ISO INTERNATIONAL STANDARD 7834 Firstedition 1987-12-15 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION SO ORGANISATION INTERNATIONALE DE NORMALISATION Iron ores - Determination of arsenic content Molybdenum blue spectrophotometric method Minerais de fer - Dosage de I'arsenic -- Methode spectrophotometrique au bleu de molybdene Referencenumber ISO 7834 : 1987 (B) Copyvihtlntematioal Organizatin fr Standardization No reproduction or networking permited 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 mental and non-governmentai, in liaison with Iso, aiso 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 1SO 7834 was prepared by Technical Committee ISO/TC 102, Ironores. 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 Not for Resale ISO7834 :1987 (E) INTERNATIONAL STANDARD Iron ores Determination of arsenic content Molybdenum blue spectrophotometric method WARNING -- Attention is drawn to the toxic nature of arsenic and its solutions and of other reagents used in this method and to the need to take particular care in the handling and disposal of solutions. Scope and field of application 4 Reagents This International Standard specifies a molybdenum blue spec- During the analysis, use only, reagents of recognized analytical trophotometric method for the determination of the arsenic grade, and only deionized water or water of equivalent purity. content of iron ores. NOTE -- In order to obtain reliable values at the lowest levels of This method is applicable to a concentration range of o0,o00 1 to arsenic content in test samples (< 20μg/g),reagents should be 0,1 % (m/m) (T to 1 000 μg/g) of arsenic in natural iron ores, selected or purified so that the value for the absorbance of the blank and iron ore concentrates and agglomerates including sinter test measured in a cell of 20 mm optical path length is not greater than 0,025, equivalent to 1 μg of arsenic. In particular, nitric acid may need products. to be redisilled, or the apparatus cleaning procedures (5.2) may need to be applied more rigorously. 2. References 4.1 Sodium peroxide(Na202),fine powder. ISo 648, Laboratory glassware -- One-mark pipettes. ISo 1042, Laboratory glassware - One-mark volumetric 4.2 Potassium bromide (KBr). flasks. Iso3081,Iron ores-Increment sampling--Manual method. 4.3 Hydrazine sulfate (N2H4.H2SO4). Iso 3082, Iron ores - Increment sampling and sample prepar- 4.4 Hydrochloric acid (g 1,16 to 1,19 g/ml). ation-Mechanicalmethod. Iso3083,Iron ores- Preparation of samples - Manual 4.5 Nitric acid (o 1,4 g/ml), diluted 1 + 1. method. ISo 7764, lron ores -Preparation of predried test samples for 4.6Sulfuric acid (o 1,84 g/ml), free from phosphorus. chemicalanalysis. 4.7 Ammonium molybdate [(NH4)sMo7024:4H20], solu- 3Principle tion, 10 g/l. To. 400 ml of water in a 1 litre beaker, add carefully, with stir- Decomposition of a test portion by sintering with sodium peroxide and leaching with water and hydrochloric acid. ring, 133 ml of sulfuric acid (4.6). Cool, add 10 ± 0,1 g of am monium molybdate and dissolve with stirring. Transfer to a Transfer of the solution to a distillation flask, evaporation of 1