The precious metals assay by cupellation is the most ancient and most used method for the analysis of precious metals. This is the system that requires less expensive machines and nevertheless it gives more accurate results compared with more modern methods (spectrophotometry or X rays). It is a destructive method because it needs some sample to process.

The cupellation is the operation that dissolves the precious alloy with the help of fused lead in a magnesite crucible which has the property, in a oxidizing atmosphere, of absorbing all non precious metals, leaving a small ball of silver-gold unaffected.

The operation to be followed are:

• Collecting of two samples of about 0,25 grams each by drilling the precious item to be analyzed
• Exact weighing of two sample
• Quartation with silver
• Cupellation at 1100°C in a oxidizing atmosphere
• Flattening of the small gold-silver ball and rolling with subsequent annealing
• Separation with different concentration of nitric acid
• Rinsing and drying of the only-gold chip remaining
• Final weighing

Required Machinery

• Column drill
• Precision analytical scale (5 decimals)
• Anti-vibrant table for scale
• Cupellation Furnace
• Machine to squash, roll and anneal the cupel-ball
• Polypropylene hood with electrical stoves for separation
• Scrubber for acid fumes treating
• Annealing furnace (if you make many assays)

Training
Training course will last for three days. The technician will be trained on the usage of our machinery and the procedures involved in precious metals assaying. The normes object of the course are the EN ISO 11426 / 00 and EN 31427. Training courses be held in Arezzo (Italy).