrically. 3
14、Reagents During the analysis, use only reagents of recognized analytical grades and only grade 3 water as specified in BS3978. 3.1 Cobalt standard solution, 1 mg cobalt per millilitre. Dissolve 1g of high purity cobalt sheet in20mL of nitric acid(3.6). Cool, transfer to a1L volumetric flask, dilute
15、to the mark and mix. 3.2 Cobalt standard solution, 0.025 mg cobalt per millilitre. By means of a pipette, transfer25mL of cobalt solution(3.1) to a1L volumetric flask, dilute to the mark and mix. 3.3 Hydrochloric acid, density = 1.16 g/mL to1.18g/mL. 3.4 Hydrochloric acid, = 1.16 g/mL to 1.18g/mL, d
16、iluted1 + 9. 3.5 Iron(III) chloride solution, 5mg iron per millilitre. Dissolve0.5g of high purity iron free from cobalt in20mL of hydrochloric acid(3.3), heat to boiling, oxidize with the minimum amount of nitric acid(3.6), and continue boiling to expel nitrous fumes. Cool, dilute to100mL and mix.
17、3.6 Nitric acid, = 1.42g/mL. 3.7 Nitric acid, = 1.42 g/mL, diluted 1 + 1. To50mL of water add 50mL of nitric acid(3.6) and mix. 3.8 1-nitroso-2-naphthol solution. Dissolve7g of1-nitroso-2-naphthol in 100mL of acetic acid, = 1.049g/mL. Prepare this solution immediately before use. 3.9 Nitroso-R-salt,
18、 3g/L solution. Dissolve0.3 g of nitroso-R-salt, (sodium 1-nitroso-2-naphthol-3,6 disulfonate), in water, dilute to100mL and mix. Prepare this solution immediately before use. 3.10 Perchloric acid, = 1.54g/mL. 3.11 Phosphoric-sulfuric acid mixture. To 600 mL of water, add cautiously 150 mL of phosph
19、oric acid, = 1.75g/mL, 150mL of sulfuric acid = 1.84g/mL, and mix. Cool, dilute to1L and mix. 3.12 Sodium acetate, 500 g/L solution. Dissolve500g of sodium acetate, CH 3 COONa.3H 2 O, in water, dilute to1L and mix. 3.13 Sulfuric acid, = 1.84g/mL, diluted 1 + 1. To400mL of water, add cautiously,500mL
20、 of sulfuric acid = 1.84g/mL, with cooling and stirring. Cool, dilute to1L and mix. 3.14 Sulfurous acid. Pass sulfur dioxide gas into1L of water until a saturated solution is obtained. 3.15 Zinc oxide suspension. To 200 mL of water, add50g of finely powdered zinc oxide, and stir or shake until a smo
21、oth cream is obtained. Stir the suspension immediately before use, and also between additions during use. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with classA of BS846, BS1583 or BS1792, as appropriate. 4.3 Spectrophotometer, suitable for measuring absorb
22、ance at a wavelength of525nm. 4.4 Cells, having optical path lengths of 4cm or 2cm. 5 Sampling Carry out sampling in accordance with BS 1837. Prepare samples with cobalt-free cutting tools. NOTEBS 6200-2, which will supersede BS1837, is currently in preparation. On its publication this Subsection wi
23、ll be amended to include sampling in accordance with BS 6200-2. 6 Procedure 6.1 Test portion Weigh, to the nearest0.001g, a test portion of2.5g. 6.2 Blank test In parallel with the determination and following the same procedure, carry out a blank test using the same quantities of reagents. NOTEThe b
24、lank is usually less than 0.0005% (m/m) cobalt.BS 6200-3.11.2:1991 2 BSI 09-1999 6.3 Determination 6.3.1 Preparation of the test solution NOTESee Appendix A for modifications to this procedure for particular steelmaking materials. Place the test portion in a650mL conical beaker. Add20mL of hydrochlo
25、ric acid(3.3), cover the beaker and heat until solvent action ceases. Oxidize with nitric acid(3.6). For high chromium steels only (for example more than10% (m/m) chromium) follow the procedure described in6.3.2. Evaporate to approximately10mL, add 30mL of water, cool, and dilute to approximately 30
