Chap. 34.] Luna Corned. 223 



flexibility, and foftnefs, it is called tune cornea, or ar- 

 gentum corneum, and from this feveral other compounds 

 of metals with the muriatic acid have been called cor- 

 nea. It may be cut into tranfparent veflels refembling, 

 glafs. 



Aqua regia, or the compound of nitrous and mo- 

 riatic acids, acts ftrongly on filver, but forms a preci- 

 pitation in proportion as it feparates it from the mafs. 

 This effect m.ay be readily underftocd from what has 

 already been obferved. The nitrous acid diftblves the 

 fiiver, and the muriatic feizes it, and forms kina cornea* 

 which is infoluble. This procefs may be ufed to fepa- 

 rate gold from filver; the gold is held diffolved in the 

 aqua regia, but the filver is precipitated. 



After filver has been reduced to the calciform ftate 

 by folution in nitrous acid, and precipitation by alka- 

 lis, it is capable of folution in vinegar, and even in 

 lemon juice; but thefe compounds have not been ap- 

 plied to any ufe. 



To have filver perfectly pure we muft ufe quick- 

 filver, which, if poured into a folution of filver, is 

 attracted by the acid, and precipitates an amalgam with 

 the filver at the bottom of the yeflel. The quick- 

 filver is eafily feparated from the filver by heat alone. 

 A curious phenomenon arifes from this amalgam j a 

 kind of cryftallization takes place, which is formed by 

 the union of the filver with the running mercury. The 

 amalgam puts forth (hoots, which afterwards put forth 

 others, like the branches of a tree. The cryftalliza- 

 tion varies according to the conduct of the pfocefs, 

 and does not always anfwer, particularly if the mix- 

 ture is fhaken. It is called arbor Dian<?> or Diana's 

 tree*. The method of making it moft beautiful 



Diana's tree, from the whim of the alchemifts already noticed, 

 who appropriated iilver to the Moon or Diana, as ftated in a pre- 

 ceding note. 



is 



