ISO INTERNATIONAL STANDARD 1577 Second edition 1987-10-01 INTERNATIONALORGANIZATION FORSTANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEKAYHAPOAHAAOPTAHM3ALMHOCTAHAAPTW3ALMW Tea - Determination of acid-insoluble ash The-Déterminationdescendresinsolublesdans/'acide Referencenumber ISO 1577: 1987 (E) No reproduction or networking permitted 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 ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard ISO 1577 was prepared by Technical Committee ISO/Tc 34, Agricultural food products. This second edition cancels and replaces the first edition (IS0 1577 : 1980), clause 6 of which has been the subject of 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 Not for Resale ISO1577 :1987 (E) INTERNATIONALSTANDARD Tea - Determination of acid-insoluble ash 1 Scope and field of application 6 Apparatus This International Standard specifies a method for the deter- Usual laboratory apparatus, and the following items : mination of the acid-insoluble ash from tea. 6.1 Dish, of capacity 50 to 100 ml, made of platinum, porcelain or other material unaffected by the conditions of the 2 References test, used for the determination of total ash. ISo 1572, Tea - Preparation of ground sample of known dry NOTE - It is considered that silica dishes are unsuitable for use with matter content. this test. ISo 1575, Tea - Determination of total ash. 6.2 Furnace, capable of being controlled at 525 ± 25 oC. 6.3 Boiling water bath. 3 Definition 6.4 Filter paper, ashless. For the purposes of this International Standard, the following definition applies. 6.5 Desiccator, containing an efficient desiccant. acid-insoluble ash.: The part of the total ash, obtained in ac- cordance with ISo1575, remaining after treatment with 6.6 Analytical balance. hydrochloric acid solution under the conditions specified in this International Standard. 7 Procedure 4Principle 7.1 Test portion SeeISO1575 Treatment of the total ash with hydrochloric acid solution, filtration, ignition and weighing of the residue. 7.2 Determination 5 Reagents To the total ash obtained as described in IS0 1575, contained in the dish (6.1), add 25 ml of the hydrochloric acid solution (5.1). All reagents shall be of recognized analytical grade. The water Coverthe dishwitha watchglasstoprevent spattering,and used shall be distilled water or water of equivalent purity. boil gentlythe solutionfor10 min.Ailowto cool and filterthe contents of the dish through the filter paper (6.4). Wash the dish and the filter paper with hot water until the washings are 5.1 Hydrochloric acid solution. free from the acid, as confirmed by the silver nitrate solution (5.2). Return the filter paper and contents to the dish, Dilute 1 volume of concentrated hydrochloric acid (@2o 1,16 to evaporate the water carefully on the boiling water bath (6.3) 1,18 g/ml) with 2,5 volumes of water. and heat in the furnace (6.2),