EN 31426:1994
(Main)Determination of gold in gold jewellery alloys - Cupellation method (fire assay) (ISO 11426:1993)
Determination of gold in gold jewellery alloys - Cupellation method (fire assay) (ISO 11426:1993)
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Bestimmung von Gold in Gold-Schmucklegierungen - Dokimatisches Verfahren (Kupellationsverfahren) (ISO 11426:1993)
Diese Norm beschreibt ein dokimastisches Verfahren (Kupellationsmethode) für die Bestimmung von Gold in Gold-Schmucklegierungen. Der Goldgehalt der Legierungen liegt vorzugsweise zwischen 333 und 930%. Das Verfahren gilt insbesondere für Goldlegierungen, die Silber, Kupfer oder Zink enthalten. Für nickel- und/oder palladiumhaltiges Weissgold werden Verfahrensabänderungen angegeben. 6
Dosage de l'or dans les alliages d'or pour la bijouterie-joaillerie - Méthode de coupellation (essai au feu) (ISO 11426: 1993)
Določevanje zlata v zlitinah za zlati nakit - Kupelacijska metoda (talilna analiza) (ISO 11426:1993)
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Bestimmung von Gold in Gold-Schmucklegierungen - Dokimatisches Verfahren (Kupellationsverfahren) (ISO 11426:1993)Dosage de l'or dans les alliages d'or pour la bijouterie-joaillerie - Méthode de coupellation (essai au feu) (ISO 11426: 1993)Determination of gold in gold jewellery alloys - Cupellation method (fire assay) (ISO 11426:1993)39.060NakitJewelleryICS:Ta slovenski standard je istoveten z:EN 31426:1994SIST EN 31426:1998en01-april-1998SIST EN 31426:1998SLOVENSKI
STANDARD
SIST EN 31426:1998
SIST EN 31426:1998
SIST EN 31426:1998
SIST EN 31426:1998
SIST EN 31426:1998
I N T E R NAT I O NA L STANDARD IS0 11426 First edition 1993-05-01 Determination of gold in gold jewellery alloys - Cupellation method (fire assay) Dosage de l'or dans les alliages d'or pour la bijouterie-joaillerie - Méthode de coupellation (essai au feu) -- Reference number IS0 11426:1993(E) SIST EN 31426:1998
IS0 11426:1993(E) Foreword IS0 (the International Organization for Standardization) is a worldwide federation 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. 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 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. International Standard IS0 1 1426 was prepared by Technical Committee ISO/TC 174, Jewellery. 0 IS0 1993 All rights reserved. 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-1 21 1 Genève 20 Switzerland Printed in Switzerland SIST EN 31426:1998
INTERNATIONAL STANDARD IS0 11426:1993(E) Determination of gold in gold jewellery alloys - Cupellation method (fire assay) 1 Scope This International Standard specifies a cupellation method (fire assay) for the determination of gold in gold jewellery alloys. Preferably the gold content of the alloys lies between 333 and 930 parts by mass per thousand of gold. The procedure applies specifically to gold alloys incorporating silver, copper and zinc. Some modifications are indicated where nickel and/or palladium are present in the so-called white gold alloys. 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 % (dm), p20 = 1,2 g/cm3, free of halide. 4.2 Nitric acid, 49 % (dm), p20 = 1,3 g/cm3, free of halide. 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. 4.3 bismuth, as foil, beads or tablets. gradet free Of precious metals and 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this International Standard. 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 IEC and IS0 maintain registers of currently valid International Standards. IS0 9202:1991, Jewellery - Fineness of precious metal alloys. 3 Principle The gold alloys are inquarted with silver, compounded with lead and cupelled in a cupellation furnace until a precious metal button is obtained. After flattening and rolling, the silver is extracted (parted) in nitric acid and the gold is weighed. Possible systematic errors in the procedure are eliminated by assaying standard proof samples in parallel. White gold alloys containing palladium and/or nickel require some procedural changes. 4.4 Silver, for inquartation, minimum purity 999,9 parts by mass per thousand (%d, free of gold and platinum group metals. 4.5 Pure gold, for proof samples, minimum purity 999,9 parts by mass per thousand (%O). 4.6 Palladium, for proof samples, minimum purity 999,9 parts by mass per thousand free of gold and other platinum group metals. 4.7 Nickel, for proof samples, minimum purity 999 parts by mass per thousand (%O), free of gold and platinum group metals. 4.8 Copper, foil or wire, minimum purity 999 parts by mass per thousand free of gold and platinum group metals. 4.9 Borax, (Na2B,0,), anyhdrous. 5 Apparatus Ordinary laboratory apparatus and 5.1 Cupellation furnace, in which an oxidizing at- mosphere can be maintained. N.B. A standard muffle furnace is not satisfactory for this purpose. 1 SIST EN 31426:1998
IS0 11426:1993(E) 5.2 Magnesium oxide cupels, usually of diameter 22 mm to absorb 6 g of lead, usually of diameter 26 mm to absorb 10 g of lead, or blocks of cupels of similar absorption. 5.3 Parting flasks, or platinum basket. 5.4 Parting cups, unglazed porcelain crucibles. 5.5 Cupellation tongs. 5.6 Assay pliers. 5.7 Polished anvil, may be replaced by a press, polished and reserved for this purpose. 5.8 Polished hammer, of minimum mass 400 g, may be replaced by a press, polished and reserved for this purpose. 5.9 Scorification dishes, usually of diameter 50 mm. 5.10 Jewellers' rolls. 5.1 1 Platinum-tipped crucible tongs. 5.12 Assay cleaning brush, of stiff bristle or nylon but brass. 6 Sampling The sampling procedure for gold jewellery alloys shall be agreed upon until a corresponding standard method has been published. For coated articles, appropriate precautions that have been agreed upon shall be taken, to exclude the coating from the determination. 7 Procedure 7.1 Yellow gold alloys 7.1.1 Analysis samples Transfer at least two samples of the alloy, preferably between 125 mg and 250 mg weighed accurately to the nearest 0,Ol mg, into assay grade lead foil (4.3). The mass of foil (or foil plus beads) should be at least 4 g for yellow gold samples up to 200 mg, and 6 g for samples from 201 mg to 300 mg (250 mg). Add pure silver (4.41, equivalent to 2,3 to 3 times the mass of fine gold present. Roll and compress the lead foil into a tight ball. 7.1.2 Proof assay samples Weigh, as described in 7.1 .l, at least two proof assay samples of proof gold (4.5) and pure silver (4.4) in masses which correspond to the expected gold and silver contents (including the inquartation addition) of the assay sample. The total content of base metals in the assay samples is taken into consideration by the addition of a corresponding quantity of copper. Treat the proof assay samples and the assay samples in 7.1.3 and 7.1.4 in the same manner. 7.1.3 Cupellation and treatment of precious metal but
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