ISO INTERNATIONAL STANDARD 424 Second edition 1994-10-15 Photography - Processing chemicals : Specifications for anhydrous sodium carbonate and sodium carbonate monohydrate Photographie - Produits chimiques de traitement - Spécifications pour le carbonate de sodium anhydre et monohydraté ISO Reference number ISO424:1994(E) n for Standardizatior e with ISd No reproduction or networking permtted withoutlicense from IHS Not for Resale ISO 424:1994(E) Foreword 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, governmental 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 International a vote. International Standard ISO 424 was prepared by Technical Committee ISO/TC 42, Photography. This second edition cancels and replaces the first edition (ISO 424:1976) and ISO 3942:1976. ?ISO1994 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher International Organization for Standardization Case postale 56 : CH-1211 Geneve 20 : Switzerland Printed in Switzerland ii No reproduction or networking permited without license from IHS Not for Resale @ ISO ISO 424:1994(E) Introduction 0.1 This International Standard is one of a series that establishes criteria compiled in parts 1, 5, 6 and 9 of ISO 10349. This International Standard is intended for use by individuals with a case. Some of the procedures utilize caustic, toxic or otherwise hazardous chemicals. Safe laboratory practice for the handling of chemicals requires the use of safety glasses or goggles, rubber gloves and other protective precautions required inthe performance ofany chemicalprocedureareto hazardousmaterials.Hazard warnings designatedby aletter enclosed in angle brackets, < >, are used as a reminder in those steps detailing handling operations and are defined in isO 10349-1. [ More detailed information regarding hazards, handling and use of these chemicals may be available from the manufacturer. 0.2 This International Standard provides chemical and physical re- quirements for the suitability of a photographic-grade chemical. The tests correlate with undesirable photographic effects. Purity requirements are set as low as possible consistent with these photographic effects. These criteria are considered the minimum requirements necessary to assure sufficient purity for use in photographic processing solutions, except that if the purity of a commonly available grade of chemical exceeds photographic processing requirements and if there is no economic penalty in its use, the number of requirements to a minimum. Inert impurities are limited to amounts which will not unduly reduce the assay. All tests are performed use.Althoughthe ultimatecriterionforsuitabilityofsuchachemicalis its successful performance in an appropriate use test, the shorter, more economical test methods described' in this International Standard are generally adequate. Assay procedures have been included in all cases where a satisfactory method is available. An effective assay requirement serves not only as a safeguard of chemical purity but also as a valuable complement to the exists that another chemical or mixture of chemicals could pass the other tests. All requirements listed in clause 4 are mandatory. The physical appearance of the material and any foot