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1、BRITISH STANDARD BS 6049-6: 1988 ISO 1577:1987 Methods of test for tea Part 6: Determination of acid-insoluble ash ISO title: Tea Determination of acid-insoluble ash UDC 663.95:543.822:543.832 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI
2、BS 6049-6:1988 This British Standard, having been prepared under the direction of the Food and Agriculture Standards Committee, was published under the authority of the Board of BSI and comes into effect on 30 June 1988 BSI 12-1999 First published December 1980 First revision June 1988 The following
3、 BSI references relate to the work on this standard: Committee reference FAC/8 Draft (ref. 87/53372) announced in BSI News September 1987 ISBN 0 580 16623 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Food and Agriculture Standards C
4、ommittee (FAC/-) to Technical Committee FAC/8, upon which the following bodies were represented: Department of Trade and Industry (Laboratory of the Government Chemist) Ministry of Agriculture, Fisheries and Food Overseas Development Natural Resources Institute Paper Sack Development Association Ltd
5、. Tea Producers Association United Kingdom Tea Association Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-6:1988 BSI 12-1999i Contents Page Committees responsibleInsi
6、de front cover National forewordii 1Scope and field of application1 2References1 3Definition1 4Principle1 5Reagents1 6Apparatus1 7Procedure1 8Expression of results1 9Test report2 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:04 GMT+00:00 2006,
7、 Uncontrolled Copy, (c) BSI BS 6049-6:1988 ii BSI 12-1999 National foreword This Part of BS 6049 has been prepared under the direction of the Food and Agriculture Standards Committee. It supersedes the 1981 edition of BS 6049-6, which is withdrawn, and implements an agreement, to which the UK was a
8、party, reached in Subcommittee 8, Tea, of Technical Committee TC 34, Agricultural food products, of the International Organization for Standardization (ISO). The UK also provides the secretariat for the Subcommittee. This Part of BS 6049 is identical with ISO 1577:1987 “Tea Determination of acid-ins
9、oluble ash”. The principal difference between this Part of BS 6049 and the 1981 edition is that it is now considered that silica dishes are unsuitable for use with the test. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British
10、 Standard without deviation. 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 a
11、s the decimal marker. The symbol “l” 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 “Part of BS 6049”. Additional inform
12、ation. With reference to clause 5, water complying with grade 3 of BS 3978:1987 “Specification for water for laboratory use” is suitable. This standard describes a method of test only and should not be referred to as a specification defining limits of purity. Reference to the standard should indicat
13、e that the method of test used is in accordance with BS 6049-6. 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 with a British Standard does not of itself confer immunity f
14、rom legal obligations. Cross-references International StandardCorresponding British Standard BS 6049 Methods of test for tea ISO 1572:1980Part 1:1981 Preparation of ground sample of known dry matter content (Identical) ISO 1575:1987Part 4:1988 Determination of total ash (Identical) Summary of pages
15、This document comprises a front cover, an inside front cover, pages i and ii, pages 1 and 2, 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. L
16、icensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-6:1988 BSI 12-19991 1 Scope and field of application This International Standard specifies a method for the determination of the acid-insoluble ash from tea. 2 References ISO 1572, Tea P
17、reparation of ground sample of known dry matter content. ISO 1575, Tea Determination of total ash. 3 Definition For the purposes of this International Standard, the following definition applies. acid-insoluble ash the part of the total ash, obtained in accordance with ISO 1575, remaining after treat
18、ment with hydrochloric acid solution under the conditions specified in this International Standard 4 Principle Treatment of the total ash with hydrochloric acid solution, filtration, ignition and weighing of the residue. 5 Reagents All reagents shall be of recognized analytical grade. The water used
19、 shall be distilled water or water of equivalent purity. 5.1 Hydrochloric acid solution Dilute 1 volume of concentrated hydrochloric acid (20 1,16 to 1,18 g/ml) with 2,5 volumes of water. WARNING Concentrated hydrochloric acid is corrosive, has an irritant vapour and causes burns. 5.2 Silver nitrate
20、, approximately 17 g/l solution. 6 Apparatus Usual laboratory apparatus, and the following items: 6.1 Dish, of capacity 50 to 100 ml, made of platinum, porcelain or other material unaffected by the conditions of the test, used for the determination of total ash. NOTEIt is considered that silica dish
21、es are unsuitable for use with this test. 6.2 Furnace, capable of being controlled at 525 25 C. 6.3 Boiling water bath 6.4 Filter paper, ashless. 6.5 Desiccator, containing an efficient desiccant. 6.6 Analytical balance 7 Procedure 7.1 Test portion See ISO 1575. 7.2 Determination To the total ash ob
22、tained as described in ISO 1575, contained in the dish (6.1), add 25 ml of the hydrochloric acid solution (5.1). Cover the dish with a watch glass to prevent spattering, and boil gently the solution for 10 min. Allow to cool and filter the contents of the dish through the filter paper (6.4). Wash th
23、e dish and the filter paper with hot water until the washings are free from the acid, as confirmed by the silver nitrate solution (5.2). Return the filter paper and contents to the dish, evaporate the water carefully on the boiling water bath (6.3) and heat in the furnace (6.2), controlled at 525 25
24、 C, until the residue is free from visible carbon particles. Cool the dish in the desiccator (6.5) and weigh. Heat again in the furnace for 30 min, allow to cool and weigh; repeat these operations, if necessary, until the difference between two successive weighings does not exceed 0,001 g. Note the
25、lowest mass. 7.3 Number of determinations Carry out two separate determinations on the residues obtained from the two determinations of total ash. 8 Expression of results 8.1 Method of calculation and formula The acid-insoluble ash obtained from the ground sample, expressed as a percentage by mass o
26、n the dry basis, is equal to where m0is the mass, in grams, of the test portion of the ground sample used for the determination of total ash (see ISO 1575); m3is the mass, in grams, of the acid-insoluble ash; RSis the dry matter content, as a percentage by mass, of the ground sample, determined by t
27、he method specified in ISO 1572. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-6:1988 2 BSI 12-1999 Take as the result the arithmetic mean of the two determinations, provided that the requirement for repeatability (see 8.2) is sati
28、sfied. 8.2 Repeatability The difference between the results of two determinations, carried out simultaneously or in rapid succession by the same analyst, shall not exceed 0,02 g of acid-insoluble ash per 100 g of ground sample. 9 Test report The test report shall show the method used and the result
29、obtained. It shall also mention any operating details not specified in this International Standard, or regarded as optional, as well as any circumstances that may have influenced the result. The report shall include all details required for complete identification of the sample. Licensed Copy: sheff
30、ieldun sheffieldun, na, Wed Dec 06 13:37:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-6:1988 BSI 12-1999 Publications referred to See national foreword. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:37:04 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-6: 1988 ISO 1577:1987 B
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