《BS-684-1.6-1988 ISO-935-1988.pdf》由会员分享，可在线阅读，更多相关《BS-684-1.6-1988 ISO-935-1988.pdf（10页珍藏版）》请在三一文库上搜索。
1、BRITISH STANDARD CONFIRMED APRIL 1993 BS 684-1.6: 1988 ISO 935:1988 Methods of analysis of Fats and fatty oils Part 1: Physical methods Section 1.6 Determination of titre ISO title: Animal and vegetable fats and oils Determination of titre IMPORTANT NOTE. It is essential that BS 684-0, which is publ
2、ished separately, be read in conjunction with this Section. UDC 665.1.014:665.2/.3:665.7:620.171.32:620.1:(083.71) Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.6:1988 This British Standard, having been prepared under the directio
3、n of the Food and Agriculture Standards Committee, was published under the authority of the Board of BSI and comes into effect on 30 November 1988 BSI 10-1999 First published October 1976 First revision November 1988 The following BSI references relate to the work on this standard: Committee referen
4、ce FAC/18 Draft for comment 86/53151 DC ISBN 0 580 16972 3 National foreword This Section of BS 684 has been prepared under the direction of the Food and Agriculture Standards Committee and supersedes BS 684-1.6:1976 which is withdrawn. It is identical with ISO 935:1988 “Animal and vegetable fats an
5、d oils Determination of titre” published by the International Organization for Standardization (ISO) and in the preparation of which the United Kingdom played a full part. The principal differences from the 1976 edition are that saponification is carried out in glycerol and not ethanol solution and
6、stirring is continuous during the determination of titre. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British S
7、tandards; 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. The symbol “l” has been used to denote litre (and in its submultiples). In British Standards i
8、t is current practice to use the symbol “L”. In British Standards it is current practice to use the spelling “sulphur”, etc., instead of “sulfur”, etc. Wherever the words “International Standard” appear, referring to this standard, they should be read as “Section of BS 684”. A British Standard does
9、not purport to include 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
10、 front cover, pages i and ii, pages 1 to 4, 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. Cross-references International StandardCorrespondi
11、ng British Standard ISO 661:1980BS 684 Methods of analysis of fats and fatty oils Part 0:1982 General introduction Appendix B (Identical) ISO 5555:1983BS 627:1982 Methods for sampling animal and vegetable fats and oils (Technically equivalent) Amendments issued since publication Amd. No.Date of issu
12、eComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.6:1988 BSI 10-1999i Contents Page National forewordInside front cover 1Scope and field of application1 2References1 3Definition1 4Principle1 5Reagents1 6Apparatus1 7Sampling1
13、 8Preparation of test sample1 9Procedure1 10Expression of results2 11Test report2 Figure Cooling apparatus3 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffie
14、ldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.6:1988 BSI 10-19991 1 Scope and field of application This International Standard specifies a method for the preparation of the water-insoluble fatty acids of animal and vegetable fats and oils and the determination of
15、their solidification temperature, called conventionally the titre of the fat or oil. The method is not applicable to fats and oils the titre of which is below 30 C. 2 References ISO 661, Animal and vegetable fats and oils Preparation of test sample. ISO 5555, Animal and vegetable fats and oils Sampl
16、ing. 3 Definition For the purposes of this International Standard, the following definition applies. titre constant temperature observed when there is a temporary halt in the fall in temperature or, if there is an increase in temperature, the maximum temperature reached during the cooling, with cont
17、inuous stirring, of liquid fatty acids 4 Principle Saponification of a test portion with potassium hydroxide solution in glycerol, dissolution of the soap in water and neutralization. Washing of the separated insoluble fatty acids with hot sodium chloride solution, drying and filtering. Melting of t
18、he prepared fatty acids, cooling them, with continuous stirring, and observation of the solidification temperature as shown by a halt in the fall of temperature, possibly accompanied by a temporary rise in temperature. 5 Reagents All reagents shall be of recognized analytical quality and the water u
19、sed shall be distilled water or water of at least equivalent purity. 5.1 Potassium hydroxide, solution in glycerol, prepared by dissolving 100 g of potassium hydroxide in 500 g of glycerol by heating to not more than 130 C. Foaming may occur at higher temperatures. 5.2 Sulfuric acid, solution prepar
20、ed by carefully adding 1 volume of concentrated sulfuric acid ( = 1,84 g/ml) to 4 volumes of water, while stirring. 5.3 Sodium chloride, 100 g/l solution. 5.4 Sodium sulfate, anhydrous. 5.5 Methyl orange, 5 g/l indicator solution. 6 Apparatus Usual laboratory apparatus and in particular 6.1 Flat-bot
21、tomed flask or beaker, of 1 litre capacity, made of borosilicate glass. 6.2 Electric hotplate, capable of being controlled at approximately 130 and at 140 10 C, preferably having a magnetic stirrer. 6.3 Separating funnel, of 500 ml capacity. 6.4 Cooling apparatus, fitted with an apparatus suitable f
22、or continuous stirring (see the Figure). 6.4.1 Wide-necked jar, of height 130 mm and external diameter 100 mm. 6.4.2 Test tube, 100 mm 25 mm, fitted with a stirrer that can be operated continuously and move through a vertical distance of about 40 mm. The test tube may be marked at a height of 55 mm.
