tiS A SYSTEMOF 



SECT. CCXXXL 



Observations on Zink. 



It does not feem juft to conclude from old coins 

 and other antiquities, that it is evidently proved 

 that the making of brafs was known in the moft 

 antient times, and that it was their Ms Corinthia- 



rteratifed with fulphur. The fulphur, neverthelefs, exifts in 

 the d'fferent kinds of blende, equally as in the zink ore ; and 

 fhi» remarkable difference in their appearance muft be account- 

 ed for from another principle than the quantity of the zink 

 which they contain ; becaufe the yellow and white blendes are 

 ©ften found richer than the zink ores, but the zink ores are how- 

 ever more eafy to melt, and confequently more profitable. Per- 

 Bapa it is becaufe the blende does not contain a fufficient quan- 

 tity ef the phlogifton of the fulphur, to prevent the calcina- 

 tion of the zink. 



it is no matter whether a calcined blende is called calamine 

 or not, provided it has fuch properties that it may be employ- 

 ed to the fame purpofes. and with the fame advantage as that 

 calamine which nature has freed from its fulphur by its wea- 

 thering or decaying. This may be done with fome kinds of 

 Blende, and Mr Von Swab has given evident and excellent 

 proofs of it in Sweden ; infomuch that it would demonftratc 

 a: want of experience to infill that fulphur cannot be expelled 

 fey calcination, without destroying the zink itfelf, and that 

 flowers of zink may be produced from z nk ores in a calcining 

 Jteat, without addition of any phlogifton, 



Mr* Jufti however avers, that he has found an ore of this 

 quality, which in his Mineralogy he calls Zitkfpct ; but there 

 rs great reafon to doubt if it really contains any zink, until it 

 %$ proved whether the author added any phlogifton during the 

 calcination, or reduced the zink out of it ; L ."aufe, although the 

 flowers or' zink may not always be perfectly well calcined, yet 

 there is no inftance of a natural zink ore being discovered, 

 which by iffelf yields thofe flowers during the calcination : And 

 it requires, be£des, a ft.ong heat to produce thefe flowers from 

 3 perfect calx or glafs of this femi-metal, either natural or ar- 

 tificial, though mixed with a phlogitton ; for it could not have 

 been a native zink, fince it refembled a fpar, and fuch a one 

 wv }&cty is not to be found in nature. 



cum 