26、0mL. 6.3.2 Removal of chromium Boil to remove nitrous fume and add 30 mL of perchloric acid(3.10). Evaporate to fumes and continue fuming until the chromium is oxidized. Add dropwise approximately1mL of hydrochloric acid(3.3), then reheat until the residual chromium is re-oxidized. Repeat the treatm
27、ent with hydrochloric acid followed by intermediate heating to fuming three or four times until most of the chromium has been volatilized. Cool, add 50mL of water and heat to dissolve salts, and add a few drops of sulfurous acid(3.14) to reduce residual chromate. Boil to remove excess of sulfur diox
28、ide, add 1 mL of nitric acid(3.6), and boil again to re-oxidize any reduced iron. Cool and dilute to approximately300mL. Continue as described in6.3.3. 6.3.3 Zinc oxide separation of iron Add zinc oxide suspension(3.15) about5mL at a time, mixing thoroughly after each addition, until the solution is
29、 neutralized and a faint permanent precipitate of iron-group hydroxides is obtained; then make a final addition of10mL of zinc oxide suspension(3.15) to complete the precipitation. It is indicated by a definite change from a clear dark-coloured solution to a turbid brown solution due to the precipit
30、ation of hydroxides. The addition of 10 mL excess of zinc oxide suspension (3.15) causes the brown precipitate to appear lighter in colour and the supernatant liquid to assume a slightly milky white appearance. Transfer to a 500 mL volumetric flask and dilute to the mark. Pour into a dry650mL conica
31、l beaker, mix and allow to stand for5min. Filter through a dry medium fast texture24cm fluted filter paper into a250mL volumetric flask. NOTEWhatman No. 12 or equivalent is suitable. Rinse the flask with the first few mL of the filtrate, and then collect a250mL aliquot. Transfer the aliquot to a650m
32、L conical beaker. 6.3.4 Separation of cobalt Add10mL of hydrochloric acid (3.3) and1mL of iron(III) chloride solution(3.5) and heat to boiling. Remove from the source of heat, add 15mL of1-nitroso-2-naphthol solution(3.8), stir in a little paper-pulp and allow to stand for at least3h, but preferably
33、 overnight. Filter through a paper-pulp pad, wash the pad and precipitate three times with hydrochloric acid(3.4), and then three times with cold water. Transfer the filter and precipitate to a platinum dish. Ignite at a low temperature until freed from carbonaceous matter and finally at a temperatu
34、re not exceeding800 C. Dissolve the residue in10mL of hydrochloric acid(3.3), add5mL of phosphoric-sulfuric acid(3.11), and evaporate to fuming. Cool, dissolve in5mL of water, transfer to a25mL volumetric flask, dilute to the mark and mix. 6.3.5 Development of the colour Transfer two 10 mL aliquots
35、of the solution into separate50mL volumetric flasks. Make this transfer and all subsequent reagent additions by means of a safety pipette or burette. To the first aliquot add10mL nitroso-R-salt solution(3.9) and mix. Add10mL of sodium acetate solution(3.12), mix and allow to stand for5 min at room t
36、emperature. Add10mL of nitric acid(3.7) mix, dilute to the mark and mix. Allow to stand for a further5min at room temperature. 6.3.6 Compensating solution To the second aliquot add 10 ml of sodium acetate solution(3.12), 10mL of nitric acid(3.7), dilute to the mark and mix. 6.3.7 Spectrophotometric
37、measurement Measure the absorbance of the test portion and blank solution at a wavelength of525nm, and at20 1 C, using cells of2cm or 4cm optical path length in accordance with the cobalt content and calibration graph described in6.4. Record the absorbance readings. 6.4 Preparation of the calibratio
