1、BRITISH STANDARD BS1715-2.7: 1989 ISO4323:1977 Analysis of soaps Part2: Quantitative test methods Section2.7 Method for determination ofchloride content ISO title: SoapsDetermination of chloride content Potentiometric method UDC661.18:543BS1715-2.7:1989 This British Standard, having been prepared un
2、der the directionof the Chemicals Standards Policy Committee, waspublished under the authorityof the Board of BSI andcomes intoeffect on 31 July1989 BSI09-1999 The following BSI references relate to the work on this standard: Committee reference CIC/34 Draft for comment88/53275 DC ISBN0 580 17323 2
3、Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Chemicals Standards Policy Committee (CIC/-) to Technical Committee CIC/34, upon which the following bodies were represented: Chemical Industries Association Consumer Policy Committee of BS
4、I Department of the Environment Department of Trade and Industry (Laboratory of the Government Chemist) Ministry of Defence Royal Society of Chemistry Soap and Detergent Industry Association Society of Dyers and Colourists Amendments issued since publication Amd. No. Date of issue CommentsBS1715-2.7
5、:1989 BSI 09-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of application 1 2 Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Sampling 1 7 Procedure 1 8 Expression of results 3 9 Test report 3 Annex Example 4 Publications referred to Ins
6、ide back coverBS1715-2.7:1989 ii BSI 09-1999 National foreword This Section of BS1715 has been prepared under the direction of the Chemicals Standards Policy Committee. It is identical with ISO4323:1977 “Soaps Determination of chloride contentPotentiometric method” published by the International Org
7、anization for Standardization (ISO). This method supersedes the method “Determination of chlorides” given in BS1715:1963, which is deleted by amendment. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without dev
8、iation. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker.
9、 The symbol “1” has been used to denote litre (and in its submultiples). In British Standards it is current practice to use the symbol “L”. Wherever the words “International Standard” appear, referring to this standard, they should be read as “Section of BS1715”. Cross references. The International
10、Standard for sampling of soaps (seeclause2 and clause6) is not yet published. Relevant information is included in BS1715 “Analysis of soaps”, Part1:1989 “General introduction, sampling, and test for presence of synthetic anionic-active surface active agents”. ISO/R385 (see5.5) has been revised as IS
11、O385-1:1984, ISO385-2:1984 and ISO385-3:1984; a related British Standard is BS846:1985 “Specification for burettes”. Additional information. With reference to clause4, water complying with grade3 of BS3978 “Specification for water for laboratory use” is suitable. With reference to4.2, the nitric aci
12、d solution, expressed as an amount-of-substance concentration, is c(HNO 3 )=6mol/L. With reference to4.3 and4.4, the silver nitrate solutions, expressed as amount-of-substance concentrations, are c(AgNO 3 )=0.1mol/L and c(AgNO 3 )=0.01mol/L respectively. With reference to4.5 and4.6, the potassium ch
13、loride standard reference solutions, expressed as amount-of-substance concentrations, arec(KCl)=0.1mol/L and c(KCl)=0.01mol/L respectively. In7.3.3 and clause8, “normality” should be read as “amount-of-substance concentration (mol/L)”. This Section describes a method of test only, and should not be
14、used or quoted as a specification defining limits of purity. Reference to this Section should indicate that the method of test used is in accordance with BS1715-2.7. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible
15、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, pagesi andii, pages1 to4, an inside back cover and a back cover. This standard has been updated
16、(see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS1715-2.7:1989 BSI 09-1999 1 1 Scope and field of application This International Standard specifies a potentiometric method for the determination of the chloride co
17、ntent of commercial soaps, containing or not containing other surface active agents, and also of compounded products. 2 Reference ISO., SoapsSampling 1) . 3 Principle Potentiometric titration of the chloride (Cl ) ions with standard volumetric silver nitrate solution in a nitric acid medium, using a
