240 



BOOK VII. 



If the whole space of the furnace covered by the muffle is not filled with 

 scorifiers, cupels are put in the empty space, in order that they may become 

 warmed in the meantime. Sometimes, however, it is filled with scorifiers, 

 when we are assaying many different ores, or many portions of one ore at the 

 same time. Although the cupels are usually dried in one hour, yet smaller 

 ones are done more quickly, and the larger ones more slowly. Unless the 

 cupels are heated before the metal mixed with lead is placed in them, they 



A — Claws of the tongs. B — Iron, giving form of an egg. C — Opening. 



frequently break, and the lead always sputters and sometimes leaps out of them ; 

 if the cupel is broken or the lead leaps out of it, it is necessary to assay 

 another portion of ore ; but if the lead only sputters, then the cupels should 

 be covered with broad thin pieces of glowing charcoal, and when the lead 

 strikes these, it falls back again, and thus the mixture is slowly exhaled. 

 Further, if in the cupellation the lead which is in the mixture is not con- 

 sumed, but remains fixed and set, and is covered by a kind of skin, this is a 

 sign that it has not been heated by a sufficiently hot fire ; put into the 

 mixture, therefore, a dry pine stick, or a twig of a similar tree, and hold it 

 in the hand in order that it can be drawn away when it has been heated. 

 Then take care that the heat is sufficient and equal ; if the heat has not 

 passed all round the chcirge, as it should when everything is done rightly, 

 but causes it to have a lengthened shape, so that it appears to have a tail, 

 this is a sign that the heat is deficient where the tail lies. Then in order 

 that the cupel may be equally heated by the fire, turn it around with a smaU 

 iron hook, whose handle is Ukewise made of iron and is a foot and a half long. 



Small iron hook. 



Next, if the mixture has not enough lead, add as much of it as is required 

 with the iron tongs, or with the brass ladle to which is fastened a very long 

 handle. In order that the charge may not be cooled, warm the lead beforehand. 



