BOOK X. 



453 



A FURNACE IN WHICH THE AIR is DRAWN IN THROUGH HOLES. B GOLDSMITH'S FORGE. 

 C EARTHEN CRUCIBLES. D IRON POTS. E BLOCK. 



in which the air is drawn in through holes ; or else they are placed in a gold- 

 smith's forge. 



Just as aqua valens poured over silver, from which the sulphur has 

 parted the gold, shows us whether all has been separated or whether 

 particles of gold remain in the silver ; so do certain ingredients, if placed in 

 the pot or crucible " alternately " with the gold, from which the silver has 

 been parted by stibium, and heated, show us whether all have been 

 separated or not. 



We use cements 18 when, without stibium, we part silver or copper or both 

 so ingeniously and admirably from gold. There are various cements. Some 



"As will be shown in the historical note, this process of separating gold and silver 

 is of great antiquity in all probability the only process known prior to the Middle Ages, and 

 in any event, the first one used. In general the process was performed by " cementing " 

 the disintegrated bullion with a paste and subjecting the mass to long-continued heat at a 

 temperature under the melting point of the bullion. The cement (compositio) is of two 

 different species ; in the first species saltpetre and vitriol and some aluminous or silicious 

 medium are the essential ingredients, and through them the silver is converted into nitrate 

 and absorbed by the mass ; in the second species, common salt and the same sort of medium 

 are the essentials, and in this case the silver is converted into a chloride. Agricola does not 

 distinguish between these two species, for, as shown by the text, his ingredients are badly 

 mixed. 



