BOOK X. 447 



into cakes. The glass extracted from the crucible is ground to powder, and 

 to this arc added litharge, argol, glass-galls, and saltpt^tre, and they are 

 melted in an earthen crucible. The button that settles is transferred to the 

 cupel and rc-melted. 



If the silver was not sufficiently dried by the heat of the fire, that which 

 is contained in the upper jjart of the ampulla will appear black ; this when 

 melted will be consumed. When the lute, which was smeared round the 

 lower part of the ampulla, has been removed, it is placed in the crucible and 

 is re-melted, until at last there is no more appearance of black^^. 



If to the first aqua the other which contains silver is to be added, it 

 must be poured in before the powerful vapours appear, and the aqua gives off 

 the oily substance, and the operculum becomes red ; for he who pours in the 

 aqua after the vapour appears causes a loss, because the aqua generally spurts 

 out and the glass breaks. If the ampulla breaks when the gold is being parted 

 from the silver or the silver from the aqua, the aqua will be absorbed by the 

 sand or the lute or the bricks, whereupon, without any delay, the red hot coals 

 should be taken out of the furnace and the fire extinguished. The sand and 

 bricks after being crushed should be thrown into a copper vessel, warm water 

 should be poured over them, and they should be put aside for the space of 

 twelve hours ; afterward the water should be strained through a canvas, and 

 the canvas, since it contains silver, should be dried by the heat of the sun or 

 the fire, and then placed in an earthen crucible and heated until the silver 

 melts, this being poured out into an iron mould. The strained water should 

 be poured into an ampulla and separated from the silver, of which it contains 

 a minute portion ; the sand should be mixed with litharge, glass-galls, 

 argol, saltpetre, and salt, and heated in an earthen crucible. The button 

 which settles at the bottom should be transferred to a cupel, and should 

 be re-melted, in order that the lead may be separated from the silver. The 

 lute, with lead added, should be heated in an earthen crucible, then 

 re-melted in a cupel. 



We also separate silver from gold by the same method when we assay 

 them. For this purpose the alloy is first rubbed against a touchstone, in 

 order to learn what proportion of silver there is in it ; then as much silver 

 as is necessary is added to the argentiferous gold, in a bes of which there 

 must be less than a semi-uncia or a semi-uncia and a sicilicus^^ of copper. 

 After lead has been added, it is melted in a cupel until the lead and the 

 copper have exhaled, then the aUoy of gold with silver is flattened out, and 

 little tubes are made of the leaves ; these are put into a glass ampulla, 

 and strong aqua is poured over them two or three times. The tubes after 

 this are absolutely pure, with the exception of only a quarter of a siliqua, 

 which is silver ; for only this much silver remains in eight unciae of gold^^. 



'^We do not understand this " appearance of black." If the nitrate came into contact 

 with organic matter it would, of course, turn black by reduction of the silver, and sunlight 

 would have the same effect. 



^*This would be equal to from 62 to 94 parts of copper in 1,000. 



^^As 144 siltquae are i uncia, then J siliqua in 8 unciae would equal one part silver in 

 4,608 parts gold, or about 999.8 fine. 



