1、Reference number ISO 3627:2001(E) ISO 2001 INTERNATIONAL STANDARD ISO 3627 Third edition 2001-12-15 Photography Processing chemicals Specifications for anhydrous sodium metabisulfite Photographie Produits chimiques de traitement Spcifications pour le mtadisulfite de sodium anhydreISO 3627:2001(E) PD
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5、 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 either ISO at the address below or ISOs member body in the count
6、ry of the 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 2001 All rights reservedISO 3627:2001(E) ISO 2001 All rights reserved iii Contents Page Foreword.iv Introductio
7、n.v 1 Scope 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 metals6 7.3 Mass fraction of iron .6 7.4 Reaction to ammoniacal silver nit
8、rate.6 7.5 pH value6 7.6 Mass fraction of thiosulfate (as S 2 O 3 2 ) 7 7.7 Appearance of solution.8 Table 1 Summary of requirements .2ISO 3627:2001(E) iv ISO 2001 All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bo
9、dies (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 organizatio
10、ns, 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. International Standards are drafted in accordance with the rules given in the
11、ISO/IEC Directives, Part 3. 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. Attention is drawn to the possibility that so
12、me of the elements of this International Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International Standard ISO 3627 was prepared by Technical Committee ISO/TC 42, Photography. This third edition cancels and replaces
13、the second edition (ISO 3627:1994), of which it constitutes a technical revision.ISO 3627:2001(E) ISO 2001 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 metho
14、ds and procedures cited in this International 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
15、 chemicals. Safe laboratory practice for the 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 shall be exercised at all t
16、imes, but specific details have been provided for hazardous materials. Hazard warnings designated by a letter 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 u
17、se of these chemicals may be available from 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, consi
18、stent with these photographic effects. These 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
19、 if there is no economic penalty in its 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
20、 assay. All tests are performed on samples “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 I
21、nternational 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 identity test. Identity tests have been
22、included whenever a possibility 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 footnotes are for general information only and are not part of the requirements. Efforts
23、 have been made to employ tests that are 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 othe
24、r satisfactory method is available. Over 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 alt
25、ernative procedures with the given method is the responsibility of the user. In case of disagreement in results, the method called for in the specification shall prevail. Where a requirement states “to pass test“, however, alternative methods shall not be used.INTERNATIONAL STANDARD ISO 3627:2001(E)
26、 ISO 2001 All rights reserved 1 Photography Processing chemicals Specifications for anhydrous sodium metabisulfite 1 Scope This International Standard establishes criteria for the purity of photographic-grade anhydrous sodium metabisulfite and specifies the tests to be used to determine the purity.
27、2 Normative references The following normative documents 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 agreem
28、ents based on this International Standard are encouraged 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
29、 of currently valid International Standards. ISO 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 Photogra
30、phic-grade chemicals Test methods Part 9: Reaction to ammoniacal silver nitrate. 3 General 3.1 Physical properties Anhydrous sodium metabisulfite (Na 2 S 2 O 5 ) exists as a white or pale-cream granular powder. It has a relative molecular mass of 190,10. 3.2 Hazardous properties Anhydrous sodium met
31、abisulfite is not hazardous when handled with normal precautions. Avoid contact with acids. 3.3 Storage Anhydrous sodium metabisulfite shall be stored in a closed container at room temperature. 4 Requirements A summary of the requirements is shown in Table 1.ISO 3627:2001(E) 2 ISO 2001 All rights re
32、served Table 1 Summary of requirements Test Limit Subclause International Standard in which test method is given Assay Minimum: 95,0 % 7.1 ISO 3627 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 ammoniaca
33、l silver nitrate To pass test 7.4 ISO 10349-9 pH value 3,7 to 4,6 7.5 ISO 3627 Mass fraction of thiosulfate (as S 2 O 3 2 ) Maximum: 0,03 % 7.6 ISO 3627 Appearance of solution Clear and free from insoluble matter except for a slight flocculence 7.7 ISO 3627 5 Reagents and glassware All reagents, mat
34、erials and glassware shall conform to the requirements 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
35、 to provide conformance with hazardous labelling 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 anhydrous sodium metabisulfite shall be 95,0 %. 7.1.2 Reagents 7.1.2.1 Acetic acid, glacial,CH 3
36、 COOH (DANGER: B C ) 1) . 7.1.2.2 Acetic acid, c(CH 3 COOH) 2mol/l. Dilute 120 g of glacial acetic acid (7.1.2.1) (DANGER: B C )to1l i tr e . 1) Hazard warning codes are defined in ISO 10349-1.ISO 3627:2001(E) ISO 2001 All rights reserved 3 7.1.2.3 Hydrochloric acid,HCI, 1,18 g/ml (DANGER: B C ). 7.
