High Hardness 9A Magnesia Cupels
Fire assay it is a classical analytical method for applying metallurgical principles and techniques to analytical chemistry. To test the content of precious metals in minerals and metal products determined by melting and roasting.
Top Diameter:51mm or 56mm
Bottom Diameter:39mm or 46mm
Height:34mm or 38mm
Height of Ridge:13mm or 15mm
Insied Diameter:40mm or 46mm
Depth of cup:13mm or 15mm
Cupels. — A cupel is a porous cylinder or inverted-cone frustum of refractory material with a cupped depression in the upper end for retaining the lead button. In modern practice, cupels are made of bone ash, cement, bone-ash-cement mixtures, or magnesia. Magnesia cupels are purchased as a finished product, but the others are usually made at the assay office.
Bone-ash cupels absorb a weight of litharge about equal to their own, cement cupels absorb slightly less than their weight, and magnesia cupels absorb three-fourths of their weight. Magnesia cupels are denser than bone-ash or cement cupels, hence a magnesia cupel of a given volume absorbs as much litharge as a bone-ash cupel of the same volume.
Magnesia cupels have a higher heat capacity and thermal conductivity than bone-ash or cement cupels, and hence the heat of oxidation of the dwelling lead is abstracted more rapidly. The alloy is therefore maintained at a lower temperature than with bone-ash or cement cupels, but higher muffle temperatures must be maintained throughout the cupellation cycle. Largely on account of lower alloy temperature near the finish of cupellation the loss of silver by cupel absorption is greatly decreased and is usually less than half of the loss obtained with bone-ash cupels, under analogous cupellation conditions. The gold loss with magnesia cupels is the same as