M U R 
M U R 
M U S 
MURIATIC ACID. This substance may 
be procured by the following process: Let a 
small pneumatic trough be procured, hollow- 
ed out of a single block of wood, about 14 
inches long, seven broad, and six deep. After 
jt has been hollowed out to the depth of an 
inch, leave three inches by way of shelf on 
one side, and cut out the rest to the proper 
depth, giving the inside of the bottom a 
circular form. Two inches from each end 
cut a slit in the shelf to the depth of an 
inch, and broad enough to admit the end- of 
small glass tubes, or the points of small re- 
torts. This trough is to be tilled with mer- 
cury to the height of one quarter of an inch 
above the surface of the shelf. Small glass 
jars are to be procured of considerable thick- 
ness and strength, and suitable to the size of 
the trough. One of them, being filled with 
mercury by plunging it into the trough, is to 
be placed on the shelf over one of the slits. 
It ought to be supported in its position ; and 
the most convenient method of doing that is 
to have a brass cylinder two inches high 
screwed into the edge of the trough, just op- 
posite to the border of the shelf. On the 
top of it are fixed two Hat pieces of brass, ter- 
minating each in a semicircle, moveable free- 
ly upon the brass cylinder, and forming to- 
gether a brass arm terminating in a circle, 
the centre of which is just above the middle 
of the slit in the shelf, when turned so as to 
be parallel to the edge of the shelf. This 
circle is made to embrace the jar: being 
formed of two distinct pieces, its size may be 
increased or diminished at pleasure ; and by 
means of a brass slider it is made to catch the 
jar firmly. 
The apparatus being thus disposed, two or 
three ounces of common salt are to be put 
into a small retort, and an equal quantity of 
sulphuric acid added ; the beak of the retort 
plunged below the surface of the mercury 
in the trough, and the heat of a lamp ap- 
plied to the salt in its bosom. A violent ef- 
fervescence takes place; and air-bubbles 
rush in great numbers from its beak, and 
rise to the surface of the mercury in a visible 
white smoke, which has a peculiar odour. 
After allowing a number of them to escape, 
till it is supposed that the common air which 
previously existed in the retort has been dis- 
placed, plunge its beak into the slit in the 
shelf over which the glass jar has been placed. 
The air-bubbles soon displace the mercury 
and fill the jar. The gas thus obtained is 
called muriatic acid gas. 
This substance, in a state of solution in 
water, was known even to the alchemists ; 
but in a gaseous state it was first examined 
by Dr. Priestley, in an early part of that il- 
lustrious career in which he added so much 
to our knowledge of gaseous bodies. 
1. Muriatic acid gas is an invisible elastic 
fluid, resembling common air in its mechani- 
cal properties. Its specific gravity, accord- 
ing to the experiments of Mr. Kirwan, is 
0.002315, or nearly double that of common 
air. Its smell is pungent and peculiar; and 
whenever it comes in contact with common 
air, it forms with it a visible white smoke. If 
a bottle of it is drawn into the mouth, it is 
found to taste excessively acid ; much more 
so than vinegar. 
2. Animals are incapable of breathing it, 
and when plunged into jars filled with it, they 
•lie instantaneously in convulsions. Neither 
will any combustible burn in it. It is re- 
markable, however, that it has a considerable 
effect upon the flame of combustible bodies ; 
for if a burning taper is plunged into it, the 
flame, just before it goes out, may be ob- 
served to assume a green colour, and the 
same tinge appears next time the taper is 
lighted. 
3. If a little water is let up into a jar filled 
with this gas, the whole gas disappears in an 
instant, the mercury ascends, fills the jar, and 
pushes the water to the very top. The rea- 
son of this is, that there exists a strong affi- 
nity between muriatic acid gas and water ; 
and whenever they come in contact, they 
combine afirl form a liquid, or, which is the 
same thing, the water absorbs the gas. Hence 
the necessity, of making experiments with 
this gas over mercury. In the water cistern 
not a particle of gas would be procured. 
Nay, the water of the trough would rush 
into the retort and fill it completely. It is 
this affinity between muriatic acid gas and 
water which occasions the white smoke that 
appears when the gas is mixed with common 
air. It absorbs the vapour of water which 
always exists in common air. The solution 
of muriatic acid gas in water is usually deno- 
minated simply muriatic acid by chemists. 
4. If a little of the blue-coloured liquid 
which is obtained by boiling red cabbage- 
leaves and water, is let up into a jar filled 
with muriatic acid gas, the usual absorption 
of the gas, takes place, but the liquid at the 
same time assumes a fine red colour. This 
change is considered by chemists as a cha- 
racteristic property of acids. 
