1、BRITISH STANDARD BS 4651-7: 1988 Ammonia solution Part 7: Method for determination of carbon dioxide content NOTEIt is recommended that this Part be read in conjunction with the information on methods for sampling in BS4651-0, published separately. UDC 546.171.1 145.2:543.73:546.264 31BS4651-7:1988
2、This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 31August1988 BSI 11-1999 First published February1971 First part revision as Part 7 The committees responsible for this Br
3、itish Standard are shown inPart 0. The following BSI references relate to the work on this standard: Committee reference CIC/21 Draft for comment 87/51192 DC ISBN 0 580 16539 6 Foreword This Part of BS4651 has been prepared under the direction of the Chemicals Standards Committee and supersedes clau
4、se 7 of BS4651:1971 which is withdrawn. This method is technically equivalent to that described in clause 7 of BS4651:1971. NOTEThe term “ammonia solution” is used to describe grades of product containing25.0% to35.0% (m/m) of ammonia. WARNING. Ammonia solution is a moderately strong alkali which ex
5、erts 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 vapour is rea
6、dily 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 BS 4651-0. This Part of BS4651 describes a method of test only and should not be used or q
7、uoted as a specification defining limits of purity. Reference to this Part should indicate that the method of test used complies with BS4651-7:1988. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct
8、 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, pagesi andii, pages1 and2, an inside back cover and a back cover. This standard has been updated (see copyright d
9、ate) 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 CommentsBS4651-7:1988 BSI 11-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Principle 1 3 Reagents 1 4 Appa
10、ratus 1 5 Procedure 1 6 Expression of results 2 7 Test report 2 Publications referred to Inside back coverii blankBS4651-7:1988 BSI 11-1999 1 1 Scope This Part of BS4651 describes a titrimetric method for the determination of the carbon dioxide content of ammonia solution for industrial use. The met
11、hod is applicable to solutions containing25.0% to35.0% (m/m) of ammonia and with a carbon dioxide content of not lower than10mg/kg. NOTEThe publications referred to in this standard are listed on the inside back cover. 2 Principle The carbon dioxide present is precipitated as barium carbonate and th
12、e filtered precipitate is washed free from alkali and dissolved in a known excess of standard acid, which is back-titrated with standard sodium hydroxide solution. 3 Reagents 3.1 General. During the analysis, use only reagents of recognized analytical reagent grade and water complying with grade3 of
13、 BS3978, freshly boiled to be free from carbon dioxide. 3.2 Barium chloride solution, 100 g/L. 3.3 Sodium hydroxide solution, c(NaOH) =40 g/L, approximately. 3.4 Sodium hydroxide, standard volumetric solution, c(NaOH) =0.100 mol/L. 3.5 Hydrochloric acid, standard volumetric solution, c(HCl) =0.100 m
14、ol/L. 3.6 Screened methyl orange indicator solution, 1 g/L. Dissolve0.25g of methyl orange and0.15g of xylene cyanol FF in50mL of95% (V/V) ethanol and dilute to250mL with water. 3.7 Phenolphthalein indicator solution, 10g/L in95% (V/V) ethanol. NOTEFor the purposes of3.6 and3.7, ethanol may be repla
15、ced by industrial methylated spirits95% (V/V) complying with BS3591. It should be noted that the use of industrial methylated spirits is governed by The Methylated Spirits Regulations,1983 (S.I.1983 No.252). It is not permissible to use duty-free ethanol, received under the provisions of the Alcohol
16、ic Liquors Duties Act1972, Section10, for purposes for which industrial methylated spirits is an acceptable alternative. 4 Apparatus 4.1 General. Ordinary laboratory apparatus and the following. 4.2 One-mark volumetric flask, 100 mL, complying with BS1792. 4.3 Carbon-dioxide absorber guard tube 5 Pr
17、ocedure 5.1 Test portion Fill the one-mark volumetric flask (4.2) to the mark with the test sample. 5.2 Determination Transfer the test portion (5.1) to a clean, dry,250mL conical flask. Add10mL of the barium chloride solution (3.2) and5mL of the sodium hydroxide solution (3.3). Boil gently until al
18、l trace of ammonia odour is absent and close the flask with a stopper fitted with the guard tube (4.3). Allow the flask to cool. Remove the guard tube (4.3) and add a few drops of the phenolphthalein indicator solution (3.7). Partially neutralize the excess sodium hydroxide by carefully adding45.0mL
19、 of the hydrochloric acid solution(3.5). Filter the contents of the flask through a small, fine, acid-washed filter paper. Rinse the flask well with carbon dioxide-free water, passing the washings through the filter paper. Wash the filter thoroughly until10mL to20mL of the filtrate are shown to be f
20、ree from sodium hydroxide when tested with the phenolphthalein indicator solution (3.7). Place the filter paper and contents in the original flask together with50mL of water previously neutralized to the screened methyl orange indicator solution (3.6). Add, from a burette, a portion of the hydrochlo
21、ric acid solution (3.5), sufficient just todissolve the barium carbonate and to give a slightexcess. Note the volume added to the nearest0.1mL. Warm gently for10min, ensuring that any precipitate adhering to the sides of the flask is dissolved. Cool, add0.2mL of the screenedmethyl orange indicator s
22、olution (3.6) andback-titrate the excess acid with the sodium hydroxide standard solution (3.4). 5.3 Blank test Carry out a blank test by following the procedure described in5.2, but with100mL of the carbon dioxide-free water replacing the sample.BS4651-7:1988 2 BSI 11-1999 6 Expression of results T
23、he carbonate content, expressed as milligrams of carbon dioxide (CO 2 ) per kilogram, is given by the following expression. where 7 Test report The test report shall include the following information: a) a reference to this British Standard, i.e.BS4651-7:1988; b) a complete identification of the sam
24、ple; c) details of any unusual features noted during the determination; d) the results expressed in accordance with clause6; e) any operation not included in this British Standard or regarded as optional. V 1 is the volume of hydrochloric acid solution(3.5) added in the final titration (see5.2) (in
25、mL); V 2 is the volume, of sodium hydroxide solution(3.4) used in the back titration (see5.2) (in mL); V 3 is the volume of hydrochloric acid solution(3.5) added to the reagent blank in the final titration (see5.3) (in mL); V 4 is the volume of sodium hydroxide solution(3.4) added to the reagent bla
26、nk in the back titration (see5.3) (in mL); 500 is the volume of the test portion (5.1) (inmL); is the density of the test sample at20 C, determined in accordance with the method described in BS4651-1 (in g/mL); 0.0022 is the mass of carbon dioxide equivalent to1mL of the hydrochloric acid solution(3
27、.5) (ing).BS4651-7:1988 BSI 11-1999 Publications referred to BS 1792, Specification for one-mark volumetric flasks. BS 3591, Specification for industrial methylated spirits. BS 3978, Specification for water for laboratory use. BS 4651, Ammonia solution. BS 4651-0, Methods of sampling. BS 4651-1, Met
28、hod for determination of density at20 C. BS 4651-7: 1988 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incor
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