160 
spring, and is frequently gathered for that 
purpose ; but it is said to be hurtful to 
sheep.” Mr. day relates the case of a man, 
his wife, and three children, who experi- 
enced highly deleterious effects from eating 
it tried with bacon ; but this was probably 
when the spring was more advanced, and 
the plant had become acrimonious. When 
steeped in water, it affords 'a fine deep-blue 
colour. Sheep and goats eat -it ; but cows 
and horses refuse it. 
MERCURY, called also quicksilver, 
was known in the remotest ages, and seems 
to have been employed by the antients in 
gilding and in separating gold from other 
bodies, just as it is by the moderns. 
Its colour is white, and similar to that of 
silver ; hence the names hydrargyrus, ar- 
gentum vivum, quicksilver, by which it has 
been known in all ages. It has no taste nor 
smell. It possesses a good deal ot' brilliancy ; 
and when its surface is not tarnished, makes 
a very good mirror. Its specific gravity is 
13.568. At the common temperature of the 
atmosphere, it is always in a state of fluidity. 
In this respect it differs from ail other metals. 
But it becomes solid when exposed to a suf- 
ficient degree of cold. The temperature 
necessary for freezing this metal is — 39°, 
as was ascertained by the experiments of Mr. 
Macnab at Iiudspn’s-bay. The congelation 
of mercury was accidentally discovered by 
the Petersburgh academicians in 1759. Tak- 
ing the advantage of a very severe frost, 
they plunged a thermometer into a mixture 
of snow and salt, in order to ascertain the 
degree of cold. Observing the mercury sta- 
tionary, even after it was removed from the 
mixture, they broke the bulb of the thermo- 
meter, and found the metal frozen into a 
solid mass. 'Phis experiment has been re- 
eated very often since, especially in Britain. 
lercury contracts considerably at the instant 
of freezing ; a circumstance which misled 
the philosophers who first witnessed its con- 
gelation. The mercury in their thermome- 
ters sunk so much before it froze, that they 
thought the cold to which it had been ex- 
posed, much greater than it really was. It 
was in consequence of the rules laid down 
by Mr. Cavendish, that Mr. Macnab was en- 
abled to ascertain the real freezing point of 
the metal. 
• Solid mercury may be subjected to the 
blows of a hammer, and may be extended 
without breaking. It is therefore malleable ; 
but neithe* the degree of its malleability, nor 
its ductility, nor its tenacity, has been as- 
certained. 
Mercury boils when heated to 660°. It 
may therefore lie totally evaporated, or dis- 
tilled from one vessel into another. It is by 
distillation that mercury is purified from va- 
rious metallic bodies-, with which it is often 
contaminated. The vapour of mercury is in- 
visible and elastic like common air ; like 
air, too, its elasticity is indefinitely increas- 
ed by heat, so that it breaks through the 
strongest vessel. GeoffVov, at the desire of 
an alchymist, inclosed a quantity of it in an 
iron glob e, strongly secured by iron hoops, 
and put the apparatus into a furnace. Soon 
after the globe became red-hot, it burst with 
all the violence of a bomb, and the whole of 
the mercury was dissipated. 
Mercury is not altered by being kept un- 
der water. When exposed to the air, its 
MERCURY. 
surface is gradually tarnished, and covered < 
with a black powder, owing to its combining i 
with the oxygen of the atmosphere. But j 
this change goes on very slowly, unless the | 
mercury is either heated or "agitated, by j 
shaking it, for. instance, in a large bottle full 
of air. By either of these processes, the me- 
tal is converted into an oxide : by the last, 
into a black-coloured oxide ; and by the first, 
into a red-coloured oxide. This metal does 
not seem to be capable of combustion. 
The oxides of mercury at present known 
are four in number : 
1. The protoxide was first described. with 
accuracy by Boerhaave. lie formed it by 
putting a Title mercury into a bottle, and 
tying it to the spoke of a mill-wheel. By 
the constant agitation which it thus under- 
went, it was converted into a black powder, 
to which he gave the name of ethiops per 
ic- This oxide is readily formed by agitat- 
ing impure mercury in a phial. It is” a black 
powder without any of the metallic lustre, 
has no taste, and is insoluble in water. Ac- 
cording to the experiments of Fourcroy, if is 
composed of 96 parts of mercury and 4 of 
oxygen. When this oxide is exposed to a 
strong heat, oxygen gas is emitted, and the 
mercury reduced to the metallic state. In a 
more moderate heat it combines with an ad- 
ditional dose of oxygen, and assumes a red 
colour. 
2. When mercury is dissolved in nitric 
acid without the assistance of heat, and the 
acid is made to take up as much mercury as 
possible, it has been demonstrated, by the 
experiments of Mr. Chenevix, that it com- 
bines in that case with 10.7 per cent, of oxy- 
gen. Of course an oxide is formed, com- 
posed of 89.3 mercury and 10.7 xixvgen. 
