BS 6049-4-1988 Methods of test for tea - Determination of total ash《茶叶试验方法 第4部分 总灰分含量测定》.pdf

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1、BRITISH STANDARD CONFIRMED AUGUST 1992 BS 6049-4: 1988 ISO 1575:1987 Methods of test for tea Part 4: Determination of total ash ISO title: Tea Determination of total ash UDC 663.95:543.822BS6049-4:1988 This British Standard, having been prepared under the directionof the Food and Agriculture Standar

2、ds Committee,was published underthe authority of the BoardofBSI and comes into effect on 30June1988 BSI 12-1999 First published December 1980 First revision June 1988 The following BSI references relate to the work on this standard: Committee reference FAC/8 Draft (ref 87/53371) announced in BSI New

3、s September 1987 ISBN 0 580 16625 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Food and Agriculture Standards Committee (FAC/-) to Technical Committee FAC/8, upon which the following bodies were represented: Department of Trade and

4、Industry (Laboratory of the Government Chemist) Ministry of Agriculture, Fisheries and Food Overseas Development Natural Resources Institute Paper Sack Development Association Ltd. Tea Producers Association United Kingdom Tea Association Amendments issued since publication Amd. No. Date of issue Com

5、mentsBS6049-4:1988 BSI 12-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope and field of application 1 2 References 1 3 Definition 1 4 Principle 1 5 Apparatus 1 6 Sample 1 7 Procedure 1 8 Expression of results 1 9 Test report 2 Publications referred to Insid

6、e back coverBS6049-4:1988 ii BSI 12-1999 National foreword This Part of BS6049 has been prepared under the direction of the Food and Agriculture Standards Committee. It supersedes the1981 edition of BS6049-4, which is withdrawn, and implements an agreement, to which the UK was a party, reached in Su

7、bcommittee8, Tea, of Technical Committee TC34, Agricultural food products, of the International Organization for Standardization (ISO). The UK also provides the secretariat for the Subcommittee. This Part of BS6049 is identical with ISO1575:1987 “Tea Determination of total ash”. The principal differ

8、ences between this Part of BS6049 and the 1981 edition are that it is now considered that silica dishes are unsuitable for use with the test, and that vegetable oil is no longer used in the determination. Terminology and conventions. The text of the International Standard has been approved as suitab

9、le for publication as a British 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

10、 a full point on the baseline as the decimal marker. The symbol “ml” has been used to denote millilitre. In British Standards it is current practice to use the symbol “mL”. Wherever the words “International Standard” appear, referring to this standard, they should be read as “Part of BS6049”. This s

11、tandard describes a method of test only and should not be referred to as a specification defining limits of purity. Reference to the standard should indicate that the method of test used is in accordance with BS6049-4. A British Standard does not purport to include all the necessary provisions of a

12、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. Cross-references International Standard Corresponding British Standard BS 6049 Methods of test for teat ISO 1572:1980 Part

13、 1:1981 Preparation of ground sample of known dry matter content (Identical) ISO 1576:1975 Part 5:1981 Determination of water-soluble and water-insoluble ash (Identical) ISO 1577:1987 Part 6:1988 Determination of acid-insoluble ash (Identical) Summary of pages This document comprises a front cover,

14、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.BS6049-4:1988 BSI 12-1999 1 1 Scope and f

15、ield of application This International Standard specifies a method for the determination of the total ash from tea. 2 References ISO 1572, Tea Preparation of ground sample of known dry matter content. ISO 1576, Tea Determination of water-soluble ash and water-insoluble ash. ISO 1577, Tea Determinati

16、on of acid-insoluble ash. 3 Definition For the purposes of this International Standard, the following definition applies. total ash the residue obtained after incineration at525 25 C under the conditions specified in this International Standard 4 Principle Destruction of organic matter by heating at

17、525 25 C to constant mass. 5 Apparatus Usual laboratory apparatus, and the following items: 5.1 Dish, of capacity50 to100ml, made of platinum, porcelain or other material unaffected by the conditions of the test. NOTEIt is considered that silica dishes are unsuitable for use with this test. 5.2 Furn

18、ace, capable of being controlled at525 25 C. 5.3 Steam bath 5.4 Hot-plate 5.5 Desiccator, containing an efficient desiccant. 5.6 Analytical balance 6 Sample Use a ground sample of known dry matter content, prepared as specified in ISO1572. 7 Procedure 7.1 Preparation of the dish Heat the dish (5.1)

19、for 1h in the furnace(5.2) at525 25 C. Cool in the desiccator (5.5). After cooling, weigh to the nearest0,001g. 7.2 Test portion Weigh, to the nearest0,001g, about5g of the ground sample into the prepared dish (7.1). (See ISO1572.) 7.3 Determination 7.3.1 Heat the test portion in the dish, at a temp

20、erature near100 C until the moisture is expelled. Transfer the dish to the furnace (5.2) and heat at525 25 C until the ash is visibly free from carbon particles (at least2h is usually required). Allow to cool, then moisten the ash with distilled water, dry it on the steam bath (5.3) and then on the

21、hot-plate (5.4). Return the dish to the furnace for60min, cool in the desiccator and weigh. Heat again in the furnace for30min, cool and weigh. Repeat these operations, if necessary, until the difference between two successive weighings does not exceed0,001g. 7.3.2 Reserve the total ash for determin

22、ation of water-soluble ash and water-insoluble ash (see ISO1576), or of acid-insoluble ash (see ISO1577), if required. 7.4 Number of determinations Carry out two separate determinations on the same ground sample (clause6). 8 Expression of results 8.1 Method of calculation and formula The total ash y

23、ielded by the ground sample, expressed as a percentage by mass on the dry basis, is given by the formula where m 0 is the mass, in grams, of the test portion; m 1 is the mass, in grams, of the total ash; RS is the dry matter content, as a percentage by mass, of the ground sample, determined in accor

24、dance with ISO1572. Take as the result the arithmetic mean of the two determinations, provided that the requirement for repeatability (see8.2) is satisfied. 8.2 Repeatability The difference between the results of two determinations, carried out simultaneously or in rapid succession by the same analy

25、st, shall not exceed0,2g of total ash per100g of ground sample.BS6049-4:1988 2 BSI 12-1999 9 Test report The test report shall show the method used and the result obtained. It shall also mention any operating details not specified in this International Standard, or regarded as optional, as well as a

26、ny circumstances that may have influenced the result. The report shall include all details required for complete identification of the sample.BS6049-4:1988 BSI 12-1999 Publications referred to See national forewordBS 6049-4: 1988 ISO 1575:1987 BSI 389 Chiswick High Road London W4 4AL BSIBritishStand

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