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1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 1902-9.3:1998 ICS 81.0
2、80 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Methods of testing refractory materials Part 9. Chemical analysis by instrumental methods Section 9.3 Determination of chromium (VI) Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 08:19:38 GMT+00:00 2006, Uncontrolled
3、Copy, (c) BSI This British Standard, having been prepared under the direction of the Sector Board for Materials and Chemicals, was published under the authority of the Standards Board and comes into effect on 15 November 1998 BSI 1998 The following BSI references relate to the work on this standard:
4、 Committee reference RPI/1/14 Draft for comment 95/122097 DC ISBN 0 580 29599 0 BS 1902-9.3:1998 Amendments issued since publication Amd. No.DateText affected Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee RPI/1, Refract
5、ory products and materials, to Subcommittee RPI/1/14, Chemical analysis of refractories and technical ceramics, upon which the following bodies were represented: British Ceramic Research Ltd. British Industrial Ceramic Manufacturers Association Bureau of Analysed Samples China Clay Association Minis
6、try of Defence Refractories Association of Great Britain UK Steel Association Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 08:19:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 1902-9.3:1998 BSI 1998i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Principle1 3A
7、pparatus1 4Reagents1 5Sampling1 6Calibration1 7Procedure2 8Calculation of results2 9Test report2 Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 08:19:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii BSI 1998 BS 1902-9.3:1998 Foreword This section of BS 1902 has been prepared by Subcommittee
8、RPI/1/14, Chemical analysis of refractories and technical ceramics. Chromium (VI) is a listed hazardous material and current legislation requires that products and wastes are classified according to the chromium (VI) content. The method determines the chromium (VI) in a refractory so that it can be
9、assessed against legislative requirements. 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
10、. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 and 2, an inside back cover and a back cover. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 08:19:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 19981 BS 1902-9.3:1998 1 Scope This Br
11、itish Standard describes a method for the spectrometric determination of chromium (VI) in chrome-bearing refractories, before and after use. It can be applied to fired magnesia-chrome products (containing natural chromite, fused grain or co-clinker) and to unfired materials (with refractory cement o
12、r chemical bonds) although it may not be restricted to these types of refractory. The method is applicable to concentrations up to 500 mg/kg of chromium (VI). This range may be extended or reduced by modifying the dilution factors. 2 Principle Hexavalent chromium is extracted from the sample using a
13、 solution of 2 % NaOH/3 % Na2CO3which dissolves the common hexavalent chromium compounds potentially present (Ca, Fe, Na, K, Mg, Zn, Cu, Pb) but not their trivalent counterparts. The chromium (VI) is then determined spectrometrically by reaction with 1,5-diphenyl carbazide which forms a red-violet c
14、hromium complex. The absorbance of the complex is measured at a wavelength between 540 nm and 550 nm, the exact wavelength being given in the test report. NOTEIt is recognized that the method does not entail total dissolution of the test sample and hence not all the chromium (VI) may be taken into s
15、olution. Trials have indicated that the method yields a minimum of 80 % of the total chromium (VI) present and an inter-laboratory reproducibility of15 % of content. Should a more accurate assessment of chrome (VI) be required, repeat leachings can be carried out. 3 Apparatus 3.1 Analytical balance,
16、 capable of being read to0.0005 g. 3.2 Laboratory volumetric glassware, grade B or better. 3.3 Spectrophotometer, suitable for use in the 540 nm to 550 nm wavelength range. 3.4 Device for crushing bulk samples. 3.5 Device for fine grinding. 3.6 Magnet. 3.7 Hot plate magnetic stirrer. 4 Reagents 4.1
17、General Use only reagents of recognized analytical grade and only distilled or deionized water (electrical conductance less than 2 mV/cm). NOTECommercially available reagents with guaranteed concentrations may also be used. 4.2 Alkaline extraction solution Dissolve 30 g sodium carbonate (Na2CO3) and
18、 20 g sodium hydroxide pellets (NaOH) in water and dilute to volume in a 1 l volumetric flask. Mix thoroughly. 4.3 Chromium (VI) stock solution Weigh (0.3550.001) g of potassium dichromate (K2Cr2O7) dried at (11010) 8C and dissolve in approximately 200 ml of water in a 500 ml volumetric flask. Dilut
19、e to volume. This solution is stable indefinitely and contains 250 mg/l of chromium. 4.4 Chromium (VI) standard solution Using a pipette transfer 10 ml of the chromium (VI) stock solution (see 4.3) to a 500 ml volumetric flask and dilute to volume with water. NOTEDo not pipette by mouth. Prepare thi
20、s solution on the day of use. The solution contains 5 mg/l of chromium. 4.5 1,5-Diphenyl carbazide solution Dissolve 1 g of 1,5-diphenyl carbazide in 100 ml of propanone (acetone), (C3H6O). Acidify with one drop of glacial acetic acid. Prepare this solution on the day of use. 4.6 1+1 Sulfuric acid (
