1、Reference number ISO 3629:2000(E) ISO 2000 INTERNATIONAL STANDARD ISO 3629 Third edition 2000-12-15 Photography Processing chemicals Specifications for potassium metabisulfite Photographie Produits chimiques de traitement Spcifications relatives au mtadisulfite de potassiumISO 3629:2000(E) PDF discl
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5、ghts 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 either ISO at the address below or ISOs member body in the country of t
6、he requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.ch Web www.iso.ch Printed in Switzerland ii ISO 2000 All rights reservedISO 3629:2000(E) ISO 2000 All rights reserved iii Contents Page Foreword.iv Introduction.v 1 S
7、cope 1 2 Normative references 1 3 General1 3.1 Physical properties1 3.2 Hazardous properties1 3.3 Storage1 4 Requirements.1 5 Reagents and glassware.2 6 Sampling.2 7 Test methods2 7.1 Assay 2 7.2 Mass fraction of heavy metals4 7.3 Mass fraction of iron .5 7.4 Reaction to ammoniacal silver nitrate.5
8、7.5 pH value5 7.6 Mass fraction of thiosulfate (as S 2 O 3 2 ) 5 7.7 Appearance of solution.6ISO 3629:2000(E) iv ISO 2000 All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of prep
9、aring 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
10、liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft Internat
11、ional 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. Attention is drawn to the possibility that some of the elements of this International S
12、tandard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 3629 was prepared by Technical Committee ISO/TC 42, Photography. This third edition cancels and replaces the second edition (ISO 3629:1996), of whi
13、ch it constitutes a technical revision.ISO 3629:2000(E) ISO 2000 All rights reserved v Introduction This International Standard is one of a series that establishes criteria of purity for chemicals used in processing photographic materials. General test methods and procedures cited in this Internatio
14、nal Standard are compiled in ISO 10349-1. This International Standard is intended for use by individuals with a 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 t
15、he handling of chemicals requires the use of safety glasses or goggles and, in some cases, other protective apparel such as rubber gloves, face masks or aprons. Normal precautions for the safe performance of any chemical procedure must be exercised at all times, but specific details have been provid
16、ed for hazardous materials. Hazard warnings designated by a letter enclosed in angle brackets “ ” a r eu s e da sa 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 f
17、rom the manufacturer. This International Standard provides chemical and physical requirements 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. T
18、hese criteria are considered to be the minimum requirements necessary to ensure 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
19、use, the purity requirements have been set to take advantage of the availability of the higher-quality material. Every effort has been made to keep the number of requirements to a minimum. Inert impurities are limited to amounts that will not unduly reduce the assay. All tests are performed on sampl
20、es “as received” to reflect the condition of materials furnished for use. Although the ultimate criterion for suitability of such a chemical is its successful performance in an appropriate use test, the shorter, more economical test methods described in this International Standard are generally adeq
21、uate. 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 identity test. Identity tests have been included whenever a possibility exists t
22、hat 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 footnotes are for general information only and are not part of the requirements. Efforts have been made to employ tests that are