5. Muriatic acid gas is capable of com- 
bining with oxygen. To obtain the combi- 
nation, we have only to put a quantity of the 
black oxide of manganese in powder into a 
retort, and pour over it liquid muriatic acid. 
Heat is then to be applied to the mixture, 
and the beak of the retort plunged under 
water. An effervescence takes place, and a 
green-coloured gas comes out at the beak of 
the retort, which may be received in the 
usual foamier in jars. This gas has been as- 
certained to be a compound of muriatic acid 
and oxygen. It is called oxy -muriatic acid, 
and will come under our consideration here- 
after. 
6. It does not appear from any experi- 
ments that have been hitherto made, that any 
of the simple combustibles are capable of 
combining with muriatic acid gas. Dr. 
Priestley found, that sulphur absorbed slowly 
about the fifth part of it. What remained 
was inflammable air, burning with a blue 
flame, and not absorbed by water. Pie found 
that phosphorus scarcely absorbed any sen- 
sible quantity of it, and that charcoal absorbed 
it very fast. Hydrogen gas does not produce 
any sensible change in it. Neither does it 
seem capable of being affected by azotic 
gas- ' 
Muriatic acid is capable of combining with 
two doses of oxygen only. With the first 
dose, it forms oxymuriatic acid; with the 
second, hyperoxymuriatic acid. The first 
of them ought, in strict propriety, to be 
termed an oxide rather than an acid. 
MUR [ATS. The muriats are a genus of 
salts which have been long known, and from 
which indeed the whole of the class have bor- 
rowed their name ; for to them belongs com- 
G g 2 
235 
mon salt, the most important and the most 
indispensably necessary of all the salts. They 
may be distinguished by the following pro- 
perties : 
When heated, they melt, and are volati- 
lized, at least in part, without undergoing de- 
composition. The first portions which fly off 
contain an excess of acid. 
Not in the least altered by combustibles, 
even when assisted by heat. 
Soluble in water. For the most part they 
raise the boiling-point of water. - 
Effervesce with sulphuric acid, and white 
acrid fumes of muriatic acid are disengaged. 
When mixed with nitric acid, they exhale 
the odour of oxymuriatic acid. 
MURRAIN, or Gargle, a contagious 
disease among cattle, principally caused by a 
hot dry season, or rather by a general pu- 
trefaction of the air, which begets an inflam- 
mation of the blood, and a swelling in the 
throat, that soon proves mortal, and is com- 
municated from one to another, though it 
generally goes no farther than to those of the 
same kind. 
The symptoms of this disease are, a hanging 
down and swelling of the head, abundance of 
gum in the eyes, rattling in the throat, a 
short breath, palpitation of the heart, stag- 
gering, a hot breath, and a shining tongue. 
MURRAYA, a genus of the class and or- 
der decandria monygvnia. The calyx is 
five-parted; corolla bell-shaped, with a neo- 
tarium encircling the germ; berry one-seeded. 
There is one species, a tree of the East la- 
dies. 
MUS, the rat, a genus of quadrupeds of 
the order glires. The generic character is, 
upper front-teeth wedge-shaped; grinders 
on each side three, sometimes only two ; 
clavicles or collar-bones in the skeleton. 
This numerous tribe constitutes a formi- 
dable phalanx against which mankind find it 
necessary to employ “the various artifices of 
extirpation, in order to lessen the ravages oc- 
casionally suffered by its depredations. In 
our own island, the black and the brown rats, 
the field and domestic mice, are the principal 
destroyers ; but in other parts of Europe, as 
well as in the hotter regions of Asia, Africa, 
and America, many other species, still more 
noxious and formidable, are" found. The dif- 
ferent kinds vary considerably in their man- 
ner of life, some confining themselves entire- 
ly to vegetable food, while others are polv- 
phagous, destroying with indiscriminate avi- 
dity almost any animal or vegetable substance 
to which they can gain access. Their pace 
is, in general, rather quick, and their most 
usual residence is in obscure subterraneous 
retreats, from which they principally emerge 
by night. They are of a prolific nature, and 
the females are furnished with numerous 
teats. Some species are migratory ; others 
local or attached to the same residence. 
Lastly, some are of an uncouth form and dis- 
agreeable appearance, Vvhile others are re- 
markable for the elegance of their colours. 
In the 12th edition of the System! Natur®, 
Linmeus included in this genus the jerboas, 
the cavys, and several other animals which 
are now formed into distinct genera. This 
mode of distribution might perhaps be car- 
ried still farther, the habit or appearance of 
some species differing very considerably from 
that of the major part of tlie tribe. 
