CHEMISTRY. 
ox yd of mercury united to a fiViall portion of the fuiphu- 
ric acid. It is coafiderably fixed, according to the ob- 
lervatffons of Kunckel, Macquer, and Bucquet. In this 
operation- the fulphuric acid is decompofed by a double 
elec tire attraction ; the mercury, which is a combuitible 
fu bftan.ee, unites to the oxygen contained in.the acid, 
while the heat difen gages the fulphureons gas and the 
water. The metal mult therefore be in the ftate. of an 
oxyd, and mult confequ'ehtly have much more fixity than 
fluid mercury. 
A portion of this fulphuric mercurial mafs is foiuble 
in water. When a large quantity of water is poured 
upon it, it mixes with the mafs, and a white powder pre¬ 
cipitates, if the water be cold; but, if boiling water be ul'ed, 
the powder is of a beautiful brilliant yellow colour ; draw 
off the liquor, and fet it afide ; then pour over the yellow 
powder a frefli quantity of boiling water, which is to be 
decanted in the fame manner; and continue to wadi the 
powder till the water comes away quite infipid. This 
was anciently called turbith mineral, or yellow precipitate. 
We now call it yellontu mercurial oxyd. This oxyd has no 
tafte. Melted by the blow-pipe with pholphoric glafs, it 
acquires a green colour. When urged by a ftrong- fire 
in a retort, it gives out at firft a Little fulphureons acid, 
and is then reduced into running mercury, giving out a 
great quantity of vital air. In a flow fire it is converted 
into the red oxyd of mercury. The water which has 
been poured on the white fulphuric mercurial mafs, is 
loaded with a portion of the acid which was not decotn- 
pofed ; but, as oxyd of mercury is vety foiuble in that 
acid, a certain quantity is always, taken up, fo that the 
water, holds in folution a true fulphat of mercury. By 
evaporating the water,, this lalt is depofited in fmail 
needles, the"form of which has not been determined, be- 
c.rafe they are fcarcely confiftent, and quickly attradt hu¬ 
midity. When boiling water is thrown on the cryftals 
of fulphat of mercury, they become yellow, and in the 
ffate of a mercurial oxyd, becaufe the water feparatfis 
the acid, which adheres but weakly, and isaves the oxyd 
pure. The fame event happens when the water em¬ 
ployed for the nrit wafhing or the mercurial mafs is moftly 
evaporated, and the remainder is afterwards diluted by 
the addition of a large quantity of boiling water, Lnitead 
of bringing it to cryltals. A yellow powder is precipi¬ 
tated in the ftate of a true oxyd. If cold water be ufed, 
the precipitate is white; but it immediately affumes a 
yellow colour by the addition of boiling water. In this 
manner the folution of the oxyd of mercury may be ren¬ 
dered decompofable or not by water. For this purpofe 
it is fufiicient to evaporate it nearly to cryfiallization, or 
to charge the acid with all the mercurial oxyd it is ca- 
pable of difl'olving ; for then the union of thefetwo bo¬ 
dies is eaiily deftroyed by water. Iff a fmall quantity of 
acid be added, water is no longer capable of caufmg a 
precipitation. Fourcroy proved this iu the moft fatisfac- 
tory manner, by difl'olving well-walked turbith. mineral 
in weak fulphuric acid ; the folution is not l'aturated 
with mercurial oxyd, and is at the fame time not preci- 
pitable by water. But if the folution be charged with as 
much turbith mineral as it can diffolve by the affiltance 
of heat, which may be done by adding that fubftance till 
it is no longer taken up, then the folution being poured 
into cold water, affords a white precipitate; or if into 
hot water, a yellow powder. In this ffate, if a fmall 
quantity of fulphuric acid be added, it ceafes fo afford 
any precipitate. The white mercurial oxyd which the 
fulphat of mercury depofits when cold water is poured on 
it, is very foiuble, and.may be made to difappear, by add¬ 
ing fulphuric acid to the. mixture. 
Sulpbat of. mercury may be. decompofed by magne/ia 
and lime, a yellow precipitate being depofited; and fixed- 
alkalis leparate an oxyd of mercury nearly of the fame- 
colour. Ammoniac does not precipitate fulphat of mer¬ 
cury when it contains an excels off acid; it forms a triple 
fait,.:Oiz ammoruacQ-mercurial fulphadi. When the fulphat 
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of mercury is properly neutralized, and without -excels 
of acid, only a fmall portion of black oxyd is feparated 
by the ammoniac, which it renders reducible by the con¬ 
tact of light alone. It forms a triple fait with the greater 
part of the fulphat of.metcury. This fait is not fixed by 
fire ; it melts and fublimes; it is reduced by a ftrong heat. 
