1、 Reference number ISO 418:2001(E) ISO 2001INTERNATIONAL STANDARD ISO 418 Third edition 2001-12-15 Photography Processing chemicals Specifications for anhydrous sodium sulfite Photographie Produits chimiques de traitement Spcifications relatives au sulfite de sodium anhydre ISO 418:2001(E) PDF discla
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4、 file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. ISO 2001 All rig
5、hts 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 th
6、e 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 reserved ISO 418:2001(E) ISO 2001 All rights reserved iiiContents Page Foreword.iv Introduction.v 1 Sco
7、pe 1 2 Normative references1 3 General1 3.1 Physical properties1 3.2 Hazardous properties1 3.3 Storage1 4 Requirements.2 5 Reagents and glassware.2 6 Sampling.2 7 Test methods .2 7.1 Assay 2 7.2 Mass fraction of insoluble matter (as a precipitate of calcium, magnesium and ammonium hydroxides) 5 7.3
8、Mass fraction of heavy metals .5 7.4 Mass fraction of iron .5 7.5 Alkalinity (as Na 2 CO 3 )5 7.6 Reaction to ammoniacal silver nitrate.6 7.7 Mass fraction of thiosulfate (as Na 2 S 2 O 3 )6 7.8 Appearance of solution.7 Table 1 Summary of requirements .2 ISO 418:2001(E) iv ISO 2001 All rights reserv
9、ed Foreword ISO (the International Organization for Standardization) is a worldwide 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
10、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 (IEC) on all matt
11、ers of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the 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 Standar
12、d 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 Standard may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. International
13、 Standard ISO 418 was prepared by Technical Committee ISO/TC 42, Photography. This third edition cancels and replaces the second edition (ISO 418:1994), of which it constitutes a technical revision. ISO 418:2001(E) ISO 2001 All rights reserved vIntroduction This International Standard is one of a se
14、ries that establishes criteria of purity for chemicals used in processing photographic materials. General test methods 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 analytica
15、l 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 and, in some cases, other protective apparel such as rubber gloves, fa
16、ce masks or aprons. Normal precautions for the safe performance of any chemical procedure shall be exercised at all times, 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 detai
17、ling 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. This International Standard provides chemical and physical requirements for the suitability of a photographic-grade chemic
18、al. The tests correlate with undesirable photographic effects. Purity requirements are set as low as possible consistent with these photographic effects. These criteria are considered to be the minimum requirements necessary to assure sufficient purity for use in photographic processing solutions, e
19、xcept 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 purity requirements have been set to take advantage of the availability of the higher-quality material. Every effort has been made to ke
20、ep 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 samples “as received” to reflect the condition of materials furnished for use. Although the ultimate criterion for suitability of such a chemical is i
21、ts 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 a
22、s a 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 in clause 4 are mandatory. The physical appearan
23、ce 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 capable of being run in any normally equipped laboratory and, whenever possible, to avoid tests that require highly specialized equipment or tec
24、hniques. Instrumental methods have been specified only as alternative methods or alone in those cases where no other 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
25、precision, they may be used in place of the tests described in this International Standard. Correlation of such alternative 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 requir
26、ement states “to pass test”, however, alternative methods shall not be used. INTERNATIONAL STANDARD ISO 418:2001(E) ISO 2001 All rights reserved 1Photography Processing chemicals Specifications for anhydrous sodium sulfite 1 Scope This International Standard establishes criteria for the purity of ph
27、otographic-grade anhydrous sodium sulfite and specifies the tests to be used to determine the purity. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequ
28、ent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements 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 l
29、atest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 10349-1:1992, Photography Photographic-grade chemicals Test methods Part 1: General. ISO 10349-3:1992, Photography Photographic-grade chemicals Test
30、methods Part 3: Determination of matter insoluble in ammonium hydroxide solution. ISO 10349-5:1992, Photography Photographic-grade chemicals Test methods Part 5: Determination of heavy metals and iron content. ISO 10349-7:1992, Photography Photographic-grade chemicals Test methods Part 7: Determinat
