Lightweight 8A Fire Assaying Legend Crucibles Rapid Absorption

                    8A Fire Assaying Magnesia Cupels

     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.

Features:

1. Made of Magnesite

2. Used for smelting and assaying

3. High thermal shock resistance

4. Magnesia: ≥95%

5. Silica, Silicon dioxide: 0-5%

6. Property: high refractoriness(1100 centigrade degrees),rapid absorption(70%),and recovery rate of 97%-98.5%,easy to use, without milling.

      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

with bone-ash cupels.