23、 capable of being run in any normally equipped laboratory and, wherever possible, to avoid tests that require highly specialized equipment or techniques. Instrumental methods have been specified only as alternative methods or alone in those cases where no other satisfactory method is available. Over
24、 the past few years, great improvements have been made in instrumentation for various analyses. Where such techniques have equivalent or greater precision, they may be used in place of the tests described in this International Standard. Correlation of such alternative procedures with the given metho
25、d is the responsibility of the user. In the case of disagreement in results, the method called for in the specification should prevail. Where a requirement states “to pass test”, however, alternative methods should not be used.INTERNATIONAL STANDARD ISO 3629:2000(E) ISO 2000 All rights reserved 1 Ph
26、otography Processing chemicals Specifications for potassium metabisulfite 1 Scope This International Standard establishes criteria for the purity of photographic-grade potassium metabisulfite and specifies the tests to be used to determine the purity. 2 Normative references The following normative d
27、ocuments contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are en
28、couraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO
29、 10349-1:1992, Photography Photographic-grade chemicals Test methods Part 1: General. ISO 10349-5:1992, Photography Photographic-grade chemicals Test methods Part 5: Determination of heavy metals and iron content. ISO 10349-9:1992, Photography Photographic-grade chemicals Test methods Part 9: Reacti
30、on to ammoniacal silver nitrate. 3 General 3.1 Physical properties Potassium metabisulfite (K 2 S 2 O 5 ) exists in the form of white, glassy crystals. It has a relative molecular mass of 222,33. 3.2 Hazardous properties Potassium metabisulfite is not hazardous when handled with normal precautions,
31、but it is toxic if ingested. Avoid contact with acids. 3.3 Storage Potassium metabisulfite shall be stored in a closed container at room temperature. 4 Requirements A summary of the requirements is shown in Table 1.ISO 3629:2000(E) 2 ISO 2000 All rights reserved Table 1 Summary of requirements Test
32、Limit Subclause International Standard in which test method is given Assay Minimum: 95,0 % 7.1 ISO 3629 Mass fraction of heavy metals (as Pb) Maximum: 0,005 % 7.2 ISO 10349-5 Mass fraction of iron (Fe) Maximum: 0,005 % 7.3 ISO 10349-5 Reaction to ammoniacal silver nitrate To pass test 7.4 ISO 10349-
33、9 pH value 3,7 to 4,6 7.5 ISO 3629 Mass fraction of thiosulfate (as S 2 O 3 2 ) Maximum: 0,04 % 7.6 ISO 3629 Appearance of solution Clear and free from insoluble matter except for a slight flocculence 7.7 ISO 3629 5 Reagents and glassware All reagents, materials and glassware shall conform to the re
34、quirements specified in ISO 10349-1 unless otherwise noted. The hazard warning symbols, used as a reminder in those steps detailing handling operations, are defined in ISO 10349-1. These symbols are used to provide information to the user and are not meant to provide conformance with hazardous label
35、ling requirements, as these vary from country to country. 6 Sampling See ISO 10349-1. 7 Test methods 7.1 Assay 7.1.1 Specification The minimum mass fraction of potassium metabisulfite shall be 95,0 %. 7.1.2 Reagents 7.1.2.1 Acetic acid, glacial,CH 3 COOH (DANGER: B C ) 1) . 7.1.2.2 Acetic acid, c(CH
36、 3 COOH) 2mol /l . Dilute 120 g of glacial acetic acid (7.1.2.1) (DANGER: B C ) to 1 litre. 7.1.2.3 Hydrochloric acid (HCl), 1,18 g/ml (DANGER: B C ). 7.1.2.4 Potassium iodide (KI). 1) Hazard warning codes are defined in ISO 10349-1.ISO 3629:2000(E) ISO 2000 All rights reserved 3 7.1.2.5 Iodine, c(I
37、 2 ) = 0,05 mol/l (12,7 g/l) 2) 3) . Weigh, to the nearest 0,001 g, 12,7 g of freshly sublimed iodine (DANGER: C O ) into a tared weighing flask. Add 36 g of potassium iodide (7.1.2.4) and 100 ml of water. After solution is complete, add three drops of hydrochloric acid (7.1.2.3) (DANGER: B C ) and
