1、BRITISH STANDARD BS 1715-2.4: 1989 Analysis of soaps Part 2: Quantitative test methods Section 2.4 Method for determination of free fatty acids content UDC 661.18.187 492:665.12:620.113BS1715-2.4:1989 This British Standard, having been prepared under the directionof the Chemicals Standards Policy Co
2、mmittee, waspublished under the authorityof the Board of BSI andcomes into effect on 31January1990 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference CIC/34 Draft for comment88/55440 DC ISBN 0 580 17861 7 Committees responsible for this British Standard
3、 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 BSI Department of the Environment Department of Tr
4、ade 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 CommentsBS1715-2.4:1989 BSI 08-1999 i Contents Page Committees res
5、ponsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Sampling 1 7 Procedure 1 8 Expression of results 2 9 Precision 2 10 Test report 2 Table 1 Expression of free fatty acids 1 Publications referred to Inside back coverBS1715-2.4:1989 ii BSI 08-
6、1999 Foreword This Section of BS1715 has been prepared under the direction of the Chemicals Standards Policy Committee. It supersedes the method “Free fatty acids” given in BS1715:1963, which will be deleted by amendment. This Section describes a method of test only, and should not be used or quoted
7、 as a specification defining limits of purity. Reference to this Section should indicate that the method of test used is in accordance with BS1715-2.4. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their corr
8、ect 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, pages1 and 2, an inside back cover and a back cover. This standard has been updated (see copyr
9、ight date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS1715-2.4:1989 BSI 08-1999 1 1 Scope This Section of BS1715 describes a method for the determination of the free fatty acids content of alkali metal soaps. It may be expresse
10、d either as free fatty acid content or as acid value. The method is not applicable in the presence of ethanolamine soaps. NOTEThe titles of the publications referred to in this Section are listed on the inside back cover. 2 Definitions For the purposes of this Section of BS1715 the following definit
11、ions apply. 2.1 free fatty acids content a conventional expression of the percentage by mass of free fatty acids NOTEAccording to the type of soap, the free fatty acids content can be expressed as given inTable 1. Table 1 Expression of free fatty acids 2.2 acid value the number of milligrams of pota
12、ssium hydroxide required to neutralize the free fatty acids in1g of soap 3 Principle A test portion is dissolved in hot ethanol solution and titrated with an aqueous solution of sodium hydroxide. 4 Reagents The reagents shall be of a recognized analytical grade. Water complying with grade3 of BS3978
13、 shall be used throughout. 4.1 Ethanol 95% (V/V) solution in water NOTEFor the purposes of4.1 and4.3 the ethanol may be replaced by industrial methylated spirits complying with BS3591 and of appropriate strength. It should be noted that the use of industrial methylated spirits is governed by the Met
14、hylated Spirits Regulations, 1983 (S.I.1983 No.252). It is not permissible to use duty-free ethanol, received under the provisions of the Alcoholic Liquors Duties Act1972, Section10, for purposes for which industrial methylated spirits is an acceptable alternative. 4.2 Sodium hydroxide standard volu
15、metric solution, c(NaOH) = 0.100mol/L. 4.3 Phenolphthalein indicator solution, 5g/L in50% (V/V) ethanol solution. 5 Apparatus 5.1 Ordinary laboratory apparatus 6 Sampling The laboratory sample shall have been taken in accordance with BS1715-1. 7 Procedure 7.1 Test portion Weigh, to the nearest0.01g,
16、 approximately5g of the laboratory sample into a250mL conical flask. 7.2 Determination Heat to boiling point100mL of the ethanol (4.1) in a second250mL conical flask. While the temperature of the ethanol solution is still over70 C, neutralize with the sodium hydroxide solution (4.2) using0.5mL of th
17、e phenolphthalein indicator solution (4.3). Add the neutralized ethanol to the test portion in the first flask and swirl to dissolve the test portion, heating if necessary. Maintain the temperature at approximately70 C, and titrate with the sodium hydroxide solution (4.2). NOTEThe end point of the t
18、itration is reached when the addition of a single drop produces a slight but definite colour change to pink persisting for at least15s. 8 Expression of results 8.1 Free fatty acid content The free fatty acid content, expressed as a percentage by mass, is given by the following expression where V is
19、the volume of the sodium hydroxide solution used to titrate the test portion (in mL); M is the relative molecular mass of the acid chosen for expression of the result (seeTable 1); m is the mass of the test portion (in g). Type of acid Relative molecular mass Lauric acid Palmitic acid Oleic acid 200
20、 256 282 V 0.1 M 1 000 - 100 m - VM 0.01 m - =BS1715-2.4:1989 2 BSI 08-1999 8.2 Acid value The acid value is given by the following expression where V and m are as given in8.1. 9 Precision No precision data are available. 10 Test report The test report shall include the following information: a) a r
21、eference to this British Standard, i.e.BS1715-2.4:1989; b) the results expressed in accordance with8.1, including the relative molecular mass used in the calculation, or8.2; c) a complete identification of the sample. V 0.1 56.1 m -BS1715-2.4:1989 BSI 08-1999 Publications referred to BS 1715, Analys
22、is 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 1715-2.4: 1989 BSI 389 Chiswick High Road London W4 4AL B
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