1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 684-2.48: 1998 ICS 67.
2、200.10 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Methods of analysis of fats and fatty oils Part 2. Other methods Section 2.48: Determination of mineral acidityBS 684-2.48:1998 This British Standard, having been prepared under the direction of the Consumer Products and S
3、ervices Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 November 1998 BSI 1998 The following BSI references relate to the work on this standard: Committee reference AW/11 Announced in Standards Update July 1998 ISBN 0 580 28230 9 Amendments
4、issued since publication Amd. No. Date Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee AW/11, Animal and vegetable fats and oils, upon which the following bodies were represented: Association of Public Analy
5、sts Feed Fat Association FOSFA International International Federation of Inspection Agencies Laboratory of the Government Chemist Lard Association Leatherhead Food Research Association Margarine and Shortening Manufacturers Association Ministry of Agriculture, Fisheries and Food Natural Edible Oils
6、Distributors Natural Resources Institute Seed Crushers and Oil Processors Association Soap and Detergent Industry Association Society of Chemical Industry Tropical Growers Association United Kingdom Renderers Association Ltd.BS 684-2.48:1998 BSI 1998 i Contents Page Committees responsible Inside fro
7、nt cover Foreword ii 1 Scope 1 2 Normative references 1 3 Terms and definitions 1 4 Principle 1 5 Reagents 1 6 Apparatus 1 7 Sampling 1 8 Preparation of sample 1 9 Procedure 1 10 Expression of results 1 11 Test report 1 Bibliography 1ii BSI 1998 BS 684-2.48:1998 Foreword This section of BS 684 has b
8、een prepared by Technical Committee AW/11. It is technically identical to clause 5 of BS 684-2.10:1988 which was withdrawn in order to implement, dual-numbered, ISO 660:1996, Animal and vegetable fats and oils Determination of acidity, as BS 684-2.10:1996. Because ISO 660 did not contain a method fo
9、r mineral acidity AW/11 agreed to publish the mineral acidity method (clause 5) from BS 684-2.10:1988 as a new section of BS 684. NOTE It is essential that this section is read in conjuction with the information given in BS 684-0.1 which is published separately. Compliance with a British Standard do
10、es 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, page 1 and a back cover. BSI 1998 1 BS 684-2.48:1998 1 Scope This section of BS 684 describes a method for determination of mineral acidity in all f
11、ats. 2 Normative references The following normative documents contain provisions that, through reference in this text, constitute provisions of this British Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. For undated references, the
12、latest edition of the publication referred to applies. BS 684-2.10:1996, Methods of analysis of fats and fatty oils Part 2: Other methods Section 2.10: Determination of acidity. BS EN ISO 661:1995, Animal and vegetable fats and oils Preparation of test sample. BS EN ISO 3696:1995, Water for analytic
13、al laboratory use Specification and test methods. BS EN ISO 5555:1995, Animal and vegetable fats and oils Sampling. 3 Terms and definitions For the purposes of this British Standard, the following definition applies. 3.1 mineral acidity number of milligrams of potassium hydroxide equivalent to the a
14、cid extracted by water from 100 g of fat 4 Principle A test portion is shaken with light petroleum and water and the separated aqueous layer titrated with sodium or potassium hydroxide solution. 5 Reagents Reagents shall be of recognized analytical grade. Water shall conform to grade 3 of BS EN ISO
15、3696. 5.1 Light petroleum, boiling range 408Ct o6 08 C. 5.2 Sodium hydroxide or potassium hydroxide, standard volumetric solution, c(NaOH) = c(KOH) = 0.01 mol/l. 5.3 Methyl orange indicator, 10 g/l in ethanol solution 95 % (V/V). 6 Apparatus Ordinary laboratory apparatus shall be used. 7 Sampling It
16、 is important that the laboratory receives a sample that is truly representative and has not been damaged or changed during transport or storage. Sampling is not part of the method specified in this standard and a recommended method is given in BS EN ISO 5555. 8 Preparation of sample Prepare the sam
17、ple in accordance with BS EN ISO 661. 9 Procedure 9.1 Test portion Weigh, to the nearest 0.1 g, about 50 g of the test sample (clause 8). 9.2 Determination Transfer the test portion to a 500 ml separating funnel. Add 100 ml of light petroleum (5.1) followed by 50 ml of cold water. Swirl the separati
18、ng funnel but do not shake vigorously. NOTE 1 Stable emulsions may be formed if the contents of the separating funnel are shaken vigorously. Run off the aqueous layer into a conical flask. Wash the light petroleum phase twice with water. Run off the washings (approximately 150 ml) into the flask and
19、 titrate with sodium hydroxide or potassium hydroxide solution (5.2) with methyl orange indicator (5.3). NOTE 2 The end point of titration is reached when addition of a single drop of sodium hydroxide or potassium hydroxide produces a slight but definite colour change persisting for at least 15 s. C
20、arry out two determinations on the test sample (clause 8). 10 Expression of results Calculate the mineral acidity as follows: mineral acidity = 3 100 5.613 V3 c m where V is the volume of sodium hydroxide or potassium hydroxide solution used to titrate the test portion, in milllitres; c is the conce
21、ntration of the standard volumetric sodium hydroxide or potassium hydroxide solution, in moles per litre; m is the mass of the test portion, in grams. The mineral acidity shall be taken as the arithmetic mean of the two determinations. 11 Test report The test report shall show the method used and th
22、e results. Any operating conditions not specified in this standard, or regarded as optional, shall be reported, as well as any incidents that may have influenced the results. The test report shall include all information required for complete identification of the sample. Bibliography BS 684-0.1, Me
23、thods of analysis of fats and fatty oils Part 0: General introduction Section 0.1: General procedures and list of determinations in BS 684.BSI 389 Chiswick High Road London W4 4AL | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
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