1、BRITISH STANDARD BS 1715-2.9: 1990 Analysis of soaps Part 2: Quantitative test methods Section 2.9 Method for determination of EDTA contentBS1715-2.9:1990 This British Standard, having been prepared under the directionof the Chemicals Standards Policy Committee, waspublished under the authorityof th
2、e Board of BSIandcomes into effect on 31October1990 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference CIC/34 Draft for comment 88/53273 DC ISBN 0 580 18781 7 Committees responsible for this British Standard The preparation of this British Standard was
3、entrusted by the Chemicals Standards Policy Committee (CIC/-) to Technical Committee CIC/34, upon which the following bodies were represented: Chemical Industries Association Chemical Industries Association (GOSIP) Consumer Policy Committee of BSI Department of Trade and Industry (Laboratory of the
4、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 CommentsBS1715-2.9:1990 BSI 09-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Sco
5、pe 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Sampling 1 6 Procedure 1 7 Expression of results 1 8 Precision 2 9 Test report 2 Publication(s) referred to Inside back coverBS1715-2.9:1990 ii BSI 09-1999 Foreword This Section of BS1715 has been prepared under the direction of the Chemicals Standards
6、 Policy Committee. During the preparation of this Section of BS1715, account was taken of ISO4325:1977 “Soaps and detergents Determination of EDTA content (sequestering agent) Titrimetric method”, published by the International Organization for Standardization (ISO). The principal differences betwee
7、n this method and that given in ISO4325 are that they use different indicator systems and that this Section of BS1715 includes a procedure for precipitation and removal of the soap fatty matter. This Section describes a method of test only, and should not be used or quoted as a specification definin
8、g limits of purity. Reference to this Section should indicate that the method of test used is in accordance with BS1715-2.9. 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. Compliance
9、 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 date) and may have had am
10、endments incorporated. This will be indicated in the amendment table on the inside front cover.BS1715-2.9:1990 BSI 09-1999 1 1 Scope This Section of BS1715 describes a titrimetric method for the determination of the content of ethylenediaminetetra-acetic acid (EDTA) and its salts in hard soap, soft
11、soap, toilet soap and soap flakes. It is applicable to soaps with EDTA contents of0.01% to0.1%. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Principle The fatty matter is precipitated and removed from an aqueous solution of the soap. This sol
12、ution is adjusted to pH4.6 and then titrated with standardcopper(II) sulphate solution using 1-(2-pyridylazo)-2-naphthol (PAN) as indicator. 3 Reagents The reagents shall be of a recognized analytical grade. Water complying with grade3 of BS3978 shall be used throughout. 3.1 Hydrochloric acid soluti
13、on, c(HCl)=5mol/L. 3.2 Sodium hydroxide solution, approximately40g/L. 3.3 Copper(II) sulphate standard volumetric solution, c(CuSO 4 )=0.100mol/L. 3.4 PAN indicator, 1g/L solution of1-(2-pyridylazo)-2-naphthol in ethanol. NOTEFor the purposes of 3.4, the ethanol may be replaced by industrial methyla
14、ted spirits complying with BS3591. It should be noted that the use of industrial methylated spirits is governed by the Methylated Spirits Regulations1983 (S.I.1983 No.252). It is not permissible to use duty-free ethanol, received under the provisions of the Alcoholic Liquors Duties Act1972, Section1
15、0, for purposes for which industrial methylated spirits is an accepted alternative. 4 Apparatus Ordinary laboratory apparatus and the following are required. 4.1 pH meter with electrodes and stirrer 4.2 Steam bath, or other heating equipment, capable of being maintained at100 5 C. 4.3 Burette, 10mL
16、capacity, with graduation intervals of0.02mL, and complying with class A of BS846. 5 Sampling The laboratory sample shall have been taken and prepared in accordance with BS1715-1. 6 Procedure 6.1 Test portion Weigh, to the nearest0.01g, into a squat form beaker, a quantity of the laboratory sample s
17、ufficient to give an expected titration of between1mL and5mL e.g.at an expected EDTA content of0.02%(m/m), weigh30g of the sample. 6.2 Removal of the fatty matter Add approximately200mL of hot water to the test portion, place the beaker on the steam bath or other heater maintained at100 5 C(4.2) and
18、 stir to dissolve. While stirring, add a small excess of the hydrochloric acid solution(3.1) to precipitate the soap fatty matter. NOTEFor typical samples, approximately6mL of the hydrochloric acid solution(3.1) is required for each10g of laboratory sample. Continue heating until the fatty matter ha
19、s formed a clear layer at the top, cool and filter into a second beaker through a fast or medium/fast filter paper, previously wetted with water, and wash with hot water. Discard the fatty matter. 6.3 Determination While stirring, introduce the electrodes connected to the pH meter(4.1), which has be
20、en standardized, and carefully add the sodium hydroxide solution(3.2) until the pH is4.6 0.5. Raise the electrodes and rinse them into the beaker. Add0.4mL of the PAN indicator(3.4) and, while stirring, and using the burette(4.3), titrate with the copper(II) sulphate solution(3.3) until the colour c
21、hanges from yellow to wine red. NOTEThe wine red colour should persist for at least1min. 6.4 Blank determination Carry out a blank determination by titrating200mL of water adjusted to pH4.6 0.5 until the colour of the blank determination and that of the sample determination are the same. 7 Expressio
22、n of results Subtract the volume of the copper(II) sulphate solution used for the blank determination from the volume used for the sample determination, to produce the corrected titration volume V. The EDTA content, expressed as a percentage by mass, is given by the following expression: where V is
23、the corrected titration volume of the copper(II) sulphate solution used (in mL); m is the mass of the test portion (in g); V 0.01 1000 -292 100 m - BS1715-2.9:1990 2 BSI 09-1999 292 is the relative molecular mass of EDTA (freeacid). 8 Precision No precision data are available. 9 Test report The test
24、 report shall include the following information: a) a reference to this British Standard, i.e.BS1715-2.9:1990; b) the results expressed in accordance with clause7; c) a complete identification of the sample.BS1715-2.9:1990 BSI 09-1999 Publication(s) referred to BS 846, Specification for burettes. BS
25、 1715, Analysis of soaps. BS 1715-1, General introduction, sampling, and test for presence of synthetic anionic-active surface active agents. BS 3591, Specification for industrial methylated spirits. BS 3978, Specification for water for laboratory use. BS 1715-2.9: 1990 BSI 389 Chiswick High Road Lo
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