21、V/V) 5 Sampling Reduce the bulk sample by jaw crushing to a size suitable for fine grinding. Cone and quarter approximately 200 g of the crushed sample. Remove any iron introduced from the jaw crusher using a magnet. Fine grind the sample to reduce its particle size so that approximately 90 % is les
22、s than 125 mm. NOTE 1 Dust masks and skin protection should be worn and localized dust extraction used if possible during sample preparation. NOTE 2 Iron contamination from jaw crushing could potentially cause reduction of chromium (VI) during the analysis if not removed. NOTE 3 The removal of any m
23、etal or slag adhering to the sample by using a chisel or dry cutting is advisable, as their presence may result in the reduction of chromium (VI) during analysis. NOTE 4 Iron or steel mortars should not be used for fine grinding to avoid contamination of the sample by metallic iron. 6 Calibration To
24、 100 ml volumetric flasks, add 0 ml, 2 ml, 5 ml, 10 ml, 15 ml, 20 ml, and 25 ml of chromium (VI) standard solution (4.4). Add sufficient water to each flask to bring the volume to approximately 50 ml. Acidify each with 5 drops of sulfuric acid (4.6). Allow to cool. Add 10 ml of 1,5-diphenyl carbazid
25、e solution (4.5) and dilute to 100 ml. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 08:19:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 2 BSI 1998 BS 1902-9.3:1998 1)A Whatman No. 40 has been found suitable. Mix well and allow to stand for 5 min to 15 min for the colour to fully develop, a
26、nd measure within 30 min. Measure the absorbance between 540 nm and 550 nm against water in 10 mm glass cells. Plot absorbance against chromium (VI) concentration of the above solutions. The resulting graph will give a concentration range of 0 mg/kg to 500 mg/kg chromium (VI) when using the procedur
27、e described in clause 7. 7 Procedure Weigh (50.1) g of the fine ground sample to an accuracy of0.005 g after drying at (11010) 8C. Transfer into a 600 ml beaker and add 200 ml of the boiling alkaline extraction solution (4.2). Cover the beaker with a watch glass and boil with constant stirring for 3
28、0 min using a hot plate magnetic stirrer (to keep the sample in suspension). Do not allow it to evaporate to dryness. Allow to cool to ambient temperature. Filter the extract through a coarse filter paper1)pre-washed with cold extraction solution (4.2), into a 500 ml volumetric flask. Wash the resid
29、ue twice with 50 ml aliquots of the extraction solution (4.2) followed by water to a total volume of about 400 ml. Dilute to 500 ml with water. Pipette a 25 ml aliquot into a 250 ml beaker. Acidify by the dropwise addition of sulfuric acid (4.6), stirring until the evolution of carbon dioxide ceases
30、, then add a further five drops of sulfuric acid. Allow to cool to ambient temperature, then transfer to a 100 ml volumetric flask, add 10 ml of 1,5-diphenyl carbazide solution (4.5) and dilute to 100 ml. Allow the colour to develop for 5 min and measure the absorbance within 10 min at the wavelengt
31、h used for the calibration (see clause 6) using water in the reference cell and 10 mm glass cells. Do not allow to stand longer than 15 min as the colour of the solution can be affected. If the filtrate is discoloured or turbid, take another aliquot omitting the 1,5-diphenyl carbazide solution and m
32、easure its absorbance as a correction. Estimate the concentration of chromium (VI) from the calibration graph described in clause 6. NOTE 1 With high alumina materials, cloudiness may occur on acidification or after addition of 1,5-diphenyl carbazide solution. In the first case, the cloudiness may d
33、isappear after agitation and in the second, may be removed by the addition of a few further drops of sulfuric acid. NOTE 2 The range can be extended up to 1 250 mg/kg by using a 10 ml aliquot of extraction filtrate. NOTE 3 The presence of organic species in the test sample may interfere with the met
34、hod. 8 Calculation of results The calibration is for a range of 0 mg/kg to 500 mg/kg based on a 5 g sample and the method as described. Allowing for variation in sample mass and different aliquots being taken, the concentration of chromium (VI), in milligrams per kilogram (mg/kg), is given by the eq
35、uation: chromium (VI) = cVNMN vm where c is the concentration, as read off the graph, in milligrams per litre (mg/l); VNis the normal volume, in millilitres (ml); MNis the normal mass, in grams (g); v is the volume of aliquot taken, in millilitres (ml); m is the mass of sample used, in grams (g). Re
36、port the result to the nearest milligram per kilogram (mg/kg). 9 Test report The test report shall contain the following information: a) the name of the testing establishment; b) the date of the analysis; c) a reference to this method, e.g. determination of chromium (VI) in accordance with BS 1902-9
37、.3; d) the designation or description of the sample analysed; e) whether a single or duplicate determination was carried out; f) the wavelength used in the spectrophotometric determination; g) the result of the determination as concentration of chromium (VI) in mg/kg (see clause 8); h) any other fac
38、tors which may have influenced the result. Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 08:19:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI blank Licensed Copy: sheffieldun sheffieldun, na, Fri Nov 24 08:19:38 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 389 Chiswick High Road London W4
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