1、BRITISH STANDARD CONFIRMED APRIL 1993 BS4651-6: 1988 Ammonia solution Part 6: Methods for determination of chloride content NOTEIt is recommended that this Part be read in conjunction with the information on methods for sampling in BS4651-0, published separately. UDC 546.171.1145.2:543.73:546.131BS4
2、651-6:1988 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comesintoeffect on 31August1988 BSI 12-1999 First publishedFebruary1971 First part revision as Part6 The Committees responsible for
3、 this British Standard are shown inPart0. The following BSI references relate to the work on this standard: Committee reference CIC/21 Draft for comment87/51191 DC ISBN 0 580 16537 X Foreword This Part of BS4651 has been prepared under the direction of the Chemicals Standards Committee and supersede
4、s clause6 of BS4651:1971 which is withdrawn. A colorimetric method is given which is technically equivalent to that described in clause6 of BS4651:1971, except that the field of application is limited to products with chloride contents of not more than150mg/kg. For products with higher chloride cont
5、ents, a potentiometric method has been included which refers largely to that described in BS6337-4:1984, possession of which is essential. NOTEThe term “ammonia solution” is used to describe grades of product containing25.0% to35.0% (m/m) ammonia. WARNING. Ammonia solution is a moderately strong alk
6、ali which exerts a local irritant action on the skin. Strong solutions which come into contact with the eyes, even for a short period, can cause serious and permanent damage. Ingestion of ammonia solution will result in the destruction of the mucous lining of the mouth, throat and stomach. Ammonia v
7、apour is readily released from ammonia solution and is combustible in air between the concentrations of16% and27% (V/V) and may explode in confined spaces. When sampling ammonia solution, take the precautions described in BS4651-0. This Part of BS4651 describes a method of test only and should not b
8、e used or quoted as a specification defining limits of purity. Reference to this Part should indicate that the method of test used complies with BS4651-6:1988. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for th
9、eir 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 4, an inside back cover and a back cover. This standard has been updated (s
10、ee 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 issue CommentsBS4651-6:1988 BSI 12-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Method 1. Colorim
11、etric method 1 3 Method 2. Potentiometric method 2 4 Test report 2 Publications referred to Inside back coverii blankBS4651-6:1988 BSI 12-1999 1 1 Scope This Part of BS4651 describes two methods for the determination of the chloride content of ammonia solution for industrial use. The methods are app
12、licable to solutions containing25.0% to35.0% (m/m) of ammonia. Method1 is a colorimetric method applicable to products having a chloride content of not more than150mg/kg. Method2 is a potentiometric method applicable to products having a chloride content of greater than150mg/kg. NOTEThe publications
13、 referred to in this standard are listed on the inside back cover. 2 Method 1. Colorimetric method 2.1 Principle Reaction of the chloride ions present in a test portion with mercury (II) thiocyanate and ammonium iron (III) sulphate, measurement of the absorbance of the resulting solution at a wavele
14、ngth within the range460nm to470nm and determination of the chloride content by means of a calibration graph. 2.2 Reagents 2.2.1 General. During the analysis, use only reagents of recognized analytical grade and water complying with grade3 of BS3978. 2.2.2 Mercury (II) thiocyanate solution. Dissolve
15、 approximately0.1g of mercury (II) thiocyanate and approximately2g of ammonium nitrate in100mL of nitric acid solution, c (HNO 2 )=6mol/L approximately, warming gently to aid dissolution. Filter the solution if necessary. Prepare a fresh solution after one week. 2.2.3 Ammonium iron (III) sulphate so
16、lution. Dissolve10.7g of (NH 4 ) 2SO 4 .Fe 2(SO 4 ) 3 .24H 2 O in100mL of nitric acid solution, c (HNO 3 )=6mol/L approximately. 2.2.4 Standard chloride solution. Dissolve0.1649g of sodium chloride in water in a beaker. Transfer quantitatively to a500mL one-mark volumetric flask and dilute to the ma
17、rk. Using a pipette, transfer5.0mL of this solution to a100mL one-mark volumetric flask and dilute to the mark. One mL of the second solution contains104g of chloride ions. 2.2.5 Sodium carbonate solution, freshly prepared. Dissolve0.1g of anhydrous sodium carbonate in500mL of water. 2.3 Apparatus 2
18、.3.1 General. Ordinary laboratory apparatus and the following. 2.3.2 Spectrometer. Capable of measuring absorbances at wavelengths in the range460nm to470nm and provided with cells of40mm optical path length. 2.3.3 One-mark volumetric flasks, (eight are required),25mL, complying with BS1792. 2.3.4 P
19、latinum dish 2.4 Procedure NOTETake every precaution to avoid chloride contamination while following this procedure, as only low quantities of chloride are to be determined. 2.4.1 Test portion. According to the expected chloride content, transfer an appropriate volume ofthe test sample containing104
20、g to504g of chlorine, from a burette to the small platinum dish(2.3.4), noting the volume to the nearest0.1mL. 2.4.2 Calibration. Into a series of six one-mark volumetric flasks(2.3.3) add respectively 0.0mL,1.0 mL, 2.0 mL, 3.0 mL, 4.0 mL, and5.0mL of the dilute standard chloride solution(2.2.4). Di
