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1、BRITISH STANDARD BS 4267-7: 1987 Ammonium nitrate Part 7: Methods for determination of nitrite content NOTEIt is recommended that this Part of BS 4267 be read in conjunction with the information in the “General introduction”, published separately as BS 4267-0. WARNING. Ammonium nitrate is a strong o
2、xidizing agent. If necessary, break the test sample up by crushing rather than grinding. UDC 661.525:546.39175:543 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 08:19:28 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4267-7:1987 This British Standard, having been prepared under the direction
3、 of the Chemicals Standards Committee, was published under the authority of the Board of BSI and comes into effect on 30 September 1987 BSI 10-1999 The Committees responsible for this British Standard are shown in Part 0 The following BSI references relate to the work on this standard: Committee ref
4、erence CIC/21 Draft (ref. 86/53124) announced in BSI News, September 1986 ISBN 0 580 16120 X Foreword This Part of BS 4267 has been prepared under the direction of the Chemicals Standards Committee. It supersedes clause 9 of BS 4267:1968, to which it is technically equivalent and which has been dele
5、ted by amendment. This standard describes methods of test only, and should not be used or quoted as a specification defining limits of purity. Reference to this Part should indicate that the methods of test used are in accordance with BS 4267-7:1987. A British Standard does not purport to include al
6、l 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 cover, pages i and
7、 ii, pages 1 and 2, 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. Amendments issued since publication Amd. No.Date of issueComments Licensed
8、 Copy: sheffieldun sheffieldun, na, Fri Dec 01 08:19:28 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4267-7:1987 BSI 10-1999i Contents Page ForewordInside front cover 1Scope1 2Principle1 3Reagents1 4Apparatus1 5Procedure1 6Calculation and expression of results2 7Test report2 Publications referred t
9、oInside back cover Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 08:19:28 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 08:19:28 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4267-7:1987 BSI 10-19991 1 Scope This Part of BS 4267 d
10、escribes methods for determination of the nitrite content of ammonium nitrate for industrial use. The method is applicable to products with a nitrite content of not more than 5 mg/kg. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Principle Sul
11、phanilic acid is diazotized by the nitrite present in a test portion. The resulting diazo compound obtained is coupled with Cleves acid to give a magenta red colour which is measured spectrometrically or visually. 3 Reagents 3.1 General. During the analysis, use only reagents of recognized analytica
12、l grade and water complying with BS 3978. 3.2 Glacial acetic acid, = 1.05 g/mL. 3.3 Sulphanilic acid solution. Dissolve 0.5 g of sulphanilic acid in 120 mL of water and add 30 mL of the glacial acetic acid (3.2). 3.4 Cleves acid solution. Dissolve 0.2 g of Cleves acid in 120 mL of water warming to 4
13、0 C to aid solution. Filter the solution, cool, add 12 mL of the glacial acetic acid (3.2) and dilute to 150 mL with water. NOTEThe usual reagent available commercially is essentially 1-naphthylamine-7-sulphonic acid mixed with a smaller quantity of 1-naphthylamine-6-sulphonic acid. The latter has b
14、een found to be only half as sensitive as the former and it may be necessary to exercise some selection to obtain satisfactory sensitivity. 3.5 Sodium nitrite, standard solution, freshly prepared, using freshly boiled water. Dissolve 0.986 g of sodium nitrite, previously dried at 105 C, in water and
15、 dilute to 1 000 mL. Further dilute 5.0 mL of this solution to 1 000 mL. 1 mL of the second solution contains 1 4g of nitrite nitrogen. 4 Apparatus 4.1 Ordinary laboratory apparatus 4.2 Spectrometer, capable of measuring absorbance at a wavelength of approximately 525 nm and provided with cells of 1