23、 The stirrer shall be made of glass or inert metal 2 to 3 mm in diameter, with the bottom end bent to form a complete circle 19 mm in diameter in the horizontal plane. 6.4.3 Flat cork, to fit the jar (6.4.1) and with a central hole to support the test tube (6.4.2). 6.4.4 Thermometer, graduated in 0,
24、1 C divisions, calibrated for the temperature range within which the titre falls and suitable to be suspended so that the bulb is about 10 mm from the bottom of the test tube (6.4.2). 6.5 Water (or other liquid) bath, capable of being maintained at a temperature 20 to 25 C below the expected titre.
25、7 Sampling See ISO 5555. 8 Preparation of test sample Prepare the test sample in accordance with ISO 661. 9 Procedure 9.1 Preparation of fatty acids insoluble in water Weigh about 110 g of the potassium hydroxide solution (5.1) into the 1 litre flask or beaker (6.1). Stir and heat on the hot plate (
26、6.2) to about 130 C. Add about 45 g of the test sample (clause 8) heated to about 60 C. Stir the mixture on the hotplate, controlled at 140 10 C, until the saponification is complete, as indicated by the mixture becoming transparent and homogeneous with the formation of a foam persisting for a few m
27、inutes when stirring and heating are stopped. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.6:1988 2 BSI 10-1999 Allow the temperature to drop to about 105 C. Add 300 ml of hot water, with stirring. Stir and heat (to boiling if ne
28、cessary) until the soap is completely dissolved. Add the sulfuric acid solution (5.2), usually about 50 ml, with stirring, until the mixture is neutral to methyl orange (5.5). Continue heating and stirring until the fatty acids form a clear liquid surface layer. NOTEIf short-chain fatty acids are pr
29、esent, heat the acidified mixture under reflux. Transfer the hot mixture to the separating funnel (6.3). Draw off and reject the aqueous layer. Wash the fatty acids with three 150 ml portions of the sodium chloride solution (5.3) which is hot enough to maintain the fatty acids in a liquid state. Aft
30、er each washing, draw off the aqueous layer as completely as possible and reject it. Transfer the fatty acids to a 100 ml beaker, add approximately 5 g of the anhydrous sodium sulfate (5.4) and stir. Filter through a dry filter paper, ensuring that the fatty acids remain liquid. 9.2 Determination of
31、 titre Heat the fatty acids (9.1) to about 10 C above the expected titre. Pour into the test tube (6.4.2) to a height of 55 mm, assemble the cooling apparatus (6.4) and place it in the bath (6.5). Immediately operate the stirrer at a rate of 80 to 100 complete up-and-down motions per minute. Observe
32、 the temperature which, after a rapid initial decrease, falls slowly as crystallization starts and then becomes constant or rises within 30 s. Stop the stirring. Record to the nearest 0,1 C either the constant temperature or the maximum temperature reached in any rise as the titre. 9.3 Number of det
33、erminations Carry out a two determinations (9.2) on the same prepared fatty acids (9.1). 10 Expression of results 10.1 Method of calculation Take as the result the arithmetic mean of the two determinations (9.3), provided that the requirements for repeatability (10.2) are met. Otherwise carry out tw
34、o more determinations on the same prepared fatty acids (9.1). Express the result to the nearest 0,1 C. 10.2 Repeatability The difference between the values of two determinations carried out in rapid succession by the same analyst on the same prepared fatty acids shall not exceed 0,2 C. NOTEThe figur
35、e of 0,2 C has been accepted historically in several countries. Recent tests have not shown any reason to disagree with this Figure. 11 Test report The test report shall show the method used and the result obtained. It shall also mention any operating conditions not specified in this International S
36、tandard or regarded as optional, as well as any circumstances that may have influenced the result. The test report shall include all details required for the complete identification of the sample. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c)
37、BSI BS 684-1.6:1988 BSI 10-19993 Figure Cooling apparatus Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 4 blank Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.6:1988 BSI
38、10-1999 Publications referred to See national foreword. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 684-1.6: 1988 ISO 935:1988 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national
39、body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions British Standards are updated by amendment or revision. Users of British Standards should make sure that they possess the la
40、test amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which
41、 can be found on the inside front cover. Tel: 020 8996 9000. Fax: 020 8996 7400. BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards. Buying standards Orders for all BSI, international and foreign standar
42、ds publications should be addressed to Customer Services. Tel: 020 8996 9001. Fax: 020 8996 7001. In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as British Standards, unless otherwise requested. Information on st
43、andards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service. Various BSI electronic information services are also available which give details on all its products and services. Contact the Informat
44、ion Centre. Tel: 020 8996 7111. Fax: 020 8996 7048. Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards. For details of these and other benefits contact Membership Administration. Tel: 020 8996 7002. Fax: 020
45、 8996 7001. Copyright Copyright subsists in all BSI publications. BSI also holds the copyright, in the UK, of the publications of the international standardization bodies. Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system
46、 or transmitted in any form or by any means electronic, photocopying, recording or otherwise without prior written permission from BSI. This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols, and size, type or grade designations. If thes
47、e details are to be used for any other purpose than implementation then the prior written permission of BSI must be obtained. If permission is granted, the terms may include royalty payments or a licensing agreement. Details and advice can be obtained from the Copyright Manager. Tel: 020 8996 7070. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:19 GMT+00:00 2006, Uncontrolled Copy, (c) BSI