21、lute each to about18mL with water, add4.0mL of the ammonium iron(III) sulphate solution(2.2.3), insert the stopper and mix. Remove each stopper, add2.0mL of the mercury(II) thiocyanate(2.2.2) solution, dilute to25mL with water, replace the stopper, mix the contents of the flask and allow it to stand
22、 for20min. NOTEThe0.0mL calibration solution is the first reagent blank, R 1 . Using the spectrometer(2.3.2), measure the absorbance of each solution at a wavelength within the range460nm to470nm with water as the reference. Subtract the absorbance value of the reagent blank, R 1 , from that measure
23、d in each case. Prepare a calibration chart by plotting chloride (in4g) against the corrected absorbance value. NOTEThe graph is not strictly linear over this full calibration range. 2.4.3 Determination. Add to the test portion(2.4.1), a portion of the sodium carbonate solution(2.2.5) in the ratio o
24、f1:5 (for example, add5mL for25mL of test portion) noting the volume. Evaporate to dryness on a boiling water bath, taking care to avoid any loss by spray. Redissolve the residue in5mL of water, then allow to cool. Transfer quantitatively the solution to a one-mark volumetric flask(2.3.3) and dilute
25、 to about18mL with water. Continue by following the procedure described in2.4.2, from“. . ., add4.0mL of the ammonium. . .”, but ignore the reference to the calibration chart.BS4651-6:1988 2 BSI 12-1999 2.4.4 Preparation of the second reagent blank (R 2 ). Prepare the second reagent blank, R 2 , as
26、follows. Toa one-mark volumetric flask(2.3.3) transfer about18mL of water. Add a portion of the sodium carbonate solution equivalent to that used for the determination (see2.4.3). Continue by following the procedure described in2.4.2, from“. . ., add4.0mL of the ammonium. . .”, but ignore the refere
27、nce to the calibration chart. 2.5 Calculation and expression of results Calculate the corrected absorbance from the following expression. A 1 A 2 where Using the corrected value of the absorbance, read the corresponding mass of chloride from the calibration chart. The chloride content, expressed as
28、milligrams of chlorine, CI, per kilogram, is given by the following expression. where 3 Method 2. Potentiometric method 3.1 Principle The principle is described in clause3 of BS6337-4:1984. 3.2 Reagents The reagents described in clause4 of BS6337-4:1984 are required. Use water complyingwith grade3 o
29、f BS3978. 3.3 Apparatus 3.3.1 General. The apparatus described in clause5 of BS6337-4:1984 and the following are required. 3.3.2 Platinum dish, approximately75mL capacity. 3.3.3 One-mark volumetric flask, 100mL, complying with BS1792. 3.4 Procedure 3.4.1 Test portion. Fill the dry one-mark volumetri
30、c flask(3.3.3) to the mark with the test sample. Iftheexpected chloride content of the sample is greater than750mg/kg, take a smaller test portion (see6.1 of BS6337-4:1984). 3.4.2 Preparation of the test solution. Pour some ofthe test portion(3.4.1) into the platinum dish(3.3.2) and place it on a bo
31、iling water bath inawell-ventilated fume cupboard. Carefully evaporate the solution adding more of the test portion until the whole of the100mL has been used. Rinse the one-mark volumetric flask with water and add the washings to the sample in the platinum dish. Continue the evaporation until the ma
32、jority of the ammonia has been released and about10mL ofthe solution is estimated to remain. Transfer quantitatively this residue to a clean dry beaker of suitable capacity (for example,400mL), keeping the volume of the solution to less than50mL. 3.4.3 Determination. Determine the chloride content o
33、f the test solution by following the procedure given in clause6 of BS6337-4:1984 andusing the0.1,mol/L silver nitrate solution. 3.5 Calculation and expression of results Calculate the mass of chloride, expressed as chlorine, Cl, in g, in the test solution from the expression given in clause7 of BS63
34、37-4:1984. The chloride content, expressed as milligrams of chlorine, Cl, per kilogram, is given by the following expression. where 4 Test report The test report shall include the following information: a) a reference to this British Standard, i.e.BS4651-6:1988; b) a reference to the method used, i.
35、e.method1 or method2; c) a complete identification of the sample; d) details of any unusual features noted during the determination; A 1 is the absorbance of the test portion (see2.4.3); A 2 is the absorbance of the second reagent blank, R 2 (2.4.4). m 1 is the mass of chlorine determined(2.4.3) (in
36、4g); V is the volume of the test portion(2.4.1) (inmL); is the density of the test portion at20 C, determined in accordance with BS4651-1 (ing/mL). m 1 V - m 2 is the mass of chloride found (in g); V is the volume of the test portion(3.4.1) (inmL); is the density of the test portion at 20 , determin
37、ed in accordance with BS4651-1 (in g/m L). m 2 10 6 V -BS4651-6:1988 BSI 12-1999 3 e) the results expressed in accordance with2.5 or3.5; f) any operation not included in this British Standard or regarded as optional.4 blankBS4651-6:1988 BSI 12-1999 Publications referred to BS 1792, Specification for
38、 one-mark volumetric flasks. BS 3978, Specification for water for laboratory use. BS 4651, Ammonia solution. BS 4651-0, Methods for sampling. BS 4651-1, Method for determination of density at20 C. BS 6337, General methods of chemical analysis. BS 6337-4, Method for determination of chloride ions by
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