BS-6049-7-1981 ISO-1578-1975.pdf

BRITISH STANDARD BS 6049-7: 1981 ISO 1578:1975 Methods of test for tea Part 7: Determination of alkalinity of water-soluble ash ISO title: Tea Determination of alkalinity of water-soluble ash UDC 663.95:543.822:543.241.2 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:26:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-7:1981 This British Standard, having been prepared under the direction of the Food and Agriculture Standards Committee, was published under the authority of the Executive Board and comes into effect on 31 December 1980 © BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference FAC/8 Draft for comment 73/52373 DC ISBN 0 580 11818 5 Cooperating organizations The Food and Agriculture Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following: Agricultural Co-operation and Marketing Services Agricultural Research Council, Meat Research Institute British Food Manufacturing Industries Research Association British Industrial Biological Research Association Ltd. Campden Food Preservation Research Association Consumer Standards Advisory Committee of BSI Department of Agriculture and Fisheries for Scotland Department of Agriculture (Government of Northern Ireland) Department of Industry (Laboratory of the Government Chemist)* Flour Milling and Baking Research Association Food and Drink Industries Council Food Manufacturers Federation Incorporated Institute of Brewing Local Authorities Co-ordinating Body of Trading Standards Ministry of Agriculture, Fisheries and Food* National Farmers Union National Farmers Union of Scotland Tobacco Advisory Council The organizations marked with an asterisk in the above list, together with the following, were directly represented on the Technical Committee entrusted with the preparation of this British Standard: British Tea Producers Association Overseas Development Administration Tropical Products Institute Tea Trade Committee Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:26:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-7:1981 © BSI 12-1999i Contents Page Cooperating organizationsInside front cover National forewordii 1Scope and field of application1 2References1 3Definition1 4Principle1 5Reagents1 6Procedure1 7Expression of results1 8Test report1 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:26:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-7:1981 ii © BSI 12-1999 National foreword This Part of this British Standard implements an agreement, in which the UK has taken part, reached in Subcommittee 8, Tea, of Technical Committee 34, Agricultural food products, of the International Organization for Standardization (ISO). The UK also provides the secretariat for the subcommittee. This standard is identical with ISO 1578:1975 “Tea Determination of alkalinity of water-soluble ash”. 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 Standards; attention is especially drawn to the following. Wherever the words “International Standard” appear, referring to this standard, they should be read as “British Standard”. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. 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-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 1575:1980Part 4:1981 Determination of total ash (Identical) ISO 1576:1975Part 5:1981 Determination of water-soluble ash and water-insoluble ash (Identical) Summary of pages 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. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:26:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-7:1981 © BSI 12-19991 1 Scope and field of application This International Standard specifies a method for the determination of the alkalinity of water-soluble ash of tea. 2 References ISO 1572, Tea Preparation of ground sample of known dry matter content. ISO 1575, Tea Determination of total ash. ISO 1576, Tea Determination of water-soluble ash and water-insoluble ash. 3 Definition For the purpose of this International Standard, the following definition applies: alkalinity of the water-soluble ash either the amount of acid required to neutralize the aqueous extract of the total ash, or the amount of alkali equivalent to this acid, when determined under the conditions specified 4 Principle Titration of the filtrate from the determination of water-soluble ash, with standard hydrochloric acid solution, using methyl orange as indicator. 5 Reagents 5.1 Hydrochloric acid, 0,1 N standard volumetric solution (see note to 7.1.1). 5.2 Methyl orange indicator, containing 0,5 g of methyl orange per litre. 6 Procedure 6.1 Test portion Use the filtrate obtained from the determination specified in ISO 1576. 6.2 Determination Cool the test portion and titrate it with the hydrochloric acid solution (5.1), using the methyl orange indicator (5.2). Carry out two determinations using the filtrate obtained from two determinations of water-soluble ash and water-insoluble ash. 7 Expression of results 7.1 Method of calculation and formulae Express the alkalinity in terms of milliequivalents, i.e. of the number of millilitres of normal acid required per 100 g of ground sample (see ISO 1572), on the dry basis, or as a percentage by mass of potassium hydroxide (KOH) in the ground sample, on the dry basis. 7.1.1 The alkalinity of the water-soluble ash, expressed as milliequivalents per 100 g of ground sample, on the dry basis, is given by the formula where Vis the volume, in millilitres, of 0,1 N hydrochloric acid solution required (see note below); m0is the mass, in grams, of the test portion of the ground sample used for the determination of total ash (see ISO 1575); RSis the dry matter content, as a percentage by mass, of the ground sample, determined in accordance with ISO 1572. NOTEIf the standard volumetric solution used is not of exactly the strength indicated in 5.1, a suitable correction factor should be used in calculating the results. 7.1.2 The alkalinity of the water-soluble ash, expressed as a percentage by mass of potassium hydroxide, in the ground sample, on the dry basis, is given by the formula where V, m0 and RS have the same meanings as in 7.1.1. 7.1.3 Take as the result the arithmetic mean of the two determinations. 8 Test report The test report shall show the method used and the result obtained, indicating clearly the mode of expression adopted. 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: sheffieldun sheffieldun, na, Wed Dec 06 13:26:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 2 blank Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:26:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-7:1981 © BSI 12-1999 Publications referred to See national foreword. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:26:34 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6049-7: 1981 ISO 1578:1975 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national 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 latest amendments or editions. It is the constant aim of BSI to improve the quality of our products and services. 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