When a batch of articles is received by Singapore Assay Office, the whole packet will be weighed and checked to ensure that all the information is correct. Then, a sample will be taken from the packet for assaying.
This ancient technique is first referenced by the Egyptians in a Cuneiform tablet dating back to around 1360 BC. It remains the most accurate technique for gold assay and serves as the standard technique against which all others are compared.
The principle is based on the removal of all base metals from a small weighed sample by oxidation in the cupellation stage to leave a pure gold-silver alloy, followed by removal of the silver by dissolution in nitric acid (the parting stage) to leave a residue of pure gold which is then weighed to allow calculation of the gold content.