1、BSI Standards PublicationBS ISO 13756:2015Jewellery Determination ofsilver in silver jewellery alloys Volumetric (potentiometric)method using sodium chlorideor potassium chlorideBS ISO 13756:2015 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 13756:2015. It su
2、persedes BS ISO 13756:1997 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee STI/53, Specifications and test methods for jewellery and horology.A list of organizations represented on this committee can be obtained on request to its secretary.This publica
3、tion does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2015.Published by BSI Standards Limited 2015ISBN 978 0 580 74805 9ICS 39.060Compliance with a British Standard cannot confer immunity from
4、 legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2015.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS ISO 13756:2015 ISO 2015Jewellery Determination of silver in silver jewellery alloy
5、s Volumetric (potentiometric) method using sodium chloride or potassium chlorideJoaillerie Dosage de largent dans les alliages dargent pour la bijouterie-joaillerie Mthode volumtrique (potentiomtrique) utilisant le chlorure de sodium ou le chlorure de potassiumINTERNATIONAL STANDARDISO13756Second ed
6、ition2015-02-01Reference numberISO 13756:2015(E)BS ISO 13756:2015ISO 13756:2015(E)ii ISO 2015 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2015All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, elec
7、tronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. +
8、41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 13756:2015ISO 13756:2015(E)Contents PageForeword ivIntroduction v1 Scope . 12 Normative references 13 Principle 14 Reagents 15 Apparatus . 26 Sampling 27 Procedure. 27.1 Determination of sodium c
9、hloride or potassium chloride standard solution factor . 27.1.1 Preparation of silver standards . 27.1.2 Titration of standard silver solution . 27.1.3 Calculation of sodium chloride or potassium chloride standard solution factor 37.2 Determination . 37.2.1 Preparation of the sample solution . 37.2.
10、2 Elimination of palladium 37.2.3 Titration of the sample solution . 38 Calculation and expression of results . 38.1 Calculation 38.2 Repeatability . 49 Test report . 4Bibliography 5 ISO 2015 All rights reserved iiiBS ISO 13756:2015ISO 13756:2015(E)ForewordISO (the International Organization for Sta
11、ndardization) 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 a technical committee has been established has the righ
12、t 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.The procedures
13、used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rule
14、s of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identif
15、ied during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on
16、the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT), see the following URL: Foreword Supplementary information .The committee responsible for this document is IS
17、O/TC 174, Jewellery.This second edition cancels and replaces the first edition (ISO 13756:1997), which has been technically revised with the following changes: addition of an analytical balance in Clause 5; change of requirement for sampling in Clause 6; addition of a warning in Clause 7 that suitab
18、le health and safety procedures should be followed; International Standard editorially revised.iv ISO 2015 All rights reservedBS ISO 13756:2015ISO 13756:2015(E)IntroductionThe following definitions apply in understanding how to implement an ISO International Standard and other normative ISO delivera
19、bles (TS, PAS, IWA): “shall” indicates a requirement; “should” indicates a recommendation; “may” is used to indicate that something is permitted; “can” is used to indicate that something is possible, for example, that an organization or individual is able to do something.ISO/IEC Directives, Part 2 (
20、sixth edition, 2011), 3.3.1 defines a requirement as an “expression in the content of a document conveying criteria to be fulfilled if compliance with the document is to be claimed and from which no deviation is permitted.”ISO/IEC Directives, Part 2 (sixth edition, 2011), 3.3.2 defines a recommendat
