ISO INTERNATIONAL STANDARD 2598-2 First edition 1992-12-15 Iron ores --- Determination of silicon content Part 2: Reduced molybdosilicate spectrophotometric method Mineraisdefer-Dosagedusilicium Partie 2: Methode spectrophotometrique au molybdosilicate reduit Reference number ISO 2598-2:1992(E) Copyright Ilr No reproduction or networking permited without license from IHS Not for Resale ISO 2598-2:1992(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. 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. Iso collaborates closely with the International Electrotechnical Commission (lEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an Inter- national Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard Iso 2598-2 was prepared by Technical Committee Iso/TC 102, Iron ores, Sub-Committee sc 2, Chemical analysis. This part of isO 2598 cancels and replaces isO 4686:1980, of which it constitutes a technical revision. Iso 2598 consists of the following parts, under the general title Iron ores --Determination of silicon content: - Part 1: Gravimetric methods Part 2: Reduced molybdosilicate spectrophotometric method Annex A forms an integral part of this part of Iso 2598. Annexes B and C are for information only. C ISO 1992 or by any means,electronic or mechanical, Including photocopylng and mlcrotilm, without permisslon inwritingfromthepubilsher. InternatlonalOrganizatlonforStandardization CasePostale56·CH-1211Geneve20*Swltzerland Printed in Switzerland Not for Resale ISO 2598-2:1992(E) INTERNATIONAL STANDARD Iron ores --- Determination of silicon content Part 2: Reduced molybdosilicate spectrophotometric method 1 Scope Iso3083:1986,lron ores -Preparation of samples Manual method. This part of Iso 2598 specifies a reduced molybdosilicate spectrophotometric method for the Iso 7764:1985, lron ores -- Preparation of predried determination of the silicon content of iron ores. test samples for chemical analysis. This method is applicable to silicon contents be- 3 Principle tween 0,1 % (m/m) and 5.0 % (m/m) in natural iron ores, iron ore concentrates and agglomerates, in- Decomposition of the test portion by fusion with cluding sinter products, especially for ores contain- sodium tetraborate or a fusion mixture (carbonate ing fluorine. and tetraborate) and treatment with dilute nitric acid. The fluorine content of the sample does not affect the determination. Addition of ammonium molybdate to convert the silicate into a molybdosilicate complex and re- duction to molybdenum blue with ascorbic acid. Spectrophotometric measurement of the absorb- 2 Normative references ance of the molybdenum blue complex at a wave- length of approximately 600 nm. The following standards contain provisions which, through reference in this text, constitute provisions 4 Reagents of this part of iso 2598. At the time of publication the editions indicated were valid. All standards are During the analysis, use only reagents of recognized subjecttorevision,andpartiestoagreementsbased on this part of iso 2598 are encouraged to investi- analytical grade and only distilled water or water of equivalent purity. gatethepossibilityofapplyingthemostrecentedi- tions of the standards indicated below. Members of IEc and iso maintain registers of currently valid 4.1 Sodium tetraborate (Na2B,O7), anhydrous. International Standards. 4.2 Potassium nitrate (KNO3) Iso 648:1977, Laboratory glassware One-mar