AS 5006.2 pdf download

AS 5006.2 pdf download.Silver and silver bearing alloys
1  Scope
This Standard sets out gravimetric procedures for the determination of silver content in the range 1 % to 99 % in silver and silver bearing alloys with < 2 % nickel, < 0.05 % rhodium, < 0.05 % tungsten, < 1 % platinum and < 3 % palladium. NOTE 1  If gold, platinum or palladium are present they are retained with the silver. Consequently they need to be quantified and the silver content appropriately adjusted. The gold content can be quantified using AS 3515.1 or AS 3515.2 as appropriate and the platinum and palladium quantified using AS 4119. NOTE 2  Recommended methods of sampling bullion for use with this Standard are provided in Appendix A. NOTE 3  The presence of the following elements may cause difficulties in obtaining a homogeneous sample: iron, lead, antimony, nickel or arsenic.
3  Definitions
For the purpose of this Standard, the definitions below apply. 3.1 cupellation the process by which the precious metals are separated from the lead and other base metals with which they are alloyed. It is also the process whereby the sample, having been wrapped in lead sheet/foil with the necessary additives (i.e. silver or copper or both), is homogenized in the molten state prior to the separation of the gold and silver 3.2 laboratory sample a sample as prepared for sending to the laboratory and intended for inspection or testing 3.3 may indicates the existence of an option 3.4 prill the “button” or “bead” of precious metal obtained from the cupellation process 3.5 proof a reference sample included in every batch of assays in order to monitor the effect of assay conditions 3.6 reference standard a reference material included in each batch of samples to determine the accuracy of the analysis 3.7 shall indicates that a statement is mandatory 3.8 should indicates a recommendation 3.9 test portion the portion of material taken from the test sample or, if both are the same, from the laboratory sample, on which the test or assay is actually carried out 3.10 test sample a sample prepared from the laboratory sample, and from which test portions will be taken 3.11 total precious metals (TPM) the sum of gold, silver, platinum and palladium remaining after the cupellation process
4  Principle
An accurately weighed test portion is cupelled, cleaned and weighed. The total precious metal content is calculated and if present, the gold, platinum and palladium content is subtracted and the silver content determined.
5  Reagents
Analytical grade reagents (AR) shall be used. Deionized or glass distilled water of Grade 3 as defined in ISO 3696 shall be used. Reagents shall be as follows: (a) Proof gold. Gold containing at least 99.9965 % Au with a previously determined accurate value. (b) Proof silver. Silver containing at least 99.99 % Ag and less than 5 mg of gold per kilogram of silver. (c) Copper metal – AR grade. (d) Lead foil. Assay grade lead foil.
6  Apparatus
The apparatus shall be as follows: (a) Magnesite cupels. The choice of cupel size is governed by the ability of the cupel to absorb lead, and the expected amount of base metal in the test sample. The most commonly used cupel weighs approximately 36 g, and is suitable for up to 7 g of lead. A 54 g cupel is used for test samples containing a high base metal content, and is suitable for up to 14 g of lead. NOTE  Magnesite cupel blocks of similar lead absorption capacity are also suitable. (b) Anvil and hammer. Of polished steel. (c) Analytical balance. Capable of a resolution of 0.01 mg. (d) Cupellation furnace. Capable of attaining a temperature of 1100 °C ± 50 °C, and maintaining a controlled oxidizing atmosphere. NOTE  A standard muffle furnace is not a satisfactory apparatus. (e) Prill cleaning brush. Having tufts of stiff bristle or nylon. NOTE  Metal tufts are not satisfactory for this purpose.