21、ion as an “expression in the content of a document conveying that among several possibilities one is recommended as particularly suitable, without mentioning or excluding others, or that a certain course of action is preferred but not necessarily required, or that (in the negative form) a certain po
22、ssibility or course of action is deprecated but not prohibited.” ISO 2015 All rights reserved vBS ISO 13756:2015BS ISO 13756:2015Jewellery Determination of silver in silver jewellery alloys Volumetric (potentiometric) method using sodium chloride or potassium chloride1 ScopeThis International Standa
23、rd specifies a volumetric method for the determination of silver in silver jewellery alloys, preferably within the range of fineness stated in ISO 9202. These alloys may contain copper, zinc, cadmium, and palladium. Apart from palladium, which must be precipitated before commencing titration, these
24、elements do not interfere with this method of determination.NOTE This method is an alternative recommended method to ISO 11427.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated referenc
25、es, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 11596, Jewellery Sampling of precious metal alloys for and in jewellery and associated products3 PrincipleThe sample is dissolved in dilute nitric acid. Th
26、e silver content of the resulting solution is determined by titration with standard sodium chloride or potassium chloride solution using a potentiometric indication of the equivalence point.4 ReagentsDuring the analysis, unless otherwise stated, use only reagents of recognized analytical grade and o
27、nly distilled water or water of equivalent purity.4.1 Nitric acid (HNO3), 33 % HNO3(mass fraction), with sufficiently low content of halides (check with silver nitrate test).4.2 Sodium chloride solution, c(NaCl) = 0,1 mol/l.Dissolve 5,84 g of sodium chloride (dried at 105 C) in water and dilute to 1
28、 000 ml.4.3 Potassium chloride solution, c(KCl) = 0,1 mol/l.Dissolve 7,44 g of potassium chloride (dried at 105 C) in water and dilute to 1 000 ml.4.4 Disodium dimethylglyoxime octahydrate solution.Dissolve 10 g of disodium dimethylglyoxime octahydrate in 1 000 ml of water.4.5 Silver, minimum purity
29、 999,9 parts per thousand () by mass.INTERNATIONAL STANDARD ISO 13756:2015(E) ISO 2015 All rights reserved 1BS ISO 13756:2015ISO 13756:2015(E)5 Apparatus5.1 Customary laboratory apparatus.5.2 Motor-driven plunger or piston-type burette, linked to potentiometer or automatic titrator and capable of de
30、livering increments of 0,05 ml at the equivalence point.5.3 Titration apparatus, with combination silver electrode or silver chloride coated silver electrode and Hg/Hg2SO4electrode or other suitable reference electrode.A silver chloride coating can be obtained by electrolysis, branching a silver ele
31、ctrode as anode in a dilute hydrochloric acid solution c(HCl) = 0,1 mol/l. After suitable surface preparation, apply an anodic current density of 1 mA/cm2for approximately one hour, until the silver surface is completely covered with silver chloride.5.4 Analytical balance, with a reading accuracy of
32、 0,01 mg.6 SamplingThe sampling procedure for silver and silver alloys shall be performed in accordance with ISO 11596.7 ProcedureWARNING Suitable health and safety procedures should be followed7.1 Determination of sodium chloride or potassium chloride standard solution factor7.1.1 Preparation of si
33、lver standardsWeigh, to the nearest 0,01 mg, three samples, each of 300 mg to 500 mg of silver (4.5), and transfer them to glass beakers. Add 5 ml of nitric acid (4.1) to each, and warm gently to dissolve the silver. Keep the tops of the beakers covered with watch glasses. Heat until evolution of ni
34、trogen oxides ceases. Allow to cool. Rinse the watch glasses into beakers. Transfer to the titration apparatus (5.3). Add the minimum volume of water, within the range of about 20 ml to 60 ml, to satisfy the requirements of the titration apparatus (5.3) with respect to measurement and stirring.The m
35、ass of the standard silver samples should lie within 20 mg of the mass of silver in the sample portion.7.1.2 Titration of standard silver solutionAdd, via the plunger-burette (5.2) under continuous stirring, sufficient sodium chloride standard solution (4.2) or potassium chloride standard solution (
