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1、W 4851903 0572699 9T5 INTERNATIONAL STANDARD IS0 11427:1993 TECHNICAL CORRIGENDUM 1 Published 1994-11-15 INTERNATIONAL OROANUATION FOR STANDARDIUTION- MEXAYHAPOAHAR OPrAHH3AlWR Il0 CTAHAAPTHSAUHCI. ORGANISATION INTERNATWALE DE NORMALISATION Determination of silver in silver jewellery alloys - Volume
2、tric (potentiometric) method using potassium bromide TECHNICAL CORRIGENDUM 1 Dosage de largent dans les alliages dargent pour la bijouterie-joaillerie - Mthode volumtrique (potenriomtrique) utilisant le bromure de potassium RECTIFICATIF TECHNIQUE 1 Technical corrigendum 1 to International Standard I
3、S0 11427:1993 was prepared by Technical Committee ISOflC 174, Jewellery. Page 1 Subclause 4.2 Replace 1 mol/l by 0 , l mol/l. WDC 671.12.01469.225.543.24:546.293 Ref. No. IS0 11427:1993/Cor.l:1994(E) Dexripton: jewellev, silver alloys, chemical analysis, determination of content, silver, volumetric
4、analysis, metal assay. 0 IS01994 Printed in Swiizerland IS0 33427 93 = 4853903 0535404 439 W I N T E i? NAT I O NA L IS0 STANDARD 11427 First edition 1993-05-01 Determination of silver in silver jewellery alloys - Volumetric (potentiometric) method using potassium bromide Dosage de largent dans les
5、alliages dargent pour la bijouterie-joaillerie - Mthode volumtrique (potentiomtrique) utilisant le bromure de potassium Reference number IS0 1 1427:1993(E) IS0 33427 93 m 4853903 0535405 355 m IS0 11427:1993(E) Foreword IS0 (the International Organization for Standardization) is a worldwide federati
6、on of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 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
7、. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the techni
8、cal 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. International Standard IS0 1 1427 was prepared by Technical Committee ISO/TC 174, Jewe/ery. Q IS0 1993 Ali rights reserved.
9、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 per- mission in writing from the publisher. International Organization for Standardization Case Postale 56 CH-1211 Genve 20 Switzerland Print
10、ed in Switzerland ii IS0 11427 93 m 4851903 0535406 291 m INTERNATIONAL STANDARD IS0 11427:1993(E) Determination of silver in silver jewellery alloys - Volumetric (potentiometric) method using potassium - bromide 1 Scope This International Standard specifies a volumetric method for the determination
11、 of silver in silver jewel- lery alloys, preferably within the range of fineness stated in IS0 9202. These alloys may contain copper, zinc, cadmium and palladium. Apart from palladium, which must be pre- cipitated before commencing titration, these el- ements do not interfere with this method of det
12、ermination. NOTE 1 This method is intended to be used as the ref- eree method for the determination of fineness in the alloys covered by IS0 9202. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this International Stand
13、ard. At the time of publi- cation, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most re- cent edition of the standard indicated below. Mem- bers of
14、IEC and IS0 maintain registers of currently valid International Standards. IS0 9202:1991, Jewellery - Fineness o f precious metal alloys. 3 Principle The sample is dissolved in dilute nitric acid. The silver content of the resulting solution is determined by titration with standard potassium bromide
15、 solution, using a potentiometric indication of the equivalence point. 4 Reagents During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only dis- tilled water or water of equivalent purity. 4.1 Nitric acid, 33 % Wm), p20 = 1,2 g/cm3, free of halide. 4.2 P
16、otassium bromide, solution, c(KBr) = 1 mol/. Dissolve 11,90 g of potassium bromide (dried at 105 O C ) in water and dilute to 1 litre. 4.3 Disodium dimethylglyoxime octahydrate, solution. Dissolve 1 O g of disodium dimethylglyoxime octa- hydrate in l O00 ml of water. 4.4 Silver, minimum purity 999,9
17、 parts by mass per thousand (%o). 5 Apparatus Ordinary laboratory apparatus and 5.1 Motor-driven plunger or piston-type burette, linked to a potentiometer or automatic titrator and capable of delivering increments of 0,05 ml at the equivalence point. 5.2 Titration apparatus, with combination silver
18、electrode coated with silver bromide and Hg/Hg2S04 or other suitable reference electrode. 6 Sampling The sampling procedure for silver and silver alloys shall be agreed upon until a standard method has been published. 1 IS0 11427 93 4851903 0535407 128 = IS0 11427:1993(E) For coated articles, approp