This is the deutoxide of mercury. This ox- 
ide cannot be separated completely from the 
acid which holds it in solution without under- 
going a change in its composition ; of course 
we are at present ignorant of its colour and 
other properties. Indeed it is very probable 
that it is the same with the black oxide just 
described under the name of protoxide; but 
this has not yet been proved in a satisfactory 
manner. 
3. When mercury, or its protoxide, is ex- 
posed to a heat of about 600°, it combines' 
with additional oxygen, assumes a red co- 
lour, and is converted into an oxide, which, 
in the present state of our knowledge, we 
must consider as a tritoxide. This oxide 
may be formed two different ways: 1. By 
putting a little mercury into a flat bottomed 
glass bottle or matrass, the neck of which is 
drawn out into a very narrow tube, putting 
the mattrass into a sand-bath, and keeping it 
constantly at the boiling point. The height 
of the mattrass, and the smallness of its 
mouth, prevent the mercury from making 
its escape, while it affords free access to the air. 
The surface of the mercury becomes gradually 
black, and then red, by combining with the 
oxygen of the air : and at the end of several 
months the whole is converted into a red 
powder, or rather into small crystals, of a 
very deep red colour. The oxide, when thus 
obtained, was formerly called precipitate per 
se. 2. When mercury is dissolved,, in nitric 
acid, evaporated to dryness, and then ex- 
posed to a pretty strong heat in a porcelain 
cup, it assumes, when triturated, a brilliant 
red colour. The powder thus obtained was 
! formerly called red precipitate, and possesses 
j exactly »the properties ot the oxide obtained 
j By the former process. 
! This oxiue has an acrid and disagreeable 
| taste, possessing poisonous qualities, and acts 
as an feseharotie when applied to any pail of 
the skin, it is somewhat soluble in water. 
AY hen triturated with mercury it gives out 
part of its oxygen, and the whole mixture is 
converted into protoxide or black oxide of 
mercury. \Y hen heatedalong with zinc, or tin 
filings, it sets these metals on lire. Accord- 
ing to Fourcroy,. it is composed ol 92 parts of 
mercury and 8 of oxygen. ' But the analysis 
of Mr. Chenevix, to lie described hereafter, 
gives, for the proportion of its component 
parts, 83 parts of mercury and 15 parts of 
oxygen. 
The red oxide of mercury, prepared in 
the usual way, is not pure, but always con- . 
tains a portion of nitric acid. If we dissolve j 
it in muriatic acid, and precipitate it again, 
it falls in the stale of a white powder, and re- \ 
tains a portion of muriatic acid. It was in 
this state that it was examined by Chenevix. | 
The difficulty of procuring this oxide in I 
a state of purity, and the uncertainty respect-1 
ing the proportion of acid which it retains, j 
may, in some measure, account for the differ- j 
ent results obtained by different chemists in 
their attempts to ascertain its proportions. 
4. Fourcroy has observed, that when oxy- 
muriatic acid gas is made to pass through the 
'fed oxide of mercury, it combines with an 
additional dose of oxygen, and is converted 
into a peroxide; but as this peroxide cannot 
be procured in a separate state, we are igno- 
rant of its properties. 
Mercury does not combine with carbon or 
hydrogen; but it unites readily with sulphur 
and until phosphorus. 
V\ lien two parts of sulphur and one of mer-i 
cui y are triturated together in a mortar, the 
mercury gradually disappears, and the whole 
assumes the form of a black powder, for- 
merly called ethiops mineral. It is scarcely 
j ossibie by any process tocombina the sulphur 
and mercury so completely, that small' glo-' 
bules of the metal may not be detected by a 
microscope. When mercury is added slowly 
to its own weight of melted sulphur, and the 
mixture is constantly stirred, the same black 
compound is formed. 
Fourcroy had suggested, that in this com- 
pound the mercury is in the state of black 
oxide, absorbing the necessary portion of ox- 
ygen from the atmosphere dtuing’its combi- 
nation with the sulphur. But the late expe- 
riments ot Froust have shewn that this is not 
the case. Berthollet lias made it probable: 
that ethiops mineral contains sulphureted 
hyarogen. Hence we must consider it as 
composed or three ingredients, namely, mer- 
cury, sulphur, and sulphureted hydrogen. 
Such compounds are at present denominated 
by chemists hydrogenous sulphurets. Ethiops] 
mineral ot course is an hydrogenous snlplmvet 
otmercury. When this.substunce is heated, 
part of the sulphur is dissipated, and the 
compound assumes a deep violet colour. - 
When heated red-hot, it sublimes; and if 
a proper vessel is placed to receive it, a cake 
is obtained of a fine red colour. This cake 
was formerly called cinnabar; and when re- 
duced to a fine powder, is well known in 
commerce under the name of vermilion. It 
has been hitherto supposed a compound of 
