Formerly the plan adopted in the separation of this metal was cupellation alone.
This plan of cupellation which we have just described is still adopted in many continental works in the assaying of silver-lead ores.
The cupellation temperature for gold~ is an orange-red heat or perhaps a little hotter.
Care must be taken to remove the cupels as soon as cupellation has finished.
For the cupellationof 1 gram of a silver copper alloy containing different percentages of copper, the following quantities of lead should be used:-- Percentage of Copper in Alloy.
As with silver so with gold the predominant cause of the cupellation loss is the solution of the metal in the molten litharge which passes into the cupel.
The loss in cupellationhaving been allowed for by any of the usual methods (see p.
It is easy to determine what allowance must be made for the loss in cupellationby cupelling side by side with the assay piece an alloy of similar and known composition.
But the cupellation loss is smaller with less gold and greater with more copper, and it so happens in these assays that these two opposites nearly neutralise one another.
There can, thus, be little doubt that the cause of the greater part of the "cupellation loss" is a chemical one and cannot be counteracted by a mechanical contrivance.
The proportion of lead required~ for the cupellation of any particular alloy requires consideration.
In large works the silver-lead alloy is removed when it contains 60-80% silver, and the cupellation of the rich bullion from several concentration furnaces is finished in a second furnace.
Thus, while cupellation still furnishes the only means for the final separation of lead and silver, it has become an auxiliary process to the two methods of concentration given.
This material can be a partial product from almost any cupellation where oxidation takes place below the melting point of the oxide.
The alloy which settles at the bottom of the other substances in the pot is carried to the cupellation furnace, and the slags are re-melted with the other silver slags.
The probable explanation of this conflict arises in the resemblance of cupellation furnace bottoms to lead carbonates, and the native molybdaena of Dioscorides; and some of those referred to by Pliny may be this sort of lead ores.
This furnace, vaulted with unbaked bricks, is similar to an oven, and also to the cupellation furnace, in which the lead is separated from silver, which I described in the last book.
This alloy we call "rich" silver-lead; it is carried to the cupellation furnace, in which lead is separated from silver.
Further, if we are to conclude its necessary association with silver, we must assume a knowledge of cupellation for the parting of the two metals.
These pieces of metal are afterward heated in iron basins and smelted in the cupellation furnace by the smelters.
The third part is nine feet wide and contains two separate rooms of equal size, in one of which is the assay furnace, while the other contains the metal to be melted in the cupellation furnaces.
The coppery skimmings from the cupellation furnace are referred to again in Note 28, p.
The history of cupellation is specially dealt with in note on p.
In assaying lead ores very poor in silver the best quantity to be taken for cupellation is 500 gr.
In the Royal Mint, the cores of ox-horn are selected for this purpose; and the ashes produced are about four times the expense of the bone-ash, used in the process of cupellation upon the large scale.
These figures exhibit the cupellation furnace of the principal smelting work in the Hartz, where the following parts must be distinguished; (fig.
When the copper is alloyed with very small quantities of gold, cupellation would afford very uncertain results; we must then have recourse to liquid analysis.
He may effect this purpose either by fusing the coarser alloys with nitre in a crucible, or by adding finer alloy, or even fine silver, or finally, by subjecting the coarser alloys to a previous cupellation with lead on the great scale.
But, independently of the objection from its high price, bismuth has the disadvantage of boiling up, as well as of rocking or vegetating, with the silver, when the cupellation requires a high heat.
The phenomena of the cupellation of gold are the same as of silver, only the operation is less delicate, for no gold is lost by evaporation or penetration into the bone-ash, and therefore it bears safely the highest heat of the assay furnace.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "cupellation" in a variety of sentences. We hope that you will now be able to make sentences using this word.