Mercury is attacked by the nitric acid both hot and 
cold ; but the differences of temperature make a great 
difference in the folution : when the operation is per¬ 
formed cold, the folution cannot be decompofed bv dif- 
tilled water; but, if done with heat, the decomposition 
takes place; becaufe that, with heat, the acid is over¬ 
charged with the oxyd. To procure the folution of mer¬ 
cury in the nitric acid, put into a matrafs of a proper 
fize, one part of mercury,-with one and a half of the 
acid; when the firiu effervefcence has ceaft-d, place the 
matrafs on a land-bath, in order to afi'nt the folution by 
heat; but, if the acid be good, the folution will take 
place without fire. A great quantity of nitrous gas is 
difengaged; and the mercury, reduced to an oxyd, re¬ 
mains in folution. Tips faline metallic fubftance is ex¬ 
ceedingly cauftic, and capable of corroding and deftroy'- 
ing our organs. When it falls on the (kin, it forms (pots 
of fo deep a purple, that theyr appear almoft black ; thei'e, 
fpots cannot be diflipated but by the reparation of the 
epidermis, which 1'caLes off. The folution is ufed a-s a 
powerful efcharotic in furgery, by the name of mercurial 
wafer. The folution of mercury in the nitric acid is 
capable of affording cryftals, by a cooling only, in fiat 
needles, very long and very (harp, ftriated all their length. 
This fait is very cauftic, and corrodes the (kin in the 
fame manner as the loiution ; it deronates on burning 
coals. When very dry, a ftrong whitifh flame efcapes, 
which foon ceafes. Expcfed to the air, it becomes yel¬ 
low', and is decompofed very (lowly. 
The nit rat of mercury melts when heated in a crucible, 
and emits very thick r ed vapours. In proportion as it 
lofes its water and nitrous .gas, it takes a deeper yellow 
colour, which is afterwards converted to an orange, and 
laftly to a brilliant red. In this ftate it is called red pre¬ 
cipitate. We term it red oxyd of mercury by the nitric acid. 
Inftead of ufing the nitrat of mercury, the mercurial fo¬ 
lution may be evaporated to dryneffs : pulverize the mafs 
in a glafs mortar, put it into one matrafs or feveral; place 
them in a fand-bath ; heat the vefiels, and calcine the 
contents, till they prefent an orange colour on the fur- 
face; let the vefleis cool, and then break them : the con¬ 
tained matter will be found in layers of different colours; 
the under part of a bright red, the upper part orange 
colour. Then pulverize the red part, which is the red 
oxyd of mercury. Melt this oxyd under the blow-pipe 
with pholphoric glafs, and it communicates various co¬ 
lours to it. Mercurial nitrat diftiiied in a retort affords 
a fub-acid phlegm, and nitrous gas at firft, after which 
it becomes red oxyd ; and a ftronger heat being applied, 
occafions a large quantity of vital air, with a final! por¬ 
tion of azotic gas, to be dilengaged, the mercury being 
fublimed in the metallic form. This fait is folubie in 
diftiiied water, in a larger quantity when boiling, than 
in the cold, and confequently cryftallizes by cooling. 
When this fait is diftblved in water, a portion remains, 
which is of a yellowifh colour, and is not taken up. Mon- 
net calls this matter nitrous turbith, and obferves, that a 
larger quantity may be obtained by boiling water. If it 
be intended that the mercurial nitrat fhall be entirely 
difToived, water muff be employed, in which aqua fortis 
-muft be poured, until the precipitate appears. We have 
obferved, that when boiling water is poured on the purelt 
nitrat of mercury, it immediately becomes yellow, and 
affords an. oxyd of a deep colour,'which, when expofed 
to fire, becomes red more quickly than that which is 
made by tne fulphuric acid. 
Barytes, ftrontian, niagnefki> lime, and alkalis, decom- 
poffe nitrat of mercury, and precipitate the metal in the 
ftate of oxyd. Tlieie precipitates are- oS different colours, 
weight, 
