ZINC. 



n water, and may be fonned readily by double decom- 



pofition. r r 1 -n. 



Tartrate and Citrate of Zinc — Both thefe falls exitt 

 ufuaUy in the form of powders, and are but little foluble 

 in water. They may be procured, like the oxalate, by double 

 decompofition. 



The other falts of zinc are of very little importance or 

 intereft, and do not therefore merit to be enumerated here. 

 The falts of zinc may be diftinguifhed m general by their 

 forming colourlefs folutions in water, by their yielding 

 white precipitates with prufliate of potafh, fulphuretted hy- 

 drogen, and the alkalies, and by the charaaeriftic circum- 

 ftance that zinc is not precipitated in the metallic ftate by 

 any other metal. 



Ufes of Zinc and its Compounds. — Neither this metal nor 

 its compounds, if we except brafs, are much employed in the 

 arts nor in medicine. A chief ufe of zinc is in the formation 

 of galvanic apparatus, and in eleftrical experiments. ( See 

 Galvanism and Electricity. ) As it is not a poifonous 

 metal, it has been recommended inftead of tin and lead for 

 domeftic purpofes ; but the eafe with which it is oxydized 

 makes it very unfit for all forts of culinary apparatus. 



The ftrong affinity of zinc for oxygen renders it of 

 great ufe as a chemical agent for precipitating other metals 

 from a ftate of folution in the metallic ftate. The oxyd of 

 zinc is ufed in medicine, both internally as a tonic, and ex- 

 ternally mixed with hog's-lard as an ointment. The native 

 carbonate is alfo ufed in the fame manner as an external ap- 

 plication. See Unguentum Calamine, and Unguentum 

 Zinei. 



The fulphate and the acetate Tjre the only falts of zinc ufed 

 in medicine ; for the properties of which, fee above. 



Zinc, Ores of, in Mineralogy. The ores of zinc are ge- 

 nerally aflbciated with lead-ores, and exift abundantly in va- 

 rious parts of England ; particularly in veins in the moun- 

 tain lime-ftone of Derbyfhire, Durham, Cumberland, York- 

 fhire, Somerfetfhire, and North Wales. The ores of zinc 

 are either oxyds, carbonates, or fulphurets of zinc, and are 

 principally known as calamine or blende. There is an ore 

 of zinc hitherto found only in North America, called by 

 Dr. Bruce red zinc-ore ; it occurs in feveral of the iron- 

 mines in Suffex county, New Jerfey. 



Red Zinc Ore is of a blood-red or aurora-red colour : it 

 occurs mafiive and diffeminated. The frefti frafture is fhining, 

 but becomes dull after long expofure to the air, and is co- 

 vered with a pearly cruft ; the principal frafture prefents 

 a foliated ftrufture ; the croft frafture is conchoidal. It is 

 opaque or tranflucent on the edges ; it yields a brownifh-yel- 

 low or orange ftreak ; it is brittle. The fpecific gravity is 

 6.22. It is infufible without addition by the blow-pipe, but 

 melts into a tranfparent yellow bead with borax. When 

 pounded and mixed with potafh, and expofed to heat, it melts 

 into an emerald-green mafs, which, on folution in water, 

 yields the fame colour ; but on the addition of the mineral 

 acids is immediately changed to rofe-red. This ore is fo- 

 luble in the mineral acids. Its conftituent parts are. 



brafs of the very fineft quality, poffefllng a high degree jf 

 malleabiUty, and fuited for the moft delicate workmanfhip. 

 Red zinc-ore is charafterized and diftinguifhed from red 

 filver-ore and red lead -ore by its infufibiUty ; the latter melt- 

 ing into a blackifh flag before the blow-pipe. Red orpiment, 

 with which it might be confounded, is diftinguifhed from 

 red zinc-ore by its volatility, and the garlic fmell which it 

 yields. This ore of zinc has greater fpecific gravity thatt 

 red copper-ore, and its folution in acids is colourlefs ; but 

 thofe of red copper are green. Calamine is divided by fome 

 mineralogifls into four kinds, fparry calamine, compact 

 calamine, earthy calamine, and eleftric calamine. 



Sparry Calamine : Zinc Carbonate, Haiiy. — Its colours 

 are greyifh and yellowifh-white, and fometimes green and 

 reddifh-brown. It occurs maffive, botryoidal, cellular, 

 ftalaftitic, and cryftallized, in acute and obtufe rhomboids, 

 and in longifh quadrilateral tables : the cryftals are fmall. 

 The luftre of fparry calamine is between refinous and vitre- 

 ous. The ftrufture is imperfeftly lamellar, and fometimes 

 radiated. It is tranflucent, or more or lefs tranfparent ; it 

 yields eafily to the knife. The fpecific gravity is 4.3. It is 

 infufible before the blow-pipe, and lofes about 34 per cent. 

 by ignition. With muriatic acid it effervefces, and is dif- 

 folved. According to Smithfon, the conftituent parts of 

 this ore from Derbyfhire are, 



Zinc .... 



Oxygen .... 

 Oxyds of manganefe and iron 



76 

 16 



8 



100 



Bruce's American Mineralogical Journal, p. 69. 



According to Dr. Bruce, this ore pofTeffes advantages 

 in the mamifafture of brafs over thofe generally ufed ; for 

 without any previous preparation, it affords with copper 



From Somen 



Compael Calamine : Zinc Carbonate, Haiiy. — Its colours 

 are, greyifh, greenifh, or yellowifh, and often brown, from 

 an intermixture with iron. It occurs mafSve, botryoidal, 

 diffeminated, ftalaftitical, reniform, and raamillated : it has 

 a dull, feebly gliftening, refinous luftre. The frafture is 

 uneven and coarfe-grained, or fphntery, and fometimes evcQ 

 a flatty conchoidal. It fometimes occurs in concentric la- 

 mellar concretions : it is opaque. Its chemical charafters 

 and conftituent parts are the fame as of the fparry calamine, 

 thefe minerals being only varieties differing in form from 

 each other. 



Earthy Calamine : Zinc Carbonate, Haiiy. — It is of a 

 greyifh or yellowifli-white colour, fometimes fnow-white ; 

 externally it is frequently covered with a tint of yellowifh - 

 brown. It occurs mafQve, and coating other minerals ; it is 

 opaque, and has an earthy frafture ; it yields to the nail, 

 and adheres to the tongue. The fpecific gravity is 3.358. 

 According to Smithfon, the conftituent parts are, 



100. 



EleSric Calamine: Zinc Oxyde, Haiiy — Its prevailing 

 colours are, greyifh, blueifh, or yellowifh-white ; externally 

 it is fometimes brownifli or blackifh. It occurs cryftallized, 

 mamillated, botryoidal, ftalaflitical, and maffive. Thecryf 

 tals are fix-fided prifms, with dehedral fununits, or acute 



oftahe- 