18、 silver-silver chloride measurement electrode and a calomel reference electrode. 4 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Potassium nitrate, solution saturated at20 C. 4.2 Nitric acid, approximately6N
19、 solution. 4.3 Silver nitrate, approximately0,1N standard volumetric solution. Dissolve8,5g of silver nitrate in water in a500ml one-mark volumetric flask, dilute to the mark and mix. Store this solution in a dark amber-coloured flask. 4.4 Silver nitrate, approximately0,01N solution. Prepare this so
20、lution immediately before use by appropriate dilution of the standard volumetric silver nitrate solution(4.3). 4.5 Potassium chloride, 0,1N standard reference solution. Weigh, to the nearest0,001g,3,728g of potassium chloride, previously dried for2h at105 C and cooled in a desiccator. Dissolve in a
21、small quantity of water and transfer quantitatively to a500ml one-mark volumetric flask. Dilute to the mark and mix. 4.6 Potassium chloride, 0,01N standard reference solution. Prepare this solution immediately before use by appropriate dilution of the standard reference potassium chloride solution(4
22、.5). 4.7 Methyl orange,1g/l solution. 5 Apparatus Ordinary laboratory apparatus, and 5.1 Potentiometer, sensitivity2mV, covering the range500 to+500mV. 5.2 Electrodes 5.2.1 Calomel electrode KCl saturated 5.2.2 Silver-silver chloride electrode 5.2.3 Bridge, containing the saturated potassium nitrate
23、 solution(4.1), connected to the calomel electrode(5.2.1). 5.3 Combined electrode, as an alternative to the calomel electrode(5.2.1) and the silver electrode(5.2.2). 5.4 Electromagnetic stirrer 5.5 Burette, capacity50ml, complying with the requirements of ISO/R385, Class A. 6 Sampling The laboratory
24、 sample of soap shall be prepared and stored according to the procedure specified in ISO. 7 Procedure 7.1 Measurement temperature In order to reduce the effects of thermal and electric hysteresis, take care that the temperatures of the electrodes, the water used for washings, the standard solutions
25、and the test solution are as close to each other as possible. The temperatures of the standard solutions and the test solution shall not differ by more than1 C. The measurement temperature should be20 C whenever possible. 7.2 Test portion and preparation of test solution Select the reagent solutions
26、 and test portion according to the expected chloride content, as indicated in the following table: 1) In preparation. Expected chloride content expressed as NaCl % (m/m) Silver nitrate solution Standard reference potassium chloride solution Mass of testportion Below0,1 Above0,1 0,01N(4.4) 0,1N(4.3)
27、0,01N(4.6) 0,1N(4.5) 1 to10g 1 to3gBS1715-2.7:1989 2 BSI 09-1999 Weigh, to the nearest0,001g, the appropriate test portion and dissolve in50 to100ml of hot water. Add2 drops of the methyl orange solution(4.7), acidify with the nitric acid solution(4.2) and add several drops in excess. Filter through
28、 a wet filter paper and wash the fatty acids with small portions of hot water. Cool the filtrate, i.e.the test solution for titration, to20 C. 7.3 Calibration of the silver nitrate solution 7.3.1 Preparation of the apparatus Assemble the apparatus and switch it on. Allow it to operate, according to
29、the manufacturers instructions, for a sufficient time to obtain a good electric stabilization before beginning the measurements. Take care that the interior liquid of the KCl-saturated calomel electrode(5.2.1) is in equilibrium with the atmospheric pressure, in order that its outflow across the brid
30、ge(5.2.3) is not obstructed. Note the temperature of the standard reference solutions, make the corresponding adjustments in the circuit for correction of temperatures, and verify the zero of the apparatus. Do not alter the settings during the measurements. 7.3.2 Titration Take5,00ml and10,00ml resp
31、ectively of the appropriate standard reference potassium chloride solution(4.5 or4.6) and place in two clean, dry vessels of convenient capacity (for example150ml). Carry out the following titration on the contents of each vessel. After acidification by the nitric acid solution(4.2), add sufficient
