Encyclopaedia Britannica, or, a Dictionary of