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1、BRITISH STANDARD BS 6986-4: 1990 ISO 7514:1990 Analysis of instant tea Part 4: Method for determination of total ash Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-4:1990 This British Standard, having been prepared under the directi
2、on of the Agriculture and Food Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 30 November 1990 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference AFC/8 Draft for comment 89/52868 DC ISBN 0 580
3、19213 X Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Agriculture and Food Standards Policy Committee (AFC/-) to Technical Committee AFC/8, upon which the following bodies were represented: Campden Food and Drink Research Association D
4、epartment of Trade and Industry (Laboratory of the Government Chemist) Ministry of Agriculture, Fisheries and Food Natural Resources Institute Tea Producers Association United Kingdom Tea Association Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na,
5、 Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-4:1990 BSI 12-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Normative references1 3Definition1 4Principle1 5Reagent1 6Apparatus1 7Sampling1 8Preparation of the test sample1 9Procedure1
6、 10Expression of results2 11Precision2 12Test report2 Publication(s) referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-4:1990 ii BSI 12-1999 National foreword This Part of BS 6986 has been prepared under th
7、e direction of the Agriculture and Food Standards Policy Committee. It implements an agreement, to which the UK was a 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
8、 secretariat for the Subcommittee. This Part of BS 6986 is identical with ISO 7514:1990 “Instant tea in solid form Determination of total ash”. 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 i
9、ndicate that the method of test used is in accordance with BS 6986-4. 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 immu
10、nity from legal obligations. Cross-references International StandardCorresponding British Standard ISO 7513:1990 BS 6986 Analysis of instant tea Part 3:1990 Method for determination of moisture content (loss in mass at 103 C) (Identical) ISO 7516:1984Part 1:1988 Methods of sampling (Identical) Summa
11、ry 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 fr
12、ont cover. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-4:1990 BSI 12-19991 1 Scope This International Standard specifies a method for the determination of the total ash of instant tea in solid form. 2 Normative references The fol
13、lowing standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this International Standard are en
14、couraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 7513:1990, Instant tea in solid form Determination of moisture content (loss in mass at 103 C). ISO
15、 7516:1984, Instant tea in solid form Sampling. 3 Definition For the purposes of this International Standard, the following definition applies. total ash the residue obtained after treatment with hydrochloric acid and incineration at 550 C 25 C under the conditions specified in this International St
16、andard 4 Principle Destruction of organic matter by treatment with concentrated hydrochloric acid solution and heating at 550 C. Weighing of the residue. 5 Reagent 5.1 Hydrochloric acid, concentrated solution (20 = 1,16 g/ml to 1,18 g/ml), of recognized analytical grade. WARNING Concentrated hydroch
17、loric acid solution is corrosive, has an irritant vapour and causes burns; it shall be handled in accordance with good laboratory practice. 6 Apparatus Usual laboratory apparatus and, in particular, the following. 6.1 Dish, of approximately 50 ml capacity, made of platinum, porcelain or any other ma
18、terial unaffected by the conditions of the test. 6.2 Furnace, capable of being controlled at 550 C 25 C. 6.3 Hot-plate, thermostatically controlled. 6.4 Desiccator, containing an efficient desiccant. 7 Sampling Sampling shall have been carried out in accordance with ISO 7516. 8 Preparation of the te
19、st sample Thoroughly mix the instant tea sample as received by shaking or inverting the sealed sample container. 9 Procedure 9.1 Preparation of the dish Ensure that the dish (6.1) is completely clean, and then heat it in the furnace (6.2) at 550 C 25 C for at least 30 min. Cool in the desiccator (6.
20、4). After cooling to room temperature, weigh to the nearest 0,001 g. 9.2 Test portion Open the sample container and immediately weigh, to the nearest 0,001 g, about 2 g of the prepared test sample (clause 8) into the prepared dish (9.1). Spread the sample evenly over the base of the dish. 9.3 Determ
21、ination Add, drop by drop, to the test portion contained in the dish (9.2), sufficient (approximately 1 ml) of the concentrated hydrochloric acid solution (clause 5) to wet it completely. Place the dish on the cool hot-plate (6.3), set the control to medium and heat for 30 min. Raise the hot-plate t
22、emperature to the highest setting in three successive steps, allowing the test portion to heat at each stage for 30 min. Keep the test portion at the highest setting until no fuming has occurred for at least 5 min. Place the dish containing the test portion in the furnace (6.2) at 550 C 25 C for 16
23、h. Remove, leave to cool and add a few drops of water to moisten and disperse the ash. Evaporate to dryness on the hot-plate (6.3) as before, and then return to the furnace (6.2) for a further 30 min. Remove, cool to room temperature in the desiccator (6.4) and weigh to the nearest 0,001 g. Determin
24、e the mass of the total ash to the nearest 0,001 g. NOTE 1Instant tea ashed under these conditions should give a grey/white ash. 9.4 Number of determinations Carry out two determinations on the same test sample. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontro
25、lled Copy, (c) BSI BS 6986-4:1990 2 BSI 12-1999 10 Expression of results The total ash, expressed as a percentage by mass of the sample on a dry basis, is given by the formula where Take as the result the arithmetic mean of the two determinations, provided that the requirement for repeatability (see
26、 11.1) is satisfied. 11 Precision 11.1 Repeatability For a total ash content within the range of 10 % (m/m) to 22 % (m/m), the difference between the values of two determinations, carried out in rapid succession (or simultaneously) by the same operator using the same apparatus on the same test sampl
27、e, shall not exceed 0,4 % (absolute value). 11.2 Reproducibility For a total ash content within the range of 10 % (m/m) to 22 % (m/m), the difference between the values of the final result obtained by two laboratories using this method for the analysis of the same laboratory sample, shall not exceed
28、 1,2 % (absolute value). 12 Test report The test report shall specify the method used and the result obtained. It shall also mention all operating details not specified in this International Standard, or regarded as optional, together with details of any incidents which may have influenced the resul
29、t. The test report shall include all information necessary for the complete identification of the sample. m0is the mass, in grams, of the test portion; m1is the mass, in grams, of the total ash; RSis the dry matter content, expressed as a percentage by mass, of the test sample. It is equal to 100 mi
30、nus the moisture content determined using the method specified in ISO 7513. m1 m0 - -100 100 RS - - Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 13:36:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6986-4:1990 BSI 12-1999 Publication(s) referred to See national foreword. Licensed Copy: s
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