1、BRITISH STANDARD BS 4267-8: 1987 Ammonium nitrate Part 8: Methods for determination of chloride 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
2、oxidizing agent. If necessary, break the test sample up by crushing rather than grinding. UDC 661.525:546.39175:543BS4267-8:1987 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comes intoeff
3、ect on 30 September 1987 BSI 10-1999 The Committees responsible for this British Standard are shown inPart 0 The following BSI references relate to the work on this standard: Committee reference CIC/21 Draft (ref. 86/53125) announced inBSI News, September 1986 ISBN 0 580 16121 8 Foreword This Part o
4、f BS 4267 has been prepared under the direction of the Chemicals Standards Committee. It supersedes clause 10 of BS 4267:1968, which has been deleted by amendment. A colorimetric method is given which is technically equivalent to the method that was described in clause 10 of BS 4267:1968, except tha
5、t the field of application has been limited to chloride contents of not more than 150 mg/kg. A potentiometric method has been included which refers to BS 6337-4:1984 (identical with ISO 6227:1982). This standard describes methods of test only, and should not be used or quoted as a specification defi
6、ning limits of purity. Reference to this Partshould indicate that the methods of test used are in accordance with BS4267-8:1987. 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. Compli
7、ance 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 hav
8、e 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 CommentsBS4267-8:1987 BSI 10-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Colorimetric method 1 3 Potentiometric method 2
9、 4 Test report 2 Publications referred to Inside back coverii blankBS4267-8:1987 BSI 10-1999 1 1 Scope This Part of BS 4267 describes two methods for determination of the chloride content of ammonium nitrate for industrial use. Clause 2 describes a colorimetric method, which is applicable to product
10、s having chloride contents of not more than 150 mg/kg. Clause 3 describes a potentiometric method, which is applicable to products having chloride contents greater than 150 mg/kg. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Colorimetric meth
11、od 2.1 Principle The chloride ions present in a test portion are reacted with mercury (II) thiocyanate and ammonium iron (III) sulphate. The absorbance of the resulting solution is measured at a wavelength within the range 460 nm to 470 nm and the chloride content is determined by means of a calibra
12、tion graph. 2.2 Reagents 2.2.1 General. During the analysis, use only reagents of recognized analytical grade and water complying with BS 3978. 2.2.2 Mercury (II) thiocyanate solution. Dissolve0.1g of mercury (II) thiocyanate and 2 g of ammonium nitrate in 100 mL of nitric acid solution, c(HNO 3 ) =
13、 63 g/L, warming gently to aid dissolution. Filter the solution if necessary. 2.2.3 Ammonium iron (III) sulphate solution. Dissolve 10.7 g of (NH 4 ) 2 SO 4 ,Fe 2 (SO 4 ) 3 .24H 2 O in100mL of nitric acid solution, c(HNO 3 ) = 378 g/L. 2.2.4 Sodium chloride, standard solution. Dissolve0.1649 g of so
14、dium chloride in water in the volumetric flask (2.3.4) and dilute to the mark. Further dilute 5 mL of this solution to 100 mL immediately before use. In the second solution 1 mL contains 10 4g of chloride ions. 2.2.5 Nitric acid solution, c(HNO 3 ) = 378 g/L approximately. 2.3 Apparatus 2.3.1 Ordina
15、ry laboratory apparatus 2.3.2 Spectrometer, capable of measuring absorbances at wavelengths in the range 460 nm to470 nm and provided with cells of 40 mm optical path length. 2.3.3 Nine 25 mL stoppered measuring cylinders, complying with BS 604. 2.3.4 One-mark volumetric flask, 500 mL, complying wit
16、h BS 1792. 2.4 Procedure 2.4.1 Test portion. Weigh, to the nearest 1 mg, approximately 0.3 g of the test sample. 2.4.2 Calibration. Using one measuring cylinder(2.3.3) for each calibration solution, add successively 0.0, 1.0, 2.0, 3.0, 4.0 and 5.0 mL of the dilute standard chloride solution (2.2.4).
17、 Make up each measuring cylinder to about 18 mL with water, add 4 mL of the ammonium iron (III) sulphate solution (2.2.3), insert the stopper and mix the solutions. Remove each stopper, add 2 mL of the mercury (II) thiocyanate solution (2.2.2), dilute to25 mL with water, replace the stopper, mix the
18、 contents of the measuring cylinder and allow it to stand for 10 min to 20 min. NOTEThe 0.0 mL calibration solution is the reagent blank. Using the spectrometer (2.3.2), measure the absorbance of each calibration solution at a wavelength within the range 460 nm to 470 nm with water as the reference.
