1、BRITISH STANDARD BS 6200-3.5.2: 1991 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.5 Determination of boron Subsection 3.5.2 Ferroboron: volumetric methodBS6200-3.5.2:1991 This British Standard, having been prepared under the directionof the Iron
2、 and Steel Standards Policy Committee, waspublished under the authorityof the Standards Boardand comes into effect on 20December1991 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference ISM/18 Draft for comment 91/38342 DC ISBN 0 580 20224 0 Committees re
3、sponsible 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 Trade and Industry (Laborato
4、ry of the Government Chemist) Ferro Alloys and Metals Producers Association Ministry of Defence Amendments issued since publication Amd. No. Date CommentsBS6200-3.5.2:1991 BSI 08-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparat
5、us 1 5 Sampling 1 6 Procedure 1 7 Calculation and expression of results 2 8 Test report 3 Table 1 Precision data 2 Publication(s) referred to Inside back coverBS6200-3.5.2:1991 ii BSI 08-1999 Foreword This Subsection of BS6200 has been prepared under the direction of the Iron and Steel Standards Pol
6、icy Committee and supersedes method2 for the determination of boron 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 gene
7、ral 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. Summa
8、ry of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 4, 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 fron
9、t cover.BS6200-3.5.2:1991 BSI 08-1999 1 1 Scope This Subsection of BS6200 describes a volumetric method for the determination of boron in ferroboron. The method is applicable to the range of boron content normally found in ferroboron. NOTEThe titles of the publications referred to in this Subsection
10、 of BS6200 are listed on the inside back cover. 2 Principle A solution of the test portion in sulfuric acid is passed through a column of cation exchange resin to remove iron and interfering impurities and boron is determined in the eluate after addition of mannitol by titration with sodium hydroxid
11、e. 3 Reagents During the analysis use only reagents of recognized analytical grade and only grade 3 water as specified in BS 3978. 3.1 Boric acid, standard solution, 0.6mg boron permillilitre. Dissolve3.429g of boric acid in water. Transfer to a 1 L volumetric flask, dilute to the mark and mix. 3.2
12、Hydrochloric acid, density = 1.16 g/mL to 1.18 g/mL, diluted1+1. 3.3 Hydrochloric acid, = 1.16 g/mL to 1.18g/mL, diluted 1+9. 3.4 Hydrochloric acid, = 1.16g/mL to 1.18g/mL, diluted1+99. 3.5 Mannitol 3.6 Mixed indicator. Dissolve0.05g of methyl red,0.1g of bromocresol green, 0.3g of phenolphthalein a
13、nd0.3g of thymol blue in100mL of methanol. 3.7 Nitric acid, = 1.42g/mL. 3.8 Sodium hydroxide, 100g/L solution. Dissolve100 g of sodium hydroxide cautiously, with stirring and cooling, in600mL of water, dilute to1L and mix. 3.9 Sodium hydroxide, 4g/L solution, 0.1M approximately. Dissolve4g of sodium
14、 hydroxide in water and cool. Transfer to 1 L volumetric flask, dilute to the mark and mix. Store in a a stoppered polyethylene bottle. 3.10 Sodium peroxide 3.11 Sulfuric acid, 1.84g/mL, diluted1+1. To400mL of water add, cautiously, 500mL of sulfuric acid, = 1.84g/mL, with stirring and cooling. Cool
15、, dilute to1L, and mix. 4 Apparatus IMPORTANT NOTE. Use only glassware which is known to give a low boron blank. 4.1 Ordinary laboratory apparatus 4.2 Volumetric glassware, in accordance with classA of BS846, BS1583 or BS1792, as appropriate. 4.3 Reflux air condenser, comprising a300mm 6mm diameter
16、glass tube with a ground-glass joint fitting to a250mL round-bottomed flask. 4.4 Cation exchange column, comprising a glass tube approximately300mm long 16mm diameter, packed with a suitable sulfonated polystyrene cation exchange resin, particle size0.3mm to1.18mm, (14mesh to52mesh). Wash the column
17、 with hydrochloric acid (3.2) when the resin is new, and also after every four determinations (to remove iron). Then wash with water until the washings are neutral. 4.5 pH meter, which may be used as an alternative to the mixed indicator (3.6). 5 Sampling Carry out sampling in accordance with BS1837
18、. Ferroboron is particularly prone to segregation because of the extended freezing range of the binary system; it is preferable to obtain the main sample when the melt is crushed. NOTEBS 6200-2, which will supersede BS1837, is currently in preparation. On its publication this Subsection will be amen
19、ded to include sampling in accordance with BS6200-2. 6 Procedure 6.1 Test portion Weigh, to the nearest0.001g, a test portion of1g. 6.2 Blank test In parallel with the determination and following the same procedure carry out a blank test using the same quantities of all reagents. 6.3 Preparation of
20、the test solution Place the test portion in a250mL round-bottomed flask (4.3) and add75mL of water, 5mL of sulfuric acid (3.11), and3.5 mL of nitric acid (3.7). Fit the reflux air condenser (4.3) and heat under gentle reflux until solvent action ceases. Continue to heat gently for a further30min. Co
21、ol, rinse and remove the condenser tube. Filter through a small paper-pulp pad into a500mL volumetric flask and wash with the minimum amount of hydrochloric acid(3.4). Reserve the solution in the500mL volumetric flask.BS6200-3.5.2:1991 2 BSI 08-1999 Transfer the filter to a platinum dish and ignite