38、n graph To a series of 250mL conical beakers add 1mL of iron(III) chloride solution(3.5) and 5mL of phosphoric-sulfuric acid mixture(3.11). Make additions of the standard cobalt solution(3.2) as given inTable 1, and according to the concentration of cobalt expected.BS 6200-3.11.2:1991 BSI 09-1999 3
39、Table 1 Calibration data for optical path lengths, additions of cobalt solution(3.2) and equivalent cobalt percentage by mass Evaporate to fuming. Cool, dissolve in5mL of water, transfer to a25mL volumetric flask, dilute to the mark and mix. Treat the calibration solutions exactly as described in6.3
40、.5 to6.3.7. Prepare calibration graphs by plotting the differences of the absorbance readings of the cobalt standard solutions and the zero cobalt solution against the equivalent cobalt percentage by mass. 7 Calculation and expression of results 7.1 Calculation From the difference in absorbance of t
41、he test solution and its compensating solution, read the cobalt percentage by mass from the calibration graph corresponding to the optical path length of the cell used. If necessary, subtract a cobalt blank correction determined from the absorbance readings obtained from the blank solution and its c
42、ompensating solution. 7.2 Precision 7.2.1 Precision data Planned trials of this method were carried out by nine to11 analysts, each from a different laboratory and using11 steels. The mean results for each laboratory given in the original report 1) , have been examined statistically to obtain values
43、 for between- laboratory standard deviation Sb. In the absence of individual results it is not possible to calculate repeatability r, and reproducibility R, as defined in BS 5497-1:1987. From the results reported, the statistical limits (2.83Sb) for probability P = 95%, for agreement between laborat
44、ory means have been calculated, and are given inTable 2. The difference between the mean results of two laboratories found on identical test material will exceed the95% probability level not more than once in20cases, on average, in the normal and correct operation of the method. Table 2 Precision da
45、ta from steels and irons 4 cm cell 2 cm cell Cobalt solution Cobalt equivalent Cobalt solution Cobalt equivalent mL % (m/m) mL % (m/m) 0.0 nil 0.0 nil 2.5 0.005 12.5 0.025 5.0 0.010 15.0 0.030 7.5 0.015 17.5 0.035 10.0 0.020 20.0 0.040 22.5 0.045 1) Methods of Analysis Committee. The absorptiometric
46、 determination of trace amounts of cobalt in iron and steel and some associated materials. Journal of the Iron and Steel Institute, March 1959, 191, 236-240. Alloy type: element Cobalt content Inter-laboratory agreement 2.83Sb C Si Mn Cr V Mo Ni Cu % (m/m) % (m/m) % (m/m) % (m/m) % (m/m) % (m/m) % (
47、m/m) % (m/m) % (m/m) 0.0002 0.0004 0.0002 0.0001 0.001 18.0 8.0 0.0030 0.00142 0.02 0.43 0.01 0.02 0.02 0.02 0.0033 0.00074 0.34 0.0115 0.00139 0.23 0.30 0.47 0.04 0.005 0.19 0.01 0.01 0.0125 0.00184 0.35 0.32 0.50 1.01 0.21 1.49 0.0170 0.00314 0.04 0.6 0.75 21.0 0.24 0.0265 0.00200 0.19 0.19 0.48 0
48、.10 0.05 0.01 0.18 0.12 0.0266 0.00303 0.15 0.19 0.48 0.08 0.04 0.04 0.03 0.06 0.0207 0.00286 0.13 1.21 2.34 0.36 0.18 0.0308 0.00311 0.25 0.02 0.20 0.46 0.01 4.10 0.11 0.0396 0.00405BS 6200-3.11.2:1991 4 BSI 09-1999 7.2.2 Regression data Statistical analysis of the results showed an approximately l
49、inear relationship between cobalt content and the value of the standard deviation of the laboratory means, summarized by the following equation: standard deviation of laboratory mean, Sb = 0.0267 Co% (m/m) + 0.00032 correlation = 0.874 The predicted values for the statistical limits of agreement between laboratory means at probability P = 95% calculated from this equation are given inTable 3. Table 3 Regression data for steels and irons: values for inter-laboratory agreeme
