Chap. 13.] Alum. 73 



defcriptions of Pliny are flill more "difficult to be 

 underftood, as he had not feen the fubftance which 

 he defcribes, but merely tranfcribed from others. The 

 factitious fait which is now called alum, was firft. 

 difcovered in the eaftern countries, but when, where, 

 or by what means, is unknown. On account of its 

 iimilar aftringency, and its ufe in the arts of tanning 

 and dying, the new fait has retained the old name. 



Among the moil early works for the preparation 

 of alum, was that of Roccho, a city of Lycia, now 

 called EdefTa, hence the appellation Roch alum (now 

 commonly miftaken for rock alum). In the neigh- 

 bourhood of Conftantinople, and other parts near 

 Smyrna, were many alum-works. The Italians hired 

 and made ufe of thefe, but about the fifteenth century 

 introduced the art into their own country. 



Bartholomew Perdix, or Pernix, a merchant of 

 Genoa, who had often been at Roccho, difcovered the 

 matrix of alum in the ifland of Ifchia, about the year 

 1459, an d eftablifhed a manufactory there; at the 

 fame time John de Caftro made the fame difcovery 

 at Tolfa, by means of the iiex aquifolium, which he 

 had alfo obferved to grow in the adjacent mountains 

 of Turkeyj and his opinion was confirmed by the tafle 

 of the ftones. The attempts of the Genoefe at Viter- 

 jbium and Volaterre fucceeded extremely well ; info- 

 much that an edift of Pope Pius II. prohibited the ufe 

 pf oriental alum. 



Manufactories were eftablifned in Spain, Germany, 

 England, Sweden, &c. in the courie of the fixteenth 

 century. 



The proportion of the principles may be afcertained 

 in the following manner : the water is expelled by a 

 gentle heat; the remaining mafs grows opake, fwclls, 

 foams, and at length grows quiet, fpongy, and friable ; 



the 