31、ion of alkalinity or acidity. ISO 10349-9:1992, Photography Photographic-grade chemicals Test methods Part 9: Reaction to ammoniacal silver nitrate. 3 General 3.1 Physical properties Anhydrous sodium sulfite (Na 2 SO 3 ) is a white granular powder. It has a relative molecular mass of 126,04. 3.2 Haz
32、ardous properties Anhydrous sodium sulfite is not hazardous when handled with normal precautions. Avoid contact with acids. 3.3 Storage Anhydrous sodium sulfite shall be stored in a closed container at room temperature. ISO 418:2001(E) 2 ISO 2001 All rights reserved 4 Requirements A summary of the r
33、equirements is shown in Table 1. Table 1 Summary of requirements Test Limit Subclause International Standard in which test method is given Assay Minimum: 97,0 % 7.1 ISO 418 Insoluble matter (as precipitate of calcium, magnesium and ammonium hydroxides) Maximum: 0,5 % 7.2 ISO 10349-3 Mass fraction of
34、 heavy metals (as Pb) Maximum: 0,002 % 7.3 ISO 10349-5 Mass fraction of iron (Fe) Maximum: 0,005 % 7.4 ISO 10349-5 Alkalinity (as Na 2 CO 3 ) Maximum: 0,15 % 7.5 ISO 10349-7 Reaction to ammoniacal silver nitrate To pass test 7.6 ISO 10349-9 Mass fraction of thiosulfate (as Na 2 S 2 O 3 ) Maximum: 0,
35、03 % 7.7 ISO 418 Appearance of solution Clear and free from insoluble matter except for a slight flocculence 7.8 ISO 418 5 Reagents and glassware All reagents, materials and glassware shall conform to the requirements specified in ISO 10349-1 unless otherwise noted. The hazard warning symbols, used
36、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 labelling requirements, as these vary from country to country. 6 Sampling See ISO 10349-1. 7 Test
37、methods 7.1 Assay 7.1.1 Specification The minimum mass fraction of anhydrous sodium sulfite shall be 97,0 %. ISO 418:2001(E) ISO 2001 All rights reserved 37.1.2 Reagents 7.1.2.1 Hydrochloric acid, HCI, r 1,18 g/ml (DANGER: BC) 1) . 7.1.2.2 Potassium iodide, KI. 7.1.2.3 Iodine, c(I 2 ) = 0,05 mol/l (
38、12,7 g/l) 2)3) . Weigh, to the nearest 0,001 g, 12,7 g of freshly sublimed iodine (DANGER: CO) into a tared weighing flask. Add 36 g of potassium iodide (7.1.2.2) and 100 ml of water. After solution is complete, add three drops of hydrochloric acid (7.1.2.1) (DANGER: BC), and dilute to 1 litre at 20
39、 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 = 7.1.2.4 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 the direct-titration method (7.1.4.2). 7.1.2.5 Salicylic
40、acid, c(HOC 6 H 4 COOH) = 1 % (10 g/l). 7.1.2.6 Starch indicator, 5 g/l solution. Stir 5 g of soluble starch into 100 ml of 1 % salicylic acid solution (7.1.2.5). Add 300 ml to 400 ml of boiling water. Boil until the starch dissolves and dilute to 1 litre with water. 7.1.3 Apparatus 7.1.3.1 Burette,
41、 of capacity 50 ml. 7.1.3.2 Pipette, of capacity 50 ml. 7.1.3.3 Magnetic stirrer and bar, for the direct-titration method (7.1.4.2). 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), trans
42、fer 50,00 ml of the iodine solution (7.1.2.3) to a glass-stoppered flask. Weigh, to the nearest 0,000 1 g, a test portion of about 0,25 g and wash this into the flask. Add 5 ml of the hydrochloric acid (7.1.2.1) (DANGER: BC) and using a burette (7.1.3.1) titrate with the sodium thiosulfate solution
43、(7.1.2.4), adding 2 ml of the starch indicator (7.1.2.6) just before the endpoint. 1) Hazard warning codes are defined in ISO 10349-1. 2) Commercially available analysed reagent solution is recommended. If the solution is to be prepared, see any quantitative analytical chemistry test. 3) It is recom
44、mended that self-prepared iodine solutions be standardized before use. ISO 418:2001(E) 4 ISO 2001 All rights reserved 7.1.4.2 Direct-titration method Weigh, to the nearest 0,000 1 g, a test portion of about 0,16 g. Using a pipette (7.1.3.2), transfer 50,00 ml of the iodine solution (7.1.2.3) to a co
45、mpletely 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 decolourized after a
46、ddition 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 (7.1.2.6). Using a burette (7.1.3.1), immediately titrate with the iodine solution to the first perma
47、nent light-purple colour. Wash any iodine solution remaining on the burette tip into the solution with deionized water. If the titration exceeds 10 ml, repeat the test as this can result in test results lower than the actual assay. Adjust the sample appropriately. 7.1.5 Expression of results 7.1.5.1
48、 Back-titration method The assay, expressed as a percentage by mass of sodium sulfite (Na 2 SO 3 ), is given by ( ) ( ) 12 6,302 100ccV m - where c 1 is the actual concentration, expressed in moles per litre, of the iodine solution (7.1.2.3); c 2 is the actual concentration, expressed in moles per l
49、itre, of the sodium thiosulfate solution (7.1.2.4); V is the volume, expressed in millilitres, of the sodium thiosulfate solution used for the titration in 7.1.4.1; m is the mass, expressed in grams, of the test portion; 6,302 is the conversion factor obtained from the equivalent mass of sodium sulfite (i.e. 126,04/2) the conversion factor for millilitres to litres (i.e. 0,001) 100 (for percentage); 100 is the conversion factor obtained from the volume, expressed in milli
