AS 3515.1:2005 pdf – Gold and gold bearing alloys Part 1: Determination of gold content(less than 30%)—Gravimetric (fireassay) method

AS 3515.1:2005 pdf – Gold and gold bearing alloys Part 1: Determination of gold content(less than 30%)—Gravimetric (fireassay) method.
This Section specifies the preliminary determination undertaken to determine the total precious metal content in order to choose which of the two procedures set out in Sections 3 and 4 is applicable, see Clause 2,4.
2.2 SAMPLE INSPECTION ANI) PREPARATION
The sample shall be taken and inspected for the presence of discernible inhomogeneities. contaminants and. in the case of a sample prepared by the vacuum tube method, piping (hollow centre). If any of these defects are present, the sample shall he rejected. If not supplied in a form suitable for assay. the sample shall be flattened to render it suitable for cutting.
NOTE: The sample should be taken using one of the options listed in Appendix A.
2.3 PRELIMINARY DETERMINATION OF TIlE TOTAL PRECIOU S METALS, APPROXIMATE COLD. SILVER AND TOTAL BASE METALS CONTENT
2.3.1 Test portion preparation
If the total precious metals content, approximate gold content or total base metals content is unknown, a preliminary assay shall be carried out as follows:
(a) Fold one sheet of approximately 7 g of lead foil (1 .4.8) into a cone.
(b) Weigh a test portion of approximately 500 mg and record the mass (ns1) to 0.1 mg.
(c) Fold the lead cone tightly around the contents and carefully squeeze it into a compact for iii.
2.3.2 Cupellalion
The cupellat ion procedure shall he as follows:
(a) Preheat the cupellatioii furnace (1.5.4) to 1100°C ±50°C. If nickel is present, the cupellation temperature should be at least 1100°C.
(b) Place cupels (1.5.1) into the preheated cupellation furnace using one cupel for each test portion and allow the cupels to attain the furnace temperature.
NOTE: Cupels should be arranged so that test portions arc evenly distributed from left to right and from the back to the front of the furnace.
(c) To minimize the temperature loss in the cupellation furnace, quickly place the folded cones onto preheated cupels in order from left to right and from the back to the front.
(d) Maintain the samples at the appropriate temperature until cupellation is complete, (25 mm to 30 mm), ensuring that adequate airt1os is maintained through the furnace to promote oxidation.
(e) Remove (he cupels from the furnace, maintaining them in the original spatial order, and allos them to cool in a well ventilated area.
(f) As soon as the material has solidified, loosen each prill from its cupel. Check that the prills are smooth, hard and shiny. If any prills arc dull, flat or fragmented (this being due to a high base-metal content). the determination shall be repeated sith additional lead.