[ 150 I [Book VI, 



H A P. XXVII. 



ZINC. 



ejrriptien of this- Metal Pbilafopber's WoolUnion 

 Acids. White Vitriol. Detonation of Zinc nvith Nitre. Combi- 

 nation with Metals. Pewter. Its Ufe in Fire-works. Natural-^ 

 Hijtory of Zinc.Catawine, Black Jack. Brafs, honu made. 

 . Pinchbeck. 



THIS metal is in fome degree malleable, and 

 therefore holds a middle place between the 

 ferni-metals and metals, though it is ufuaily referred 

 to the former divifion. Its appearance is blue and 

 brilliant, and when- broken it is found to be cryftal- 

 lizcd in narrow plates. It melts when red hot; if 

 heated in clofe vefiels to a vivid red or white heat^ 

 the whole of it rifes in vapour, and may again be 

 condenfed without any change. When heated, how- 

 ever, in contact with air, it burns rapidly with a white 

 flame and crackling noife, and is converted into a 

 white, fofr, and flocculent fubftance, railed fbwrrs of 

 zinc, or lana philofophcrum. If the zinc is burnt in 

 a deep crucible, this calx attaches itfelf to the upper 

 part of it, though fome part is always loft even in the 

 deeped yeffel, which will admit the air with fufHcient 

 freedom to maintain the combuftion. If a gentle heat 

 is applied no light is produced, and the furface of the 

 zinc becomes gradually covered by a grey calx, which, 

 changes to white, by being afterwards heated in con- 

 tact with air. Zinc 5s lo apt to undergo this change 

 that it is difficult to melt fmall pieces of it into a rnafs, 

 for in the moment after they arrive at the melting 



