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1、BRITISH STANDARD BS 6200-3.22.1: 1992 Sampling and analysis of iron, steel and other ferrous metals Part 3: Methods of analysis Section 3.22 Determination of nitrogen Subsection 3.22.1 Steel: volumetric method Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:36 GMT+00:00 2006, Uncontroll
2、ed Copy, (c) BSI BS 6200-3.22.1:1992 This British Standard, having been prepared under the direction of the Iron and Steel Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 June 1992 BSI 09-1999 The following BSI references relate to the
3、 work on this standard: Committee reference ISM/18 Draft for comment 91/46620 DC ISBN 0 580 20797 8 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 whi
4、ch the following bodies were represented: BCIRA British 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.DateComments Licensed Copy: sheffieldun sheffie
5、ldun, na, Wed Dec 06 15:08:36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.22.1:1992 BSI 09-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Principle1 3Reagents1 4Apparatus2 5Sampling2 6Procedure2 7Calculation and expression of results6 8Test report6 Figure 1
6、 Steam distillation apparatus3 Figure 2 Cation exchange column4 Table 1 Precision data7 Table 2 Predicted values of r and R7 Publication(s) referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.22.1:1992 ii B
7、SI 09-1999 Foreword This Subsection of BS 6200 has been prepared under the direction of the Iron and Steel Standards Policy Committee and supersedes method 1 for the determination of nitrogen in BSI Handbook No. 19, to which it is technically equivalent. BS 6200 is a multipart British Standard, cove
8、ring 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 Part 1. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for
9、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 cover, pages i and ii, pages 1 to 8, an inside back cover and a back cover. This standard has been updated
10、(see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.22.1:1992 BSI 09-19991 1 Scope This Subsection
11、of BS 6200 describes a volumetric method for the determination of nitrogen in steel. The method is applicable to nitrogen contents from 0.005 % (m/m) to 0.25 % (m/m) in all types of steel except those containing silicon nitride. NOTE 1Complete recovery of nitrogen cannot be obtained from steels cont
12、aining silicon nitride. This nitride has been found only in samples of silicon steels manufactured without aluminium additions, and then only in sheet material. NOTE 2The titles of the publications referred to in this Subsection of BS 6200 are listed on the inside back cover. 2 Principle After solut
13、ion of the test portion in hydrochloric acid the “acid soluble” and “insoluble” nitrogen are separated by means of a centrifuge and the insoluble residue is decomposed by fuming strongly with sulfuric acid. The “acid soluble” and “insoluble” nitrogen contents are recovered separately as ammonia by s
14、team distillation over sodium hydroxide and the determinations are completed volumetrically by titration with hydrochloric acid. The total nitrogen content is obtained from the sum of the two determinations. NOTEThe terms “soluble” and “insoluble” nitrogen refer to chemical reactivity under the solv
15、ent conditions specified in this method, and do not necessarily imply metallurgical states. 3 Reagents During the analysis use only reagents of recognized analytical grade which are known to give a very low nitrogen blank. Use only grade 3 water as specified in BS 3978 except where ammonia-free wate
16、r is specifically stated. NOTEIf a solution requires filtration, wash the filter paper thoroughly with ammonia-free water before use. 3.1 Ammonia-free water. Prepare ammonia-free water by passing distilled water through the cation exchange column (4.4). It is essential to wash the resin column with
17、acid before use to convert it to the hydrogen form. This is conveniently performed by passing 2 l of hydrochloric acid (3.9) through the column, then washing with water until freed from acid. 3.2 Barium chloride solution, 100 g/l. Dissolve 10 g of barium chloride, BaCl2.2H2O, in ammonia-free water (
18、3.1), dilute to 100 ml with ammonia-free water and mix. 3.3 Boric acid solution, 1 g/l. Dissolve 1 g of boric acid in water, dilute to 1 l and mix. 3.4 Chromic-sulfuric acid. Dissolve 2 g of chromium(VI) oxide in 50 ml of water and add slowly and with constant stirring, 100 ml of sulfuric acid (3.16
19、). 3.5 Diphenylamine reagent. To 25 ml of water, add cautiously with stirring, 75 ml of sulfuric acid (3.16). Then add 0.1 g of diphenylamine, stir until dissolved and cool. 3.6 Disodium tetraborate, standard solution, 1 ml equivalent to 0.14 mg nitrogen. Dissolve 1.9072 g of freshly recrystallized
20、disodium tetraborate, Na2B4O7.10H2O, in 200 ml of water. Cool, transfer to a 1 l volumetric flask, dilute to the mark and mix. To prepare recrystallized disodium tetraborate, dissolve 15 g of the reagent in 50 ml of hot water. Cool. Filter the crystals under suction. Wash first with two 10 ml portio
21、ns of cold water, then with two 10 ml portions of 95 % ethanol, and finally with two 10 ml portions of diethyl ether. Spread the crystals on a clock glass and as soon as the ether has evaporated, transfer them to a weighing bottle and stopper tightly. 3.7 Hydrochloric acid, density = 1.16 g/ml to 1.