16、0 mm optical path length. 4.3 Seven Nessler cylinders, complying with BS 612. 4.4 Nine 50 mL stoppered measuring cylinders, complying with BS 604. 5 Procedure 5.1 Test portion According to the expected nitrite content weigh, to the nearest 0.01 g, a test portion containing up to 15 4g of nitrite nit
17、rogen and, in any case, of mass not more than 25 g. 5.2 Calibration Prepare fresh calibration solutions as follows. Using one of the measuring cylinders (4.4) for each calibration solution, add successively 0.0, 3.0, 6.0, 9.0, 12.0 and 15.0 mL of the standard nitrite solution (3.5). Make up each mea
18、suring cylinder to about 40 mL with water, add 2 mL of the sulphanilic acid solution (3.3), mix thoroughly and allow to stand at 22 1 C for 20 min to 30 min. Add 5 mL of the Cleves acid solution (3.4), dilute to 50 mL with water, mix and allow to stand for a further 20 min to 30 min at 22 1 C. NOTET
19、he 0.0 mL calibration solution is the reagent blank. Using the spectrometer (4.2), measure the absorbance of each calibration solution at approximately 525 nm, with water as the reference. Subtract the absorbance value of the reagent blank from that of each calibration solution. Prepare a calibratio
20、n chart by plotting nitrite nitrogen (in 4g) against absorbance. 5.3 Determination 5.3.1 General. Carry out the determination at the same time as the procedure described in 5.2, following one of the methods described in 5.3.2 or 5.3.3. 5.3.2 Determination by spectrometer. Dissolve the test portion (
21、5.1) in a small amount of water and transfer into one of the measuring cylinders (4.4). Dilute the solution to 40 mL, add 2 mL of the sulphanilic acid solution (3.3), mix thoroughly and allow to stand at 22 1 C for 20 min to 30 min. Add 5 mL of the Cleves acid solution (3.4), dilute to 50 mL, mix an
22、d allow to stand for a further 20 min to 30 min at 22 C. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 08:19:28 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 4267-7:1987 2 BSI 10-1999 Using the spectrometer (4.2), measure the absorbance of this test solution at the wavelength used in the ca
23、libration and with water as the reference. Note the corresponding mass of nitrite nitrogen (in 4g) from the calibration chart. 5.3.3 Visual determination. Compare the colour of the test solution prepared (see 5.3.1) with the series of prepared colour standards (see 5.2) in matched Nessler cylinders.
24、 Note the nitrite content of the standard that most closely matches the test solution. 6 Calculation and expression of results 6.1 Determination by spectrometer Calculate the corrected absorbance from the following expression: A1 A2 where A1is the absorbance of the test solution (5.3.2) A2is the abs
25、orbance of the reagent blank (5.2). Using the corrected value of the absorbance, read the corresponding mass of nitrite from the calibration chart. The nitrite content, expressed as nitrite nitrogen, N, in mg/kg, is given by the following expression: where m1is the mass of nitrite nitrogen found (in
26、 4g); m0is the mass of the test portion (5.1) (in g). NOTETo convert the nitrite nitrogen content to ammonium nitrite content, multiply the value by a factor of 4.57. 6.2 Visual determination The nitrite content, expressed as nitrite nitrogen, N, in mg/kg, is given by the following expression: where
27、 7 Test report The test report shall include the following information: a) an identification of the sample; b) a reference to this British Standard, i.e. BS 4267-7:1987; c) the results expressed in accordance with 6.1 or 6.2; d) any unusual features noted during the determination; e) any operation n
28、ot included in this Part of BS 4267 or regarded as optional. m1 m0 - - m0is the mass of the test portion (5.1) (in g); m2is the mass of nitrite nitrogen in the closest matching calibration standard (5.3.3) (in g). m2 m0 - - Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 08:19:28 GMT+00:00 20
29、06, Uncontrolled Copy, (c) BSI BS 4267-7:1987 BSI 10-1999 Publications referred to BS 604, Specification for graduated glass measuring cylinders. BS 612, Specification for Nessler cylinders. BS 3978, Specification for water for laboratory use. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 0
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