NTERNATIONAL STANDARD (ISO 3705 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION -MEKIYHAPOIHA OPIAHW3ALMS HO CTAHIAPTW3ALWN.ORGANISATION INTERNATIONALE DE NORMALISATION Sulphur for industrial use - Determination of arsenic content - Silver diethyldithiocarbamate photometric method Soufre a usage industriel-Dosage de I'arsenic - Methode photometrique au diethyldithiocarbamade d'argent First edition - 1976-09-01 ISO 3705-1976 (E) UDC 661.21 : 546.19 : 543.42 Ref.No.ISO 3705-1976 (E) Descriptors:sulphur, chemicai analysis,determination of content,arsenic,spectrophotometric analysis. Price based on 2 pages FOREWORD iso (the International Organization for Standardization) is a worldwide federation of national standards institutes (Iso Member Bodies). The work of developing International Standards is carried out through ISo Technical Committees. Every Member Body interested in a subject for which a Technical Committee has been set up has the right to be represented on that Committee. International organizations, governmental and non-governmental,in liaison withiso,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 bytheisoCouncil. International Standard IsO3705 was drawn up by Technical Committee ISO/TC 47, Chemistry, and was circulated to the Member Bodies in January 1975. It has been approved by the Member Bodies of the following countries : Austria Ireland Switzerland Belgium Israel Turkey Brazil Poland United Kingdom Bulgaria Portugal U.S.S.R. France Romania Yugoslavia Germany South Africa, Rep. of India Spain No Member Body expressed disapproval of the document. international Organization for Standardization, 1976 Printed in Switzerland INTERNATIONALSTANDARD ISO3705-1976(E) Sulphur for industrial use - Determination of arsenic content - Silver diethyldithiocarbamate photometric method 1 SCOPEANDFIELDOFAPPLICATION 6 SAMPLINGANDPREPARATIONOFTESTSAMPLE This International Standard specifies a silver diethyldithio- Proceed in accordance with the appropriate International carbamate photometric method for the determination of Standard.1) the arsenic content of sulphur for industrial use. Prepare a test sample from the laboratory sample by The method is applicable to products having arsenic drying a sufficient quantity for 2 h in an oven maintained contents equal to or greater than 0,5 mg/kg. at about 8o c. After cooling in a desiccator, grind until fine enough to pass through a sieve of nominal aperture 630 μm. 2 REFERENCE ISO 2590, General method for the determination of 7PROCEDURE arsenic- Silver diethyldithiocarbamate photometric method. WARNING - Because of the toxicity and unpleasant odour of pyridine, it is recommended that it should be handled with care and in a well-ventilated fume cupboard. 3PRINCIPLE Dissolution of a test portion in carbon tetrachloride. 7.1 Test portion and preparation of test solution Oxidation by bromine and nitric acid. Weigh, to the nearest 0,1 g, about 5g of the test sample Determination of the arsenic content by the method (clause6) and place in a beaker of suitable capacity(for specified in ISO 2590. example 400 ml). In a well-ventilated fume cupboard, add 20 ml of the 4REAGENTS bromine solution(4.9).Allowto stand for45min andthen add, drop by drop, while swirling gently, 25 ml of the nitric See clause 4 of IsO 2590. acid solution (4.10).During this operation,cool thebeaker However, replace reagent 4.1 (hydrochloric acid) by in an ice/water mixture to prevent a too rapid evolution of nitrous fumes. If the oxidation of sulphur is incomplete, 4.1 Suiphuric acid, approximately 15 N solution. the operation may be repeated using a fewmillilitres of the bromine solution (4.9) and of the nitric acid solution Also, add the following reagents : (4.10). Heat in a boiling water bath to eliminate the excess 4.9 Bromine, solution containing 3 volumes of carbon bromine, car