ISO INTERNATIONAL STANDARD 1575 Third edition 1987-10-01 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEXKAYHAPOAHAAOPTAHM3AUMANOCTAHAAPTW3ALMW Tea - Determination of total ash The--Determination des cendrestotales Referencenumber ISO 1575:1987 (E) Copyright International Organization for Standardization ermitted without license from IHS Not for Resale 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. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with iso, also take part in the work. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISo Council. They are approved in accordance with ISso procedures requiring at least 75 % approval by the member bodies voting. International Standard ISo 1575 was prepared by Technical Committee ISO/TC 34, Agricultural food products. This third edition cancels and replaces the second edition (IS0 1575 : 1980), 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 implies its latest edition, unless otherwise stated. International Organization for Standardization, 1987 Printed in Switzerland No reproduction or networking permitted without license from IHS INTERNATIONAL STANDARD ISO 1575:1987 (E) Tea -- Determination of total ash 1Scope and field of application 5.4 Hot-plate. This International Standard specifies a method for the determi- 5.5 Desiccator, containing an efficient desiccant. nation of the total ash from tea. 5.6Analytical balance. 2 References 6 Sample Iso 1572, Tea - Preparation of ground sample of known dry matter content. Use a ground sample of known dry matter content, prepared as specified in ISO 1572. ISO1576,Tea- Determination of water-soluble ash and water-insoluble ash. Procedure ISo 1577, Tea - Determination of acid-insoluble ash. 7.1 Preparation of the dish 3Definition Heat the dish (5.1) for 1 h in the furnace (5.2) at 525 ± 25 oC Cool in the desiccator (5.5). After cooling, weigh to the nearest For the purposes of this International Standard, the following 0,001 g. definition applies. 7.2 Test portion total ash : The residue obtained after incineration at 525 ± 25 oc under the conditions specified in this Inter- Weigh, to the nearest 0,001 g, about 5 g of the ground sample national Standard. into the prepared dish (7.1). (See ISO 1572.) 7.3 Determination 4 Principle 7.3.1 Heat the test portion in the dish, at a temperature near Destruction of organic matter by heating at 525 ± 25 °C to 100 oc until the moisture is expelled. Transfer the dish to the constant mass. furnace (5.2) and heat at 525 ± 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 5 Apparatus on the steam bath (5.3) and then on the hot-plate (5.4). Return the dish to the furnace for 60 min, cool in the desiccator and Usual laboratory apparatus, and the following items : weigh. Heat again in the furnace for 30 min, cool and weigh. Repeat these operations, if necessary, until the difference between two successive weighings does not exceed 0,001 g. 5.1 Dish, of capacity 50 to 100 ml, made of platinum, porce- lain or other material unaffected by the conditions of the test. 7.3.2Reservethetotalashfordeterminationofwater-soluble NOTE - It is considered that silica dishes are unsuitable for use with ash and water-insoluble ash (see IS 15