BS 6049-6-1988 Methods of test for tea - Determination of acid-insoluble ash《茶叶试验方法 第6部分 酸不溶灰分含量测定》.pdf

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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 663.95:543.822:543.832BS6049-6:1988 This British Standard, having been prepared under the directionof the Food and Agriculture Sta

2、ndards Committee,was published underthe authority of the BoardofBSI and comesintoeffecton 30June1988 BSI 12-1999 First publishedDecember1980 First revisionJune1988 The following BSI references relate to the work on this standard: Committee reference FAC/8 Draft (ref. 87/53372) announced inBSI News S

3、eptember1987 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 Committee (FAC/-) to Technical Committee FAC/8, upon which the following bodies were represented: Department of Trade and Indu

4、stry (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 Comment

5、sBS6049-6:1988 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 Reagents 1 6 Apparatus 1 7 Procedure 1 8 Expression of results 1 9 Test report 2 Publications referred to Inside

6、back coverBS6049-6:1988 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 It supersedes the1981 edition of BS6049-6, which is withdrawn, and implements an agreement, to which the UK was a party, reached in Subc

7、ommittee8, 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 ISO1577:1987 “Tea Determination of acid-insoluble ash”. The principal

8、 difference between this Part of BS6049 and the1981 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 Standard without deviation.

9、 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 as the decimal marker. The sy

10、mbol “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 BS6049”. Additional information. With reference to clau

11、se5, water complying with grade3 of BS3978:1987 “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 indicate that the method of test used i

12、s in accordance with BS6049-6. 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 from legal obligations. Cross-refe

13、rences International Standard Corresponding British Standard BS 6049 Methods of test for tea ISO 1572:1980 Part 1:1981 Preparation of ground sample of known dry matter content (Identical) ISO 1575:1987 Part 4:1988 Determination of total ash (Identical) Summary of pages This document comprises a fron

14、t cover, an inside front cover, pagesi andii, pages1 and2, 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.BS6049-6:1988 BSI 12-1999 1 1 Scope

15、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 Preparation of ground sample of known dry matter content. ISO 1575, Tea Determination of total ash. 3 Definition For the purposes of this Inter

16、national Standard, the following definition applies. acid-insoluble ash the part of the total ash, obtained in accordance with ISO1575, remaining after treatment with hydrochloric acid solution under the conditions specified in this International Standard 4 Principle Treatment of the total ash with

17、hydrochloric acid solution, filtration, ignition and weighing of the residue. 5 Reagents All reagents shall be of recognized analytical grade. The water used shall be distilled water or water of equivalent purity. 5.1 Hydrochloric acid solution Dilute1 volume of concentrated hydrochloric acid ( 201,

18、16 to1,18g/ml) with2,5 volumes of water. WARNING Concentrated hydrochloric acid is corrosive, has an irritant vapour and causes burns. 5.2 Silver nitrate, approximately17g/l solution. 6 Apparatus Usual laboratory apparatus, and the following items: 6.1 Dish, of capacity50 to100ml, made of platinum,

19、porcelain or other material unaffected by the conditions of the test, used for the determination of total ash. NOTEIt is considered that silica dishes are unsuitable for use with this test. 6.2 Furnace, capable of being controlled at525 25 C. 6.3 Boiling water bath 6.4 Filter paper, ashless. 6.5 Des

20、iccator, containing an efficient desiccant. 6.6 Analytical balance 7 Procedure 7.1 Test portion See ISO1575. 7.2 Determination To the total ash obtained as described in ISO1575, contained in the dish (6.1), add25ml of the hydrochloric acid solution (5.1). Cover the dish with a watch glass to prevent

21、 spattering, and boil gently the solution for10min. Allow to cool and filter the contents of the dish through the filter paper (6.4). Wash the 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 pape

22、r and contents to the dish, evaporate the water carefully on the boiling water bath (6.3) and heat in the furnace (6.2), controlled at525 25 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 for30min, allow to cool

23、and weigh; repeat these operations, if necessary, until the difference between two successive weighings does not exceed0,001g. Note the 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 r

24、esults 8.1 Method of calculation and formula The acid-insoluble ash obtained from the ground sample, expressed as a percentage by mass on the dry basis, is equal to where m 0 is the mass, in grams, of the test portion of the ground sample used for the determination of total ash (seeISO1575); m 3 is

25、the mass, in grams, of the acid-insoluble ash; RS is the dry matter content, as a percentage by mass, of the ground sample, determined by the method specified in ISO1572.BS6049-6:1988 2 BSI 12-1999 Take as the result the arithmetic mean of the two determinations, provided that the requirement for re

26、peatability (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 analyst, shall not exceed0,02g of acid-insoluble ash per100g of ground sample. 9 Test report The test report shall show the met

27、hod 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 any circumstances that may have influenced the result. The report shall include all details required for complete identification of the samp

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