Z IN

' Z I N

( 505 ■)

decompofed into two portions, of which one isinfoluble and the other readily foluble in thisfluid. The former is fulphite of zinc alreadymentioned ; the latter is Sulphuretted fulphite ofzincj it gives out on the addition of fulphuricacid both fulphur and fulphurous acid, and tothis are obvioufly owing all thofe properties ofthe compound fait by which it is diftinguiffiedfrom the pure fulphite.

Nitric acid, moderately ftrong, is faid to becapable of inflaming zinc filings, and even whenmuch diluted a£ts on this metal with great vio-lence, and with a copious difengagement of ni-trous gas and nitrous oxyd. The folution is gene-rally of a pale greenifliyellow colour,and is highlycauftic: by evaporation and cooling it depofitsNitrat of zinc , in compreffed, ftriated, tetrahedralprifms, terminated by tetrahedral pyramids.The fpecific gravity of this fait is 2.09. Itabforbs moifture from the air, and deliquiates ;it is readily foluble both in water and alcohol.When laid on hot coals it melts and detonatesrather feebly, giving out a faint reddifh flame ;when heated perfe in an earthen crucible it isdecompofed, giving out nitrous and oxygengaffes, and the metal remains behind in theftate of yellowifh oxyd.

Muriatic acid a<lfts with much rapidity onzinc, hydrogen gas of very confiderable puritybeing given out. The folution is clear andcolourlefs : by evaporation and cooling it gela-tinizes, but cannot be made to cryftallize.When diftilled, there firft arifes a little flrengand fuming muriatic acid, and then the muriatof zinc itfelf paffes over in a half folid con-fluence, on which account it is often calledbutter of zinc. This fublimed muriat is of anopake white colour, and confifts of minuteprifmatic cryftals. It is fufible by a gentle heat,abforbs moifture from the air, and affumes agelatinous eonfiftence; it is not decompofableby mere water, and is very foluble both in thisfluid and in alcohol: the alkalies decompofe it,throwing down a beautifully white oxyd.

Oxymuriatic acid gas inflames filings of zincthat are thrown into it, and the refult is a mu-riat of zinc not differing from the preceding.

Liquid phofphoric acid attacks zinc with effer-vefcence, hydrogen gas being given out: thephofphat of zinc thus produced forms a white in-foluble powder. This fait may alfo be procuredby adding to the fulphat, nitrat, or muriat ofzinc, any of the neutral phofphats.

Water impregnated with carbonic acid a£isreadily on either metallic zinc or its oxyds.

The folution by expofure to the air becomescovered with an iridefcent pellicle of oxyd.The moll ready way however of obtaining it isby the decompofition of the fulphat, or almoftany of the other falts, by means of a carbonatedalkali •, a denfe white precipitate is thus formed,which, when well waffled and dried, is pureGarbonat of zinc. According to Bergman, 100parts of metallic zinc, when diffolved in an acid,and precipitated by carbonated foda, afford 193parts of carbonat; but Bergman’s precipitateswere dried only at 212°, and therefore probablyretain d a confiderable portion of water. Ac-cording to Prouft,™ io» parts of zinc afford byfolution in nitric acid and precipitation by car-bonated potafh, 180 parts of dried carbonat jin which refult the experiments of Dize and ofHecht, exadtly coincide: thefe 180 parts arereduced by calcination to 125 of mere oxyd,hence the component parts of this fait whenthoroughly dried, are

55 Zlnc

14 Oxygen

31 Carbonic acid

100

The fluoric and boracic acids a£f upon zinc,the former rapidly, the latter with difficulty,but the properties of thefe falts have not beenexamined.

If zinc filings are digefted in diftilled vinegar,they diffolve in this fluid with effervefcence,and the refult is acetat of zinc; according toDe Laffone, 12 ounces of vinegar take up only2 drams of zinc; if however radical vinegar oracetic acid be employed, the above quantity ofmetal will be taken up by \ of an ounce of acid.Flowers of zinc are alfo foluble with eafe inacetic acid, a confiderable degree of heat beingexcited during the procefs. The tafte of thisfait is bitter and metallic. It cryftallizes in thinand ffiining hexagonal and rhomboidal plates:when heated per fe in a retort a part fub-limes' with little alteration, except that it iswhiter than before. When laid on hot coals itburns with a blue flame. It is readily folublein water and is decompofable by the alkalies,by the mineral acids, and by all thofe that formwith zinc an infoluble fait.

In cotifequence of the medical application ofacetat of zinc, the following faffs may be ofufe to the practitioner. The fpecific gravity ofa faturated folution of acetat of zinc made bydigefting the cryftallized fait in diftilled vinegar,

3 «

An. de Chim. xxxv. p. 55.

VOL II.