19、riate precautions that have been agreed upon shall be taken, to exclude the coating from the determination. 7 Procedure 7.1 Test portion The test portion used for the titratio between 300 mg and 500 mg of weighed to an accuracy of 0,Ol mg. shall contain Iver and be 7.2 Determination of the potassium
20、 bromide factor The factor determinations should not differ from each other by more than 0,05 parts by mass per hundred (%) relative value. The mean value, FI shall be used in subsequent calculations for maximum accuracy. The potassium bromide factor shall be determined immediately before analysis o
21、f the test portions. 7.3 Determination 7.3.1 Preparation of the test solution Weigh between 300 mg and 500 mg of the test por- tion (7,1), to the nearest 0,OI mg, and transfer to a glass beaker. Add 5 ml of nitric acid (4.1) and warm gently to dissolve the alloy. Heat to drive off nitrogen oxides. 7
22、.3.2 Elimination of palladium 7.2.1 Preparation of silver standards Weigh three samples of silver (4.41, each of 300 mg to 500 mg, accurately to the nearest 0,Ol mg, and transfer them into three glass beakers. Add 5 mI of nitric acid (4.1) to each beaker, and warm gently to dissolve the silver. Heat
23、 until the evolution of nitrogen oxides ceases. Cool, by dilution to about 100 ml with water, and transfer to the titration apparatus (5.2). NOTE 2 The mass of the standard silver samples should lie within 20 mg of the mass of silver in the test portions (7.1). 7.2.2 Titration of the standard silver
24、 solution Add, via the plunger-burette (5.1) and with continuous stirring, sufficient potassium bromide solution (4.2) to precipitate about 95 parts by mass per hundred (%) of the silver in the solution. Titrate the remaining silver in such a manner that the equivalence point can be interpolated fro
25、m 0,05 ml additions of the potassium bromide solution. NOTE 3 This split titration approach may be effected automatically, using an automatic titrator with so-called dy- namic volume dosing based on the measured potential dif- ference across the electrodes in the titration vessel (5.2). 7.2.3 Calcul
26、ation of the potassium bromide factor The potassium bromide factor, F, is calculated using the formula where mAs V, is the mass of silver, in milligrams; is the volume, in millilitres, of potassium bromide solution at the equivalence point. Palladium shall be eliminated by addition of an aqueous sol
27、ution of disodium dimethylglyoxime octa- hydrate (4.3). For each 100 mg of palladium, add 50 ml of this solution before commencing the titra ti on. 7.3.3 Titration of the test solution Proceed exactly as for the standard solution. It may be necessary to carry out a pilot determination to ob- tain an
28、 approximate value of the silver content. The volume of potassium bromide solution at the equival- ence point is interpolated from these measurements, 8 Expression of results 8.1 Method of calculation 8.1.1 Since the potassium bromide factor, F (7.2.31, is expressed in milligrams of silver for each
29、millilitre of solution, the mass mA , in milligrams, of silver in the test portion is calculatecf using the formula mAg = FV. 8.1.2 Calculate the silver content of the sample, wAg, in parts by mass per thousand (%O), using the formula where m, is the mass, in milligrams, of the test por- tion (7.1).
30、 8.2 Repeatability The results of duplicate determinations shall corre- spond to better than 1 part by mass per thousand (%O) of silver. If the variation is greater than this, the assays shall be repeated. 2 -,-,- IS0 11427 93 4451903 0535408 Ob4 = IS0 11427:1993(E) 9 Test report The test report sha
31、ll include the following information: a) identification of the sample including source, date of receipt, form of sample; b) sampling procedure; c) the method used by reference to this International Standard; d) silver content of the sample, in parts by mass per thousand (%o) as single values and mea
32、n values; e) if relevant, any deviations from the method speci- fied in this International Standard; f) any unusual features observed during the deter- mination; g) date of test; h) identification of the laboratory carrying out this analysis; i) signature of the laboratory manager and operator. 3 IS0 11427 73 4851703 O535409 TTO H IS0 11427:1993(E) UDC 671.12.01 4:669.225.543.24:546.293 Descriptors: jewellery, silver alloys, chemical analysis, determination of content, silver, volumetric analysis, metal assay. Price based on 3 pages