22、18 g/ml. 3.8 Hydrochloric acid, redistilled. To 300 ml of ammonia-free water (3.1) add 300 ml of hydrochloric acid (3.7) and distil in an all-glass distillation apparatus (4.6). Reject the first 100 ml of distillate and collect the next 400 ml for use. 3.9 Hydrochloric acid, = 1.16 g/ml to 1.18 g/ml
23、, diluted 1 + 9. 3.10 Hydrochloric acid, 0.01 M, approximately. Transfer 9.0 ml of hydrochloric acid (3.7) by means of a burette to a 1 l volumetric flask, dilute to the mark and mix. Transfer 100 ml of this solution to a second 1 l volumetric flask, dilute to the mark and mix. 3.11 Hydrofluoric aci
24、d, 40 % (m/m) approximately. 3.12 Hydrogen peroxide, approximately 6 g per 100 ml (20 volume). 3.13 Screened methyl red indicator. Dissolve 0.125 g of methyl red and 0.083 g of methylene blue in 100 ml of ethanol and mix. 3.14 Sodium hydroxide solution, 400 g/l. Dissolve 400 g of sodium hydroxide in
25、 ammonia-free water (3.1), dilute to 1 l with ammonia-free water (3.1) and mix. Prepare this solution in a polyethylene beaker with stirring and cooling. Store in a stoppered polyethylene bottle. 3.15 Sodium sulfate, anhydrous. 3.16 Sulfuric acid, = 1.84 g/ml. Test individual bottles of sulfuric aci
26、d and select one with a nitrogen content in any form of less than 0.5 g/g. Nitrogen as ammonia will usually be the major source of contamination, and this may be detected by normal methods. Nitrate may also be present and may be detected by the following procedure. Licensed Copy: sheffieldun sheffie
27、ldun, na, Wed Dec 06 15:08:36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.22.1:1992 2 BSI 09-1999 Cautiously add 6 ml of the sulfuric acid to 2 ml of water and cool to 60 C. Add one drop of hydrochloric acid (3.7) and one drop of diphenylamine reagent (3.5). No blue colour should develop. L
28、ess than 0.1 g/g can be detected by this test. 3.17 Sulfuric acid, diluted 1 + 4. To 400 ml of ammonia-free water (3.1) add cautiously, with cooling and stirring, 200 ml of sulfuric acid (3.16). Cool, dilute to 1 l with ammonia-free water (3.1) and mix. 4 Apparatus 4.1 Ordinary laboratory apparatus
29、4.2 Volumetric apparatus, in accordance with class A of BS 846, BS 1583 or BS 1792, as appropriate. 4.3 Steam distillation apparatus. The distillation unit illustrated in Figure 1 has been found to be suitable. NOTEApparatus assembled from units with standard tapered glass joints is NOT recommended.
30、 The joints may be attacked by the caustic solution and “freeze”. Flexibility is required to allow for the considerable vibration when the correct very rapid boil is used. Flask E is attacked by the sodium hydroxide solution and double-thickness glass is recommended. 4.4 Cation exchange column, pack
31、ed with a sulfonated polystyrene cation exchange resin. See Figure 2. 4.5 Centrifuge, electrically-driven, capable of attaining a measured speed of 3 000 r/min and with centrifuge tubes of at least 50 ml capacity. 4.6 Distillation apparatus, for purification of hydrochloric acid (3.8). 4.7 Burette,
32、of 10 ml capacity, with 0.02 ml graduations. NOTEA burette with double tap for connection to the storage bottle for hydrochloric acid (3.10) is convenient. A piston burette with certified precision has also been found to be satisfactory. 5 Sampling Carry out sampling in accordance with BS 1837. NOTE
33、BS 6200-2, which will supersede BS 1837, is currently in course of preparation. On its publication this Subsection will be amended to include sampling in accordance with BS 6200-2. 6 Procedure 6.1 Laboratory environment Carry out nitrogen determinations in a laboratory reserved for the purpose. It i
34、s particularly important to exclude ammonium salts and ammonia fumes. Reserve the glassware exclusively for this work. Clean the glassware with chromic-sulfuric acid solution (3.4) and wash thoroughly with ammonia-free water (3.1) before use. 6.2 Test portion Weigh, to the nearest 0.001 g, a test po
35、rtion of 3.5 g. For nitrogen contents greater than 0.04 % (m/m) reduce the mass of the test portion proportionately. For nitrogen contents greater than 0.03 % (m/m), where separate values for “soluble” and insoluble nitrogen fractions are not required, weigh, to the nearest 0.001 g, a test portion o
