ISO INTERNATIONAL STANDARD 420 Second edition 1994-10-15 Photography - Processing chemicals Specifications for potassium bromide Photographie - Produits chimiques de traitement - Spécifications pour le bromuredepotassium ISO Reference number ISO420:1994(E) No reproduction or networking permitted without license from IHS Not for Resale ISO 420:1994(E) Foreword ISo (the International C Organization for Standardization) is a worldwide preparing International Standards is normally carried out through IsO technical committees. Each member body interested in a subject for which atechnical 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 (IEC) 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 Standard requires approval by at least 75 % of the member bodies casting a vote. ISO/TC 42, Photography. This second edition cancels and replaces the first edition (ISO 420:1976), which has been technically revised. ISO1994 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced microfilm, without permission in writing from the publisher. International Organization for Standardization Casepostale56:CH-1211Geneve20:Switzerland Printed in Switzerland ational Organization for Standardization No reproduction or networking permitted without license from IHS Not for Resale ISO 420:1994(E) @ISO Introduction 0.1 This International Standard is one of a series that establishes criteria of purity for chemicals used in processing photographic materials. General compiled in parts 1, 3, 5, 6, 7, 8 and 10 of ISO 10349. working knowledge of analytical techniques, which may not always be the 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 apparel such as face masks or aprons where appropriate. Normal precautions required in the performance of any chemical procedure are to hazardousmaterials.Hazard warnings designatedby aletter enclosed in 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- 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 the higher-quality material. Every effort has been made to keep the number of requirements to a minimum. Inert impurities are limited to amounts which will not unduly reduce the assay. All tests are performed on samples "as received" to reflect the condition of materials furnished for use.Althoughthe ultimatecriterionforsuitabilityof sucha chemical is 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 methodisavailable.Aneffectiveassayrequirementservesnotonlyasa safeguard of chemical purity but also as a valuable complement to the identity test. Identity tests have been included whenever a possibility exists that another chemical or mixture of chemicals could pass the other tests. All requirements listed