e H E M 
grey, much heat is produced, and a Black powder is pre¬ 
cipitated, which was long unknown, but is found to Con- 
flit of carbure of iron, or plumbago. A large quantity 
of hydrogen gas, holding a fmall quantity of charcoal in 
folution, is difengaged. It affords a white fulphat of 
zink by evaporation, rather more foluble in hot than in 
cold water, and of which a portion cryftallizes by cool¬ 
ing. Very regular cryltals of this fait, known in the arts 
by the name of white copperas, white vitriol, or Gqflar 
vitriol, are eafily obtained by expofing for fome days to 
the air a folution of the fait made in boiling water, and a 
little evaporated : tetrahedral prifms are then formed, ter¬ 
minated by pyramids of four fides. Monnet, however, 
affirms, that this fait cryftallizes with great difficulty, 
and requires much evaporation, and fudden cooling, to 
afford regular cryftals without confidence. The white 
oxyd of zink likewife diflolves ill the fulphuric acid, and 
affords fulphat of zink. 
This fait has a ftrong ftyptic tafte. According to Hel- 
lot, it lofes a part of its acid by the action of fire, and 
then appears to be converted into fulpliit of zink, whole 
properties are not well known. The fulphat of zink is 
very little altered by expofure to air, when it is very 
pure: in the courfe of time its oxyd becomes calcined 
ltill more by abforbing oxygen ; it afl'umes a yellow co¬ 
lour, and is no longer perfe&ly foluble in water. Sul- 
phat of zink is decompofable by alumine, barytes, mag- 
nefia, lime, and the three alkalis. The oxyd or zink pre¬ 
cipitated by thefe fubftances, may be re-diffolved in acids, 
and even in alkalis. Ammoniac becomes of a dirty brown 
colour after diflblving it. The fulphat of zink d.ecom- 
pofes nitre, and is itfelf decompoled by this neutral fait. 
By diftiiling this mixture, two kinds of nitrous acid, which 
do not mix, are obtained, together with the glacial ful¬ 
phuric acid j we fhall fpeak more fully on this fubjeft at 
the article of fulphat of iron, or martial vitriol. 
A fulphat of zink, prepared in the large way at Goflar, 
is met with in commerce under the name of white vitriol. 
It is made thus: blendes are roafted, a portion of the 
fulpluir burns, and furnifhes fulphuric acid, which dif- 
folves the oxyd of zink. The roafted ore is then waflied, 
and the lixivium being decanted, is expofed to evapora¬ 
tion, and affords cryftals. The fait being melted by a 
gentle heat, fo as to deprive it of its water of cryftalliza- 
tion, and then differed to cool, becomes condenfed into 
white, opake, and granulated, maffes, refembling fugar. 
The vitriol of Goflar , when difl’olved in boiling water, 
cryftallizes by cooling. Its cryftals are fomevvhat reddifli, 
a circumftance to be attributed to the impurities of the 
fait, which is fuppofed to contain a fmall quantity of 
lead and iron. To purify it, zink may be thrown into 
its folution. This metal precipitates the oxyds of iron 
and of lead, becaufe it has a ltronger affinity with the 
fulphuric acid; and the liquor being filtrated, is conse¬ 
quently found to contain pure fulphat of zink. There 
is ltill greater reafo.n to think, that the impurity of the 
vitriol of Goflar confifts in the oxyd of iron, from the 
circumftance of the zink met with in trade being mag- 
netical, doubtlefs becaufe it contains iron. Experiments 
concerning this metal ought therefore not to be made, 
but with zin|k prepared by reducing the precipitate of 
lulphat of zink purified in the manner here fhewn. 
"We muft, however, obferve, that zink is very often mag- 
netical only at that part of the piece which has been 
cut with fciflars, or iron wedges. 
Nitric acid diflolves zink with great facility, and is de- 
compoled by it. This acid will diflolve about one-fifth 
of its weight of zink: Put the zink into a matrafs as be¬ 
fore, and pour over it weak or diluted nitric acid. A 
confiderable heat is produced in this folution, as well as 
in that wherein the fulphuric acid is ufed. The lively 
tffervefcence which accompanies this combination, is oc- 
eafioned by the difengagement of a large quantity of ni¬ 
trous gas. This.experiment fhews that zink decompoles 
the nitric acid, and deprives it of a portion of its oxy- 
Vol. IV, No. 197. 