32、water to bring the total volume to about100ml. Stir the resultant solution and immerse the combined electrode(5.3) or the silver-silver chloride electrode(5.2.2) and the free end of the bridge(5.2.3) in the solution, connect the electrode to the potentiometer(5.1) and, after having verified the zero
33、 of the apparatus, note the value of the starting potential. Add, from the burette(5.5), in1ml portions, the silver nitrate solution(4.3 or4.4) having the same normality as that of the standard reference potassium chloride solution(4.5 or4.6) used. After each addition, await the stabilization of the
34、 potential. Record the volumes added and the corresponding values of the potential in the first two columns of a table. When approaching the end-point, continue the addition of the silver nitrate solution in portions of0,1ml for the0,01N solution or0,05ml for the0,1N solution. In a third column of t
35、he table, record the successive increments% 1 E of the potential E. In a fourth column, record the differences% 2 E, positive or negative, between the potential increments% 1 E. The end of the titration corresponds to the addition of the0,1ml or0,05ml portion of the silver nitrate solution which giv
36、es the maximum value of% 1 E. In order to calculate the exact volume V EQof the silver nitrate solution corresponding to the end of the reaction, use the formula: 7.3.3 Calculation of normality of solution The normality T of the silver nitrate solution is given by the formula where V 0 is the volume
37、, in millilitres, of the silver nitrate solution(4.3 or4.4), immediately lower than the volume which gives the maximum increment of% 1 E; V 1 is the volume, in millilitres, of the final portion of silver nitrate solution(4.3 or4.4) added(0,05 or0,1ml respectively); b is the last value of% 2 E which
38、is positive; B is the sum of the absolute values of the final positive value of% 2 E and the first negative value of% 2 E (seeexample inAnnex). where T 0 is the normality of the standard reference potassium chloride solution(4.5 or4.6); V 2 is the value, in millilitres, of V EQ , corresponding to th
39、e titration of10ml of the standard reference potassium chloride solution(4.5 or4.6); V 3 is the value, in millilitres, of V EQ , corresponding to the titration of5ml of the standard reference potassium chloride solution(4.5 or4.6); 5is the difference, in millilitres, between the two volumes of stand
40、ard reference potassium chloride solution(4.5 or4.6) used. V EQ V 0 V 1 b B - + = TT 0 5 V 2 V 3 - =BS1715-2.7:1989 BSI 09-1999 3 7.4 Blank test Carry out a blank test without the test portion. The value of the blank test on the reagents, V 4 , is given, in millilitres, by the formula V 4 =2V 3 V 2
41、where V 2and V 3are as defined in7.3.3. 7.5 Determination Titrate the test solution(7.2) with the silver nitrate solution(4.3 or4.4) corresponding to the expected chloride content and note the end-point of the reaction in accordance with the instructions given in7.3. 8 Expression of results The chlo
42、ride content is given, as a percentage by mass of sodium chloride (NaCl), by the formula 9 Test report The test report shall include the following particulars: a) all information necessary for the complete identification of the sample; b) the reference of method used (reference to this International
43、 Standard); c) the results and the method of expression used; d) the test conditions; e) any operational details not specified in this International Standard or the International Standard to which reference is made, or regarded as optional, as well as all incidents likely to have affected the result
44、s. where T is the normality of the silver nitrate solution, calculated in accordance with7.3.3; V 4 is the volume, in millilitres, corresponding to the blank test(7.4); V 5 is the value, in millilitres, of V EQ , corresponding to the determination(7.5); m is the mass, in grams, of the test portion (
45、see7.2). V 5 V 4 ()T 0,058 5 100 m - 5,85 TV 5 V 4 () m - =BS1715-2.7:1989 4 BSI 09-1999 Annex Example Volume of silver nitrate solution(4.4) Potential % 1 E % 2 E V E ml mV 0,80 0,90 1,00 1,10 1,20 176 211 283 306 319 35 72 23 13 +37 49 10 V EQ 0,90,1 37 3749 + -0,943 = + =BS1715-2.7:1989 BSI 09-19
46、99 Publications referred to Seenational foreword.BS1715-2.7: 1989 ISO4323:1977 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 internatio
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