ASSAYS LABORATORY EQUIPMENT FOR PRECIOUS METALS.
FIOA INTERNATIONAL is very specialized in projecting, manufactoring and sale of assay laboratory equipment for precious metals, used for the determination of gold in jewellery alloys by means of cupellation method (fire assay).
The International Standard, specifies that the cupellation method (fire assay ISO 11426) is the only one legally recognized for the determination of gold in gold jewellery alloys.
The procedure is applicable specifically to gold alloys incorporating silver, copper and zinc.
Some modifications are indicated where nickel and/or palladium are present.
ISO 11426 is intended to be used as the recommended method for the determination of fineness in alloys covered by ISO 9202.
FIOA INTERNATIONAL has developed a significant know-how which can make much easier the life for the assayer. As a general preview, we can say that the gold testing through fire assay by cupellation analysis, requires small samples of gold to be carefully weighed in a vary precise electronic scales, and after, wrapped in lead foil together with a specific previously-known quantity of silver.
The samples are placed on particular magnesite “cupels” that can absorbe any non-precious metals,lead etc. etc. This absorption happened when the cupels with the sample are placed into a special cupellation furnace firing a specific temperature .
This process leaves the sample bottons of pure gold and silver which are boiled in nitric acid with a particular concentration in order to dissolve out the silver and then annealed to complete the process, leaving just fine gold.
A comparison of the weight of the pure gold with the weight of the original sample provides the degree of purity. Slightly different method may be used depending on the concentration of gold.