1、BRITISH STANDARD BS3762-3.18: 1986 Analysis of formulated detergents Part3: Quantitative test methods Section3.18 Method for determination of chlorine oxidizing agents content NOTEIt is recommended that this Section be read in conjunction with the information in the “General Introduction”, published
2、 separately as BS3762-0. UDC 661.185:543BS3762-3.18:1986 This BritishStandard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authorityofthe Board of BSI andcomes into effect on 31December1985 BSI12-1999 The committees responsible forthis Britis
3、hStandard are showninPart0. The following BSI references relate to the work on this standard: Committee reference CIC/34 Draft for comment84/53114 DC ISBN 0 580 14923 4 Foreword This Section of BS3762 has been prepared under the direction of the Chemicals Standards Committee and supersedes sectionII
4、 of method D9 of BS3762:1964. This standard describes a method of test only and should not be referred to as a specification defining limits of purity. Reference to the standard should indicate that the method of test used is in conformity with BS3762-3.18. A British Standard does not purport to inc
5、lude all 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, page
6、si andii, pages1 and2, 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 issue CommentsBS37
7、62-3.18:1986 BSI 12-1999 i Contents Page Foreword Inside front cover 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Procedure 1 6 Calculation 1 7 Test report 2 Publications referred to Inside back coverii blankBS3762-3.18:1986 BSI 12-1999 1 1 Scope This Section of BS3762 describes a method for
8、 the determination of chlorine oxidizing agents in detergent formulations. The presence of other oxidizing agents may interfere. NOTEThe titles of the publications referred to in this Section are listed on the inside back cover. 2 Principle Potassium iodide is added to the sample. Any chlorine oxidi
9、zing agents react with this to yield iodine. The liberated iodine is determined by visual or potentiometric titration with standard volumetric sodium thiosulphate solution. Results are expressed as available chlorine. 3 Reagents The reagents shall be of a recognized analytical grade. Water complying
10、 with BS3978 shall be used throughout. 3.1 Potassium iodide 3.2 Sulphuric acid solution, c(H 2SO 4 )=5mol/L approximately. 3.3 Sodium thiosulphate solution, c(Na 2 S 2 O 3 )=0.100mol/L. 3.4 Starch indicator,10g/L solution, freshly prepared. 4 Apparatus Ordinary laboratory apparatus, the apparatus de
11、scribed in4.1 and, if potentiometric titration is used, the apparatus detailed in4.2 to4.4 are required. 4.1 One-mark volumetric flask, of250mL capacity, complying with class B of BS1792. 4.2 pH meter (complying with BS3145) or other apparatus suitable for potentiometric titration 4.3 Platinum elect
12、rode 4.4 Calomel reference electrode 5 Procedure 5.1 Test portion Weigh, to the nearest0.05g, approximately10g of sample into a250mL beaker. Add150mL of water and stir to dissolve. Transfer to the250mL one-mark volumetric flask(4.1) and dilute to the mark with water. Transfer an aliquot portion of t
13、his solution to a250mL conical flask as follows. Adjust the total volume in the flask to approximately100mL by addition of water. Weigh approximately2g of the potassium iodide(3.1) and add to the flask. Add10mL of the sulphuric acid solution(3.2). Titrate with the sodium thiosulphate solution(3.3) e
14、ither visually or potentiometrically as described in5.2 or5.3, respectively. 5.2 Visual titration Titrate with the sodium thiosulphate solution until the iodine colour is almost gone. Add1mL of the starch indicator solution(3.4) and complete the titration to the disappearance of the blue colour. Rec
15、ord the titration volume, T. 5.3 Potentiometric titration Introduce the platinum and reference electrodes(4.3 and4.4) connected to the pH meter(4.2) and, while stirring, titrate with the sodium thiosulphate solution. Plot a graph of millivolts or pH scale readings against millilitres of the sodium t
16、hiosulphate solution. Read off the volume, T, in millilitres corresponding to the steepest part of the graph. 6 Calculation The oxidizing agents content, expressed as a percentage by mass of available chlorine, is given by the following expression. Available chlorine content Aliquot volume % (m/m) (
17、mL) 0 to2 100 2 to5 50 5 to10 25 where T is the volume of the sodium thiosulphate solution (inmL); m is the mass of the test portion (ing); A is the volume of the aliquot portion taken in5.1 (inmL).BS3762-3.18:1986 2 BSI 12-1999 7 Test report The test report shall include the following information:
18、a) a reference to this BritishStandard, i.e.BS3762-3.18; b) the results and the method of expression used.BS3762-3.18:1986 BSI 12-1999 Publications referred to BS1792, Specification for one-mark volumetric flasks. BS3145, Specification for laboratory pH meters. BS3978, Water for laboratory use. BS37
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