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 661.525:546.39175:543BS4267-7:1987 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authorityofthe Board of BSIandcomes into effect
3、 on 30 September 1987 BSI 10-1999 The Committees responsible forthis British Standard are showninPart 0 The following BSI references relateto the work on this standard: Committee reference CIC/21 Draft (ref. 86/53124) announced inBSI News, September 1986 ISBN 0 580 16120 X Foreword This Part of BS 4
4、267 has been prepared under the direction of the Chemicals Standards Committee. It supersedes clause 9 of BS4267:1968, to which it is technically equivalent and which has been deleted by amendment. This standard describes methods of test only, and should not be used or quoted as a specification defi
5、ning limits of purity. Reference to this Part should indicate that the methods of test used are in accordance with BS4267-7:1987. 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. Compl
6、iance 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 and 2, an inside back cover and a back cover. This standard has been updated (see copyright date) and may ha
7、ve had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS4267-7:1987 BSI 10-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Proce
8、dure 1 6 Calculation and expression of results 2 7 Test report 2 Publications referred to Inside back coverii blankBS4267-7:1987 BSI 10-1999 1 1 Scope This Part of BS 4267 describes methods for determination of the nitrite content of ammonium nitrate for industrial use. The method is applicable to p
9、roducts with a nitrite content of not more than5mg/kg. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Principle Sulphanilic acid is diazotized by the nitrite present in a test portion. The resulting diazo compound obtained is coupled with Cleve
10、s 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 analytical grade and water complying with BS3978. 3.2 Glacial acetic acid, = 1.05 g/mL. 3.3 Sulphanilic acid solution. Dissolve 0.5 g of s
11、ulphanilic 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 40 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. NOTETh
12、e usual reagent available commercially is essentially1-naphthylamine-7-sulphonic acid mixed with a smaller quantity of 1-naphthylamine-6-sulphonic acid. The latter has been found to be only half as sensitive as the former and it may be necessary to exercise some selection to obtain satisfactory sens
13、itivity. 3.5 Sodium nitrite, standard solution, freshly prepared, using freshly boiled water. Dissolve0.986g of sodium nitrite, previously dried at 105 C, in water and dilute to 1000 mL. Further dilute 5.0 mL of this solution to 1000 mL. 1 mL of the second solution contains 1 4g of nitrite nitrogen.
14、 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 10 mm optical path length. 4.3 Seven Nessler cylinders, complying with BS612. 4.4 Nine 50 mL stoppered measuring cylinders, complying wi
15、th BS604. 5 Procedure 5.1 Test portion According to the expected nitrite content weigh, to the nearest 0.01 g, a test portion containing up to154g of nitrite nitrogen and, in any case, of mass not more than 25 g. 5.2 Calibration Prepare fresh calibration solutions as follows. Using one of the measur
16、ing 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 measuring cylinder to about 40 mL with water, add2 mL of the sulphanilic acid solution (3.3), mix thoroughly and allow to stand at 22 1 C for
17、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 at22 1 C. NOTEThe 0.0 mL calibration solution is the reagent blank. Using the spectrometer (4.2), measure the absorbance of each calibration solution at appr
18、oximately 525 nm, with water as the reference. Subtract the absorbance value of the reagent blank from that of each calibration solution. Prepare a calibration chart by plotting nitrite nitrogen (in 4g) against absorbance. 5.3 Determination 5.3.1 General. Carry out the determination at the same time
19、 as the procedure described in 5.2, following one of the methods described in 5.3.2 or5.3.3. 5.3.2 Determination by spectrometer. Dissolve the test portion (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 sulphanil
20、ic acid solution (3.3), mix thoroughly and allow to stand at 22 1 C for 20 min to 30 min. Add5 mL of the Cleves acid solution (3.4), dilute to50 mL, mix and allow to stand for a further20min to 30 min at 22 C.BS4267-7:1987 2 BSI 10-1999 Using the spectrometer (4.2), measure the absorbance of this te
21、st solution at the wavelength used in the calibration 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 stand
22、ards (see 5.2) in matched Nessler cylinders. 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: A 1 A 2 where A 1 is the abso
23、rbance of the test solution (5.3.2) A 2 is the absorbance 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:
24、 where m 1 is the mass of nitrite nitrogen found (in 4g); m 0 is 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 of4.57. 6.2 Visual determination The nitrite content, expressed as nitrite nitrogen, N,
25、in mg/kg, is given by the following expression: where 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.BS4267-7:1987; c) the results expressed in accordance with 6.1 or6.2; d) any unusual features
26、noted during the determination; e) any operation not included in this Part of BS4267 or regarded as optional. m 1 m 0 - m 0 is the mass of the test portion (5.1) (in g); m 2 is the mass of nitrite nitrogen in the closest matching calibration standard (5.3.3) (in g). m 2 m 0 -BS4267-7:1987 BSI 10-199
27、9 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. BS 4267-7: 1987 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent n
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