37、1.2.4 Potassium iodide,K I . 7.1.2.5 Iodine, c(I 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
38、hydrochloric acid (7.1.2.3) (DANGER: B C ) and 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 2 I 254 m c 7.1.2.6 Salicylic acid,H OC 6 H 4 COOH, 1 % (10 g/l) solution. 7.1.2.7 Starch indicator, 5 g/l solution. St
39、ir 5 g of soluble starch into 100 ml of 1 % salicylic acid solution (7.1.2.6). Add 300 ml 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) . NOTE This solution is not required for th
40、e direct-titration method (7.1.4.2). 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,C 2 H 5 OH, 95 % (denatured). 7.1.2.11 Phenolphthalein indicator,5g/l . Dissolve 1 g of phenolphthalein in 100 ml of ethanol (7.1.2.10) and add 100 ml of water with constant stirri
41、ng. Filter if necessary. 7.1.2.12 Neutral formaldehyde, HCHO, approximately 37 % (360 g/l) (DANGER: B C S ). Adjust the pH 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 m
42、l. 7.1.3.3 Magnetic stirrer and bar, for direct-titration method (7.1.4.2). 2) Commercially available analysed reagent solution is recommended. If the solution is to be prepared, see any quantitative analytical chemistry test. 3) It is recommended that self-prepared iodine solutions be standardized
43、before use. 4) This can be prepared from concentrated sulfuric acid, 1,84 g/ml (DANGER: C ).ISO 3627:2001(E) 4 ISO 2001 All rights reserved 7.1.4 Procedure Use either the back-titration method (7.1.4.1) or the direct-titration method (7.1.4.2). 7.1.4.1 Back-titration method Using a pipette (7.1.3.2)
44、, transfer 50,00 ml of the iodine solution (7.1.2.5) to a glass-stoppered flask. Weigh, to the 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), titrat
45、e with the sodium thiosulfate solution (7.1.2.8), adding 2 ml of the starch indicator (7.1.2.7) 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 pheno
46、lphthalein indicator (7.1.2.11) and, using a burette (7.1.3.1), titrate with the sulfuric acid (7.1.2.9) to the colour change. 7.1.4.2 Direct-titration method Weigh, to the nearest 0,000 1 g, a test portion of about 0,12 g. Using a pipette (7.1.3.2), transfer 50,00 ml of the iodine solution (7.1.2.5
47、) to a completely dry 250 ml beaker that contains a magnetic stirring bar (7.1.3.3). While stirring the iodine solution in the beaker, add the test portion to the centre of the beaker using a camel-hair brush. Avoid contact of the sample with the sides of the beaker. If the iodine is not decolourize
48、d after addition of the sample, discard the trial and restart the procedure. If necessary, increase the test portion by 0,01 g. Wash down the side walls of the beaker using about 2 ml of the starch indicator (7.1.2.7). Using a burette (7.1.3.1), immediately titrate with the iodine solution to the fi
49、rst permanent light-purple colour. Wash any iodine solution remaining on the burette tip into the solution with deionized water. If the titration volume exceeds 4 ml, repeat the test as this can result in test results lower than the actual assay. Adjust the sample appropriately. 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
