The cupel is made of the ashes of burnt bone, and it is better to make them on the spot, as the bone ash may be carried anywhere without damage, whereas the cupels are very fragile.
The cupels are tightly consolidated by pressure in an iron mould of the form shown in Fig.
After the metal has been melted in these cupels it is run out into moulds, which shape the metal into plates about twenty inches long and ten in width.
Inside of these furnaces are shallow cupels over which a current of air passes.
These small cupels are best made by grinding the unsaturated portion of a used cupel to a fine powder, and compressing the dry powder into a small Berlin crucible or scorifier; the face should be made quite smooth by pressure from a pestle.
Prepare six cupels and charge them in the annexed order (fig.
Cupels do not bear transport well; hence the assayer generally has to make them, or to supervise their making.
These cupels are square blocks, a little less than 2 inches across, and a little more than three quarters of an inch deep.
The cupelsare put in a warm place to dry for two or three days.
If these larger cupels are not at hand the larger buttons will have to be reduced in size by a scorification before cupelling.
There should be no unnecessary handling of the cupels once they have been placed in the muffle.
After the muffle has cooled down for the withdrawal of the last batch, and the old cupels have been taken out, the new cupels for the next batch should be put in their place.
Cupels made with wet bone-ash should be slowly dried; and if in the muffle they can be slowly brought to an orange-red heat it is all the better.
With four assay pieces, the cupelsshould be placed close together in two rows of three across the muffle; the two check pieces are put in the middle cupels.
The furnace should then be stoked and made ready for the next cupellations; by the time the furnace is ready the cupels will be ready also.
In ten cupellations with the same quantities of gold and lead, but at an ordinary temperature, the gold recovered from the cupels varied from 1.
One plan is to allow the cupels to cool in the muffle itself, the mouth being closed with hot charcoal.
A little Phlogiston also may still be left in the ashes of which the cupels are made; and that is another reason for calcining them before they are used.
Both moulds are made out of brass and have no bottom, in order that the cupels can be taken out of them whole.
The cupels are made of ashes; like the preceding scorifiers they are tray-shaped, and their lower part is very thick but their capacity is less.
In the smaller ones are made the cupels in which silver or gold is purged from the lead which has absorbed it; in the larger ones are made cupels in which silver is separated from copper and lead.
Some make them out of all kinds of ordinary ashes; these are not good, because ashes of this kind contain a certain amount of fat, whereby such cupels are easily broken when they are hot.
The moulds in which the cupels are moulded are of two kinds, that is, a smaller size and a larger size.
Although the cupels are usually dried in one hour, yet smaller ones are done more quickly, and the larger ones more slowly.
Assayers of our own day, however, generally make the cupels from beech ashes.
Wrap each sample separately in paper, and afterwards place two small pieces of lead in two cupels which have first been heated.
To enable cupels of the best quality to be made, all the impurities must be removed from the ashes.
In the works in which silver is separated from copper, they make cupels from two parts of the ashes of the crucible of the cupellation furnace, for these ashes are very dry, and from one part of bone-ash.
These cupels are allowed to dry in the air for some time before they are used.
The cupelsare formed in a circular mould made of cast steel, very nicely turned, by which means they are easily freed from the mould when struck.
When the operation is performed, the cupels are placed in the furnace in situations corresponding to these assays on the board.
The cupels used in the assay process, are made of the ashes of burnt bones (phosphate of lime).
The same number of cupels are put into the muffle.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "cupels" in a variety of sentences. We hope that you will now be able to make sentences using this word.