36、4.3) to precipitate about 95 % of the silver in the solution. Titrate the remaining silver in such a manner that the equivalence point can be interpolated from 0,05 ml additions of the sodium chloride or potassium chloride standard solution.NOTE This split titration approach can be effected automati
37、cally using an automatic titrator with so called dynamic volume dosing based on the measured potential difference across the electrodes in the titration apparatus (5.3).2 ISO 2015 All rights reservedBS ISO 13756:2015ISO 13756:2015(E)7.1.3 Calculation of sodium chloride or potassium chloride standard
38、 solution factorThe sodium chloride or potassium chloride standard solution factor, F, is calculated using Formula (1)FmV=AgFAgF(1)wheremAgFis the mass of silver, in milligrams;VAgFis the volume of sodium chloride or potassium chloride solution at equivalence point, in millilitres.The factor determi
39、nations shall not differ from each other by more than 0,05 %, relative value. The mean value, F , shall be used in subsequent calculations for maximum accuracy. The sodium chloride or potassium chloride standard solution factor shall be determined immediately before analysis of the sample portions.7
40、.2 Determination7.2.1 Preparation of the sample solutionWeigh, to the nearest 0,01 mg, two sample portions, each containing between 300 mg and 500 mg of silver, and transfer them to glass beakers. Add 5 ml of nitric acid (4.1) to each and warm gently to dissolve the alloy. Keep the tops of the beake
41、rs covered with watch glasses. Heat until evolution of nitrogen oxides ceases. Allow to cool. Rinse the watch glasses into beakers. Transfer to the titration apparatus (5.3). Add water as per 7.1.1.7.2.2 Elimination of palladiumPalladium, if present, shall be eliminated by adding an aqueous solution
42、 of disodium dimethylglyoxime octahydrate (4.4). For each 100 mg of palladium, add 50 ml of this solution before commencing titration.7.2.3 Titration of the sample solutionProceed exactly as per the standard solution. It may be necessary to carry out a pilot determination to obtain an approximate va
43、lue of the silver content.8 Calculation and expression of results8.1 CalculationThe mass mAgin milligrams of silver in the sample portion is calculated using Formula (2):mFVAgsAgs= (2)whereF is the sodium chloride or potassium chloride standard solution factor, in milligrams of silver for each milli
44、litre of solution;VAgsis the volume of sodium chloride or potassium chloride at equivalence point, in millilitres. ISO 2015 All rights reserved 3BS ISO 13756:2015ISO 13756:2015(E)The silver content of the sample WAgin parts by mass per thousand () is calculated using Formula (3):WmmAg=Agss103(3)wher
45、emsis the mass of the sample, in milligrams.8.2 RepeatabilityThe results of duplicate determinations shall correspond to better than one part per thousand () by mass of silver. If the variation is greater than this, the assay shall be repeated.9 Test reportThe test report shall include the following
46、 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, i.e. ISO 13756:2014;d) silver content of the sample, in parts by mass per thousand (), as single values and mean values
47、;e) if relevant, any deviations from the method specified in this International Standard, i.e. ISO 13756:2014;f) any unusual features observed during the determination;g) date of test;h) identification of laboratory carrying out this analysis;i) signature of laboratory manager and operator.4 ISO 201
48、5 All rights reservedBS ISO 13756:2015ISO 13756:2015(E)Bibliography1 ISO 9202, Jewellery Fineness of precious metal alloys2 ISO 11427, Jewellery Determination of silver in silver jewellery alloys Volumetric (potentiometric) method using potassium bromide ISO 2015 All rights reserved 5BS ISO 13756:20
49、15ISO 13756:2015(E) ISO 2015 All rights reservedICS 39.060Price based on 5 pagesThis page deliberately left blankBSI is the national body responsible for preparing British Standards and other standards-related publications, information and services.BSI is incorporated by Royal Charter. British Standards and other standardization products are published by BSI Standards Limited.British Standards Institution (BSI)BSI Group Headquarters389 Chiswick High Road London W4 4AL UKAbout usWe bring together busin
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