19、 Subtract the absorbance value of the reagent blank from that of each calibration solution. Prepare a calibration chart by plotting chloride (in 4g) against the corrected absorbance value. 2.4.3 Preparation of the sample blank. Add 0.3 g of the test sample to one of the measuring cylinders(2.3.3), d
20、issolve in about 18 mL of water, add 4.5 mL of the nitric acid solution (2.2.5), insert the stopper and mix the solutions. Remove the stopper, dilute to 25 mL with water, replace the stopper, mix the contents of the measuring cylinder and allow it to stand for 10 min to 20 min. Using the spectromete
21、r (2.3.2), measure the absorbance of the solution at the wavelength used in the calibration and with water as the reference. NOTEThis blank compensates for the inherent colour or turbidity occasionally found in samples of ammonium nitrate solution. 2.4.4 Determination. Transfer the test portion(2.4.
22、1) to one of the measuring cylinders(2.3.3), dissolve in about 18 mL of water and allow the solution to reach room temperature. Add 4 mL of the ammonium iron (III) sulphate solution (2.2.3), insert the stopper and mix the solutions. Remove the stopper, add 2 mL of the mercury (II) thiocyanate soluti
23、on (2.2.2), dilute to25 mL with water, replace the stopper, mix the contents of the measuring cylinder and allow it to stand for 10 min to 20 min. Using the spectrometer (2.3.2), measure the absorbance of the test solution at the wavelength used in the calibration and with water as the reference.BS4
24、267-8:1987 2 BSI 10-1999 2.5 Calculation and expression of results Calculate the corrected absorbance from the following expression: A 1 (A 2 + A 3 ) where Using the corrected value of the absorbance, read the corresponding mass of chloride from the calibration graph. The chloride content, expressed
25、 as chlorine, Cl, inmg/kg, is given by the following expression: where 3 Potentiometric method 3.1 Principle The principle is described in clause 3 of BS6337-4:1984. 3.2 Reagents The reagents described in clause 4 of BS6337-4:1984 are required. 3.3 Apparatus 3.3.1 General. The apparatus described in
26、 clause 5 of BS 6337-4:1984 and the item described in 3.3.2 are required. 3.3.2 100 mL one-mark volumetric flask, complying with class B of BS 1792. 3.4 Procedure 3.4.1 Test portion and preparation of the test solution. Weigh, to the nearest 0.01 g, approximately 20 g of the test sample and transfer
27、 this test portion to the one-mark volumetric flask(3.3.2). Dissolve the test portion in water, dilute to the mark and mix. 3.4.2 Determination. Determine the chloride content of the test solution by following the procedure described in clause 6 of BS 6337-4:1984, using an appropriate amount of the
28、test solution depending on the expected chloride ion content. 3.5 Calculation and expression of results Calculate the mass of chloride, expressed as grams of chlorine (Cl), in the test solution from the formula given in clause 7 of BS 6337-4:1984. The chloride content, expressed as a percentage by m
29、ass of chlorine (Cl), is given by the following expression: where 4 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. BS4267-8:1987; c) the results expressed in accordance with 2.5 or3.5; d) any unus
30、ual features noted during the determination; e) any operation not included in this Part of BS4267 or regarded as optional. A 1 is the absorbance of the test solution; A 2 is the absorbance of the reagent blank (2.4.2); A 3 is the absorbance of the sample blank (2.4.3). m 1 is the mass of chloride fo
31、und (in 4g); m 0 is the mass of the test portion (2.4.1) (in g). m 1 m 0 - m 1 is the mass of chloride in the test solution (in g); m 0 is the mass of the test portion (in g). m 1 m 0 -100 BS4267-8:1987 BSI 10-1999 Publications referred to BS 604 , Specification for graduated glass measuring cylinde
32、rs. BS 1792, Specification for one-mark volumetric flasks. BS 3978, Specification for water for laboratory use. BS 6337, General methods of chemical analysis. BS 6337-4, Method of determination of chloride ions by potentiometry . BS 4267-8: 1987 BSI 389 Chiswick High Road London W4 4AL BSIBritishSta
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