36、f 1.4 g and follow the dissolution procedure described in 6.6. 6.3 Blank test In parallel with the determination and following the same procedure, carry out a blank test using the same quantities of all reagents. NOTEThe combined blank values should not exceed 0.4 ml of hydrochloric acid (3.10), to
37、which the blank from the insoluble nitrogen determination should not contribute more than 0.25 ml. 6.4 Preparation of the steam distillation apparatus (4.3) 6.4.1 The detailed instructions in 6.4.2 refer to the electrically heated apparatus. If the steam generator is heated by gas, lower the tempera
38、ture during the syphoning of the sodium hydroxide solution, isolate the generator from flask C by a clip at position 3, and discharge the steam through funnel B. 6.4.2 Prepare the apparatus (see Figure 1) for use as follows. Add 3 l of ammonia-free water (3.1) to flask A. Remove the weighted stopper
39、 J, add 10 ml of sodium hydroxide solution (3.14) to flask E through funnel D and rinse in with ammonia-free water (3.1). With clips 1 and 2 open and stopper J removed, heat the water in flask A to boiling and allow steam to escape through funnel B. Close clip 1 and allow steam to escape from the op
40、en drain tube of flask C for approximately 1 min. Transfer three drops of screened methyl red indicator (3.13) and 10 ml of boric acid solution (3.3) to the 250 ml conical beaker G. Add hydrochloric acid (3.10) dropwise to the change point of the indicator. Place beaker G under the condenser F and r
41、aise until the condenser tip is immersed in the neutralized boric acid solution. Close clip 2, replace stopper J, and allow steam to pass through flask E into condenser F until approximately 60 ml of distillate has collected. This should take 5 min to 6 min. Lower the beaker until the condenser tip
42、is uncovered, then collect a further 10 ml of distillate. Rinse down the condenser tip with water and titrate the distillate with hydrochloric acid (3.10). Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.22.1:1992 BSI 09-19993 NOTE
43、This apparatus may be heated electrically by means of a 1 500 W immersion heater or alternatively by means of gas. Figure 1 Steam distillation apparatus Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:36 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6200-3.22.1:1992 4 BSI 09-1999 If the
44、 titration is greater than 0.1 ml, repeat the procedure. Collect a second 70 ml of distillate and titrate. If the titration still exceeds 0.1 ml a source of contamination is indicated. Do not make determinations until the source has been ascertained and eliminated. Switch off the heat to the boiling
45、 flask A. When the solution in flask E has syphoned into trap C, open clip 2 and discharge into the waste receiver H. NOTEAll linear dimensions are in millimetres. Figure 2 Cation exchange column Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 15:08:36 GMT+00:00 2006, Uncontrolled Copy, (c) B
46、SI BS 6200-3.22.1:1992 BSI 09-19995 6.5 Determination 6.5.1 Preparation of the test solution Place the test portion in a 200 ml conical flask and add 30 ml of hydrochloric acid (3.8). Dissolve steels which are resistant to hydrochloric acid in 30 ml of sulfuric acid (3.17). Cover and heat until solv
47、ent action appears to have ceased. Add 2 ml of hydrogen peroxide (3.12) and evaporate to 20 ml. If silica separates, add 1 ml of hydrofluoric acid (3.11). 6.5.2 Centrifuge separation of insoluble nitrides Transfer the solution together with any insoluble residue to a centrifuge tube containing 1 ml
48、of barium chloride solution (3.2), rinsing the flask with ammonia-free water (3.1). Add 1 ml of sulfuric acid (3.17), mix by shaking the tube gently, place in the centrifuge (4.5) and centrifuge at 3 000 r/min until the supernatant liquid is clear. Without disturbing the residue, transfer the clear
49、solution to another 200 ml conical flask and reserve. Wash the insoluble residue twice by centrifuging with 20 ml of ammonia-free water (3.1) and combine the washings with the reserved solution. NOTE 1Transfer of the supernatant liquid is facilitated by the use of a syphon tube and suction line fitted to a 2-hole bung to fit the neck of the 200 ml flask. This solution contains ammonium salts equivalent to the nitrogen soluble in hydrochloric acid. Rinse the insoluble residue into the original conical flask with ammonia-free water (3.1), add 5 ml of s
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