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1、INTERNATIONAL STANDARD INTERNATIONAL ORGANKATION FOR STANDARDIZATIOM ORGANISATION INTERNATIONALE DE NORMALISATION lvlEX)JYHAPOHAR OPTAHM3AMfl l-l0 CTAHflAPTL13AMM Tea - Determination of total ash TM - Determination des cendres totales ISO 1575 Third edition 1987-10-01 Reference number ISO 1575 : 198
2、7 (E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national Standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Esch member body interested in a subject for whi
3、ch a technical committee has been established has the right to be represented on that committee. International organizations, govern- mentaland non-governmental, in liaison with ISO, also take part in the work. Draft International Standards adopted by the technical committees are circulated to the m
4、ember bodies for approval before their acceptance as International Standards by the ISO Council. They are approved in accordance with ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard ISO 1575 was prepared by Technical Committee ISO/TC 34, Agricultur
5、al food produc ts. This third edition cancels and replaces the second edition (ISO 1575 : 19801, of which it constitutes a minor revision. Users should note that all International Standards undergo revision from time to time and that any reference made herein to any other International Standard impl
6、ies its latest edition, unless otherwise stated. 0 International Organkation for Standardkation, 1987 Printed in Switzerland -,-,- INTERNATIONAL STANDARD ISO 1575 : 1987 (E) Tea - Determination of total ash 1 Scope and field of application This International Standard specifies a method for the deter
7、mi- nation 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 asb and wa ter-insoluble ash. ISO 1577, Tea - Determination of acid-insoluble ash. 3 Definition For the purposes of this Interna
8、tional Standard, the following definition applies. total ash : The residue obtained after incineration at 525 + 25 OC under the conditions specified in this Inter- national Standard. 4 Principle Destruction of organic matter by heating at 525 + 25 OC to constant mass. 5 Apparatus Usual laboratory ap
9、paratus, and the following items : 5.1 Dish, of capacity 50 to 100 ml, made of platinum, porce- lain or other material unaffected by the conditions of the test. NOTE - It is considered that silica dishes are unsuitable for use with this test. 5.2 Furnace, capable of being controlled at 525 + 25 OC.
10、5.3 Steam bath. 5.4 Hot-plate. 5.5 Desiccator, containing an eff icient desiccant. 5.6 Analytical balance. 6 Sample Use a ground Sample of known dry matter content, prepared as specified in ISO 1572. 7 Procedure 7.1 Preparation of the dish Heat the dish (5.1) for 1 h in the furnace (5.2) at 525 + 25
11、 OC. Cool in the desiccator (5.5). After cooling, weigh to the nearest 0,001 g. 7.2 Test Portion Weigh, to the nearest 0,001 g, about 5 g of the ground Sample into the prepared dish (7.1). (See ISO 1572.) 7.3 Determination 7.3.1 Heat the test Portion in the dish, at a temperature near 100 OC until t
12、he moisture is expelled. Transfer the dish to the furnace (5.2) and heat at 525 rt 25 OC until the ash is visibly free from carbon particles (at least 2 h 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 hot-plate (5.4). R
13、eturn the dish to the furnace for 60 min, cool in the desiccator and weigh. Heat again in the furnace for 30 min, cool and weigh. Repeat these operations, if necessary, until the differente between two successive weighings does not exceed 0,001 g. 7.3.2 Reserve the total ash for determination of wat
14、er-soluble asb and water-insoluble ash (see ISO 1576), or of acid-insoluble ash (see ISO 15771, if required. 7.4 Number of determinations Carry out two separate determinations on the same ground Sample (clause 6). 1 -,-,- ISO 1575 : 1987 (El 8 Expression of results 8.1 Method of calculation and form
15、ula The total ash yielded by the ground Sample, expressed as a per- centage by mass on the dry basis, is given by the formula 100 100 rnl x - x - m. RS where m. is the mass, in grams, of the test Portion; ml is the mass, in grams, of the total ash; RS is the dry matter content, as a percentage by ma
16、ss, of the ground Sample, determined in accordance with ISO 1572. Take as the result the arithmetic mean of the two determina- tions, provided that the requirement for repeatability (see 8.2) is satisf ied. 8.2 Repeatability The differente between the results of two determinations, car- ried out sim
17、ultaneously or in rapid succession by the same analyst, shall not exceed 0,2 g of total ash per 100 g of ground Sample. 9 Test report The test report shall show the method used and the result obtained. lt shall also mention any operating details not speci- fied 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 identifi- cation of the Sample. UDC 663.95 : 543.822 Descriptors : agricultural products, tea, tests, ash determination. Price based on 2 pages 2 -,-,-
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