38、dilute to 1 litre at 20 C in a volumetric flask. From the mass of iodine, m, calculate the concentration, c, in moles per litre, from 254 m c 7.1.2.6 Salicylic acid, c(HOC 6 H 4 COOH)=1%(10g/l). 7.1.2.7 Starch indicator, 5 g/l solution. Stir 5 g of soluble starch into 100 ml of 1 % salicylic acid so
39、lution (7.1.2.6). Add 300 ml of this solution to 400 ml of boiling water. Boil until the starch dissolves and dilute to 1 litre with water. 7.1.2.8 Sodium thiosulfate, c(Na 2 S 2 O 3 ) = 0,100 mol/l (15,8 g/l) 2) . 7.1.2.9 Sulfuric acid, c(H 2 SO 4 ) = 0,05 mol/l (4,9 g/l) 2) 4) . 7.1.2.10 Ethanol (
40、C 2 H 5 OH), 95 % (denatured). 7.1.2.11 Phenolphthalein indicator, 5 g/l solution. Dissolve 1 g of phenolphthalein in 100 ml of ethanol (7.1.2.10) and add 100 ml of water with constant stirring. Filter if necessary. 7.1.2.12 Neutral formaldehyde, c(HCHO) 37 % (360 g/l) (DANGER: B C S ). Adjust the p
41、H of the formaldehyde solution so that it is neutral to phenolphthalein indicator (7.1.2.11). 7.1.3 Apparatus 7.1.3.1 Burette, of capacity 50 ml. 7.1.3.2 Pipette, of capacity 50 ml. 7.1.4 Procedure Using a pipette (7.1.3.2), transfer 50,00 ml of the iodine solution (7.1.2.5) to a flask. Weigh, to th
42、e nearest 0,000 1 g, a test portion of about 0,23 g and wash this into the flask. Add 5 ml of the acetic acid (7.1.2.2) and mix to ensure complete dissolution of the sample. Using a burette (7.1.3.1), titrate with the sodium thiosulfate solution (7.1.2.8), adding 2 ml of the starch indicator (7.1.2.
43、7) just before the endpoint. Weigh, to the nearest 0,001 g, another test portion of about 5 g. Dissolve it in 50 ml of water and add 50 ml of the neutral formaldehyde (7.1.2.12). Add a few drops of the phenolphthalein indicator (7.1.2.11) and, using a burette (7.1.3.1), titrate with the sulfuric aci
44、d (7.1.2.9) to the colour change. 2) Commercially available analysed reagent solution is recommended. If the solution is to be prepared, see any quantitative analytical chemistry text. 3) It is recommended that self-prepared iodine solutions be standardized before use. 4) This can be prepared from c
45、oncentrated sulfuric acid, 1,84 g/ml (DANGER: C ).ISO 3629:2000(E) 4 ISO 2000 All rights reserved 7.1.5 Expression of results The assay, expressed as a percentage by mass of potassium metabisulfite (K 2 S 2 O 5 ), is given by 122 33 12 5,558 100 11 ,12 ccV cV mm where c 1 is the actual concentration
46、, expressed in moles per litre, of the iodine solution (7.1.2.5); c 2 is the actual concentration, expressed in moles per litre, of the sodium thiosulfate solution (7.1.2.8); c 3 is the actual concentration, expressed in moles per litre, of the sulfuric acid (7.1.2.9); V 2 is the volume, expressed i
47、n millilitres, of the sodium thiosulfate solution used for the first titration in 7.1.4; V 3 is the volume, expressed in millilitres, of the sulfuric acid used for the second titration in 7.1.4; m 1 is the mass, expressed in grams, of the test portion used for the first titration; m 2 is the mass, e
48、xpressed in grams, of the test portion used for the second titration; 5,558 is the conversion factor obtained from the equivalent mass of potassium metabisulfite (i.e. 222,33/4) the conversion factor for millilitres to litres (i.e. 0,001) 100 (for percentage); 100 is the conversion factor obtained f
49、rom the volume, expressed in millilitres, of the iodine solution added in 7.1.4 (i.e. 50) the number of equivalents of the iodine solution (i.e. 2); 11,12 is the conversion factor obtained from the equivalent mass of potassium metabisulfite (i.e. 222,33/4) the number of equivalents of potassium metabisulfite for potassium sulfite (i.e. 2) the conversion factor for millilitres to litres (i.e. 0,001) 100 (for percentage). NOTE When an assay base
