oe 
BARTH. 
BARYTES. 
367 
causing the whole weight of the limb to be borne | glistening. Specific gravity, 43. It is composed 
by the other portions of the sole. Its chief fea- 
ture is a continuation of the common shoe round 
the heels; and its principal use is in cases of 
corn, sand-crack, and pumiced feet; but it requires 
to be made thick, and sometimes presses very in- 
juriously on the heels. 
BARTH. A warm enclosure or sheltered pas- 
ture for calves or lambs. 
BARTON, or Barxen. The yard of a farm- 
house. 
BARTSIA. A genus of ornamental annual 
plants, of the figwort tribe. Three species are 
natives of Great Britain ;—the viscous, growing 
in marshes, and having a yellow flower; the 
alpine, growing beside mountain streams, and 
having a purple flower; and the odontites, grow- 
ing on meadows and pastures, and having a pink 
flower. They grow to the height of from 6 to 9 
inches, and bloom in July. 
BARYTES. The name of one of the earths; 
from a Greek word signifying heavy, on account 
of the great weight of its acid combinations. It 
is procured either from the native sulphate of 
barytes, by exposing its powder to ared heat with 
charcoal, and by forming from the resulting sul- 
phuret a nitrate, which is decomposed by heat ; 
or from the native carbonate, by dissolving it in 
nitric acid, and, in like manner, subjecting it to 
heat. Thus obtained, barytes has a specific 
gravity of 4, is of a grey colour, has a caustic 
taste, and slakes on exposure to the air, like lime, 
falling to powder from the absorption of water. 
It is soluble in 25 parts at 60°, and in the pro- 
portion of nearly half its weight at 212°, The 
solution, on cooling, affords prismatic crystals. 
Its watery solution possesses, distinctly, alkaline 
properties, changing the vegetable blues to green, 
and acquiring a film upon its surface, when ex- 
posed to the air, from the absorption of carbonic 
acid. It operates asa virulent poison when taken 
into the stomach. To the flame of alcohol it im- 
parts a yellow colour, which, together with its 
great solubility in water, serves to distinguish it 
from the other earths. It is useful in chemical 
analysis, in consequence of its property of uniting 
by fusion with several of the earths and metallic 
oxydes, and rendering them soluble in acids or 
water. Barytes has been decomposed by the 
agency of galvanism, and ascertained to be the 
oxyde of a peculiar metal, to which Sir Humphrey 
Davy has given the name of barium. It has a 
white colour, with a metallic lustre, resembling 
that of silver. Exposed to the air, or thrown in- 
to water, it absorbs oxygen, and is converted into 
barytes.—It combines with the acids, and forms 
a variety of salts, two of which, the carbon- 
ate and the sulphate, are found abundantly in 
nature. The first of these’ is called, in mineral- 
ogy, Witherite, from Dr. Withering, its discoverer. 
It is commonly fibrous or bladed in its structure, 
occasionally including small cavities lined with 
minute crystals. It is whitish, translucent, and 
of barytes, 78, and carbonic acid, 22. Like all 
other salts of barytes (with one exception), the 
carbonate is a virulent poison, and has often 
proved fatal to domestic fowls and animals who 
have accidentally swallowed it, about the mines 
where it occurs. Its principal localities are in 
the north of England, where it is found in lead 
mines: it also occurs in Styria, Salzburg, and 
Siberia. It is used to obtain the pure barytes, 
and those salts of this earth which are employed 
as chemical tests, and for the purposes of scientific 
illustration—The sulphate of barytes, called, in 
mineralogy, heavy-spar, is found abundantly in 
almost every*country, usually accompanying ga- 
lena, or common lead ore, of which it frequently 
forms the gangue. It is often beautifully crystal- 
lized under a variety of forms, derived from a 
right rhombic prism of 101° 42’, and 78° 18’, but 
is more generally lamellar or compact. It pre- 
sents numerous colours, of which white is the 
most frequent. It is translucent, and sometimes 
transparent, capable of being scratched by the 
knife, and of a specific gravity of 4'7._ Like the 
artificial sulphate of barytes, it is insoluble, and 
is the only salt of this earth which is not poison- 
ous. It consists of 67 parts barytes, and 33 sul- 
phuric acid. It is employed, though less exten- 
sively, for the same purposes as the carbonate, 
and was formerly used, by Mr. Wedgewood, in | 
the manufacture of his beautiful jasper ware—A 
fibrous variety of heavy-spar, called Bolognian 
stone, and which occurs, imbedded in small nodu- 
lar masses, in a marl near Bologna, has the re- 
markable property of: becoming phosphorescent 
by calcination —The artificial sulphate of barytes 
formed by adding sulphuric acid to the carbonate 
of barytes, is employed for the purpose of paint- 
ing in water-colours, and is the most beautiful 
white now in use. It is known by the name of 
Permanent white. The same substance is much 
valued for marking bottles in chemical labora- 
tories, where the acid vapours destroy common 
ink, and for labelling articles kept in cellars and 
moist places. In order to be applied, it is mixed 
up with spirits of turpentine and linseed oil, to 
the consistence of common paint, when it is laid 
on with a brush. Ifa black marking material is 
preferred, this may be rendered so by the addi- 
tion of a little lampblack. The nitrate of barytes 
is formed by dissolving the native carbonate in 
diluted nitric acid, and crystallizes on evapora- 
tion, It is soluble in 10 or 12 parts of water, at 
60°, and in 3 or 4 parts at 212°.—The murvaie of 
barytes, in like manner, is produced by submitting 
the carbonate to the action of dilute muriatic 
acid. It is much more soluble than the nitrate. 
Solutions of both these salts are of great impor- 
tance in analytical processes, for the detection of 
sulphuric acid; the barytes forming, with that 
acid, an insoluble precipitate, while the nitric or 
muriatic acid neutralizes the base. The muriate 
of barytes is employed with advantage as a medi- 
A Tt 