22、at a low temperature until carbonaceous matter is destroyed. Cool, transfer the residue to a nickel or iron crucible and fuse with the minimum amount of sodium peroxide (3.10) (0.5g to 1.0g is usually sufficient). Use a small flame until the reaction subsides and finally heat at a bright red heat fo
23、r2min. Cool and extract the fusion products in water, filter to remove iron or nickel oxide and wash with water. Add the filtrate to the main solution in the500mL volumetric flask. Dilute to the mark and mix. 6.4 Separation of boron by ion exchange Transfer a50mL aliquot of the solution to the top o
24、f the prepared ion exchange column and pass the solution through the column at a rate of approximately5mL per min. Wash several times with water, using200mL to250mL of water in all. Collect the eluate and washings in a600mL conical flask. 6.5 Titration of the boron 6.5.1 Using mixed indicator Add ap
25、proximately 1 mL of mixed indicator (3.6) then sodium hydroxide solution (3.8) dropwise until a purple colour appears. Acidify with hydrochloric acid (3.3) dropwise from a burette to the appearance of a red colour, then add one drop in excess. Boil under a reflux condenser for 5 min and cool. Neutra
26、lize the excess acid by adding sodium hydroxide solution (3.9) dropwise from a burette to the appearance of a green colour. IMPORTANT NOTE. The sodium hydroxide used up to this point does not count in the titration. Add 20 g of mannitol (3.5) and titrate with sodium hydroxide solution (3.9) to the a
27、ppearance of a purple colour. Record the volume, V t , of sodium hydroxide solution used. Titrate the blank test, following the same procedure, and record the volume, V b , of sodiumhydroxide (3.9) solution used. 6.5.2 Using a pH meter Adjust the boron solution with sodium hydroxide solution (3.9),
28、using the pH meter (4.5), to pH 6. Add20 g of mannitol (3.5), and titrate with sodium hydroxide solution (3.9) topH8. Record the volume,V t , of sodium hydroxide solution used. Titrate the blank test, following the same procedure, and record the volume, V b , of sodium hydroxide solution (3.9) used.
29、 6.5.3 Standardization of the sodium hydroxide solution Transfer50mL of boric acid solution (3.1) to a600mL conical beaker and dilute to approximately 250 mL. Add a few drops of hydrochloric acid (3.3) and then continue using the same procedure, 6.5.1 or6.5.2, as used in the boron determination. Rec
30、ord the volume, V f , of sodium hydroxide solution (3.9) used. 7 Calculation and expression of results 7.1 Calculation Calculate c, the boron equivalent in milligrams per millilitre of the sodium hydroxide solution (3.9), from the equation: c = 30/V c where V cis the volume of sodium hydroxide solut
31、ion(3.9) used in 6.5.3 (in mL). Calculate the boron content, B, expressed as a percentage by mass, from the equation: B = c(V t V b ) where c is the equivalent concentration of boron of the sodium hydroxide solution (3.9) expressed as boron (in mg/mL); V tis the volume of sodium hydroxide solution(3
32、.9) used in the titration of the test portion (in mL); V bis the volume of sodium hydroxide solution(3.9) used in the titration of the blank test (in mL). 7.2 Precision A planned trial of this method was carried out by10analysts each from a different laboratory; three tests were carried out by each
33、analyst on each of two samples. From the results obtained, the95% confidence limits (2s) have been calculated in accordance with BS5497-1 and are given inTable 1. Table 1 Precision data The difference between two single results found on identical material by one analyst using the same apparatus with
34、in a short time interval will exceed the repeatability r, on average, not more than once in twenty cases in the normal and correct operation of the method. Boron Repeatability r Reproducibility R % (m/m) 15.4 0.170 0.48 19.3 0.206 0.41BS6200-3.5.2:1991 BSI 08-1999 3 The difference between two single
35、 and independent results found by two operators working in different laboratories on identical test material will exceed the reproducibility, R, on average, not more than once in 20 cases in the normal and correct operation of the method. 8 Test report The test report shall include the following inf
36、ormation: 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 Subsection of BS 6200; c) the results, and the form in which they are expressed; d) any unusual features noted during the determination; e) a
37、ny operation not specified in this British Standard or any optional operation which may have influenced the results.4 blankBS6200-3.5.2:1991 BSI 08-1999 Publication(s) referred to BS 846, Specification for burettes. BS 1583, Specification for one-mark pipettes. BS 1792, Specification for one-mark vo
38、lumetric flasks. BS 1837, Methods 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
39、 by inter-laboratory tests. BS 6200, Sampling and analysis of iron, steel and other ferrous metals. BS 6200-1, Introduction and contents 1) . BS 6200-2, Methods of sampling and sample preparation 2) . BSI Handbook No. 19 1)Methods for the sampling and analysis of iron, steel and other ferrous metals
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