I S T R Y. 289 
gen. The nitric acid holds £ much larger quantity of 
oxyd of zink in folution than the fulphuric. The nitric 
folution of zink is of a greenifh yellow, and not perfe&ly 
clear when newly made, but it lofes this colour, and be¬ 
comes transparent, after Handing for fome time. It is 
very cauftic, pnd quickly corrodes the fxin, though made 
with an acid diluted with water. It fufniffies, by evapo¬ 
ration and cooling, cryftals in tetrahedral ftriated fiat 
prifms, terminated by pyramids of four fides, likewife 
ftriated. The nitrat of zink, being put on hot coals, firft 
melts and detonates as the portions become dry, and the 
detonation is attended with a fmall reddifli flame. The 
fame phenomenon does not appear when the fufion is 
performed in a crucible. It cannot be dried, even by the 
mildeft heat, without alteration ; vapours of nitrous gas 
in this cafe e.fcape, and it becomes of a brown red, and 
of the confiftence of a jelly. If it be differed to cool in 
this ftate, it preferves its foftnefs for fome time; but, If it 
be kept heated for a fufficient time, it dries entirely, and 
leaves a yellowiffi oxyd. Hellot obtained from the diftil- 
lation of nitrat of zink a very fuming nitrous acid, and 
obferved the red colour it afl’umes in melting. It may 
be conceived, that, heat difengaging the nitrous gas of 
this fait, it pa.ffes to the ftate of nitrat of zink. It like¬ 
wife affords a certain quantity of oxygenous gas or vital 
air. The nitrat of zink quickly attra£ls humidity, and 
lofes its regular form after fome days expofure to the air, 
nothing remaining but ftriated and pointed prifms, whole 
figure can fcarcely be determined. 
The muriatic acid afts on zink as ftrongly as the ni¬ 
tric. During the rapid effervefcence which accompanies 
this combination, much hydrogen gas is difengaged, 
which has the fame properties as that afforded by the 
fulphuric acid ; and this laft is known to be derived from 
water decompofed by zink. Black flocks are gradually 
depofited, which is nothing elfe but a combination of 
carbon, or charcoal and iron, or carbure of iron. The 
folution of zink by the muriatic acid is colourlefs, and 
does not afford cryftals by evaporation ; when heated, it 
becomes of a blackilh brown, emits acrid and penetrating 
vapours of muriatic acid, and becomes very thick. Ex¬ 
pofed to the air for eight days in this ftate, it affords no 
cryftals. By diftillation it gives out a fmall quantity of 
very fuming acid, and a folid and fufible inuriat of zink. 
There remains in the retort ufed for this diftillation, a 
blackilh vitriform and deliquefcent matter. 
The liquid carbonic acid in which zink or its oxyd 
are digefted in the cold, diflolves, at the end of twenty- 
four hours, a confiderable quantity of this metal, accord¬ 
ing to Bergman. This folution, when expofed to the 
air, becomes covered with a pellicle, which refiefls vari¬ 
ous colours, and is merely a carbonat of zink, according 
to that celebrated chemilt. The aftion of the other acids 
on zink are not known. 
All the folutions of zink in acids are precipitated by 
lime-Water, magnefia, the fixed alkalis, and ammoniac. 
Silex and alumine form no combination with zink; but 
its oxyd enters into vitreous compofitions, and gives the 
glals a red colour. There is no aftion with barytes, 
llrontian, magnefia, and lime. If liquid potaffi or caul- 
tic foda be boiled over this metal, its liirface will be 
darkened, and afl’ume a dirty yellow colour, holding in 
folution a certain portion of the oxyd of zink, which 
cannot be feparated by acids. Ammoniac heated does 
not aift fo well upon zink, certainly on account of its 
volatility; -but, digefted upon zink in the cold way, it 
diflolves a little ; in the three alkaline folutions of zink, 
a certain quantity of hydrogen gas is difengaged, arifing 
from .the decompofition of the water. 
Gold and zink melt eafily together. Equal parts of 
thefe metals form a hard brittle inafs, which receives an 
excellent poliffi. The zink may be-feparated from the 
gold by oxydation in the fire, or by folution in nitric 
acid. Zink unites eafily with platina, and forms with it 
a brittle hard bluifti-coloured mixture. It is very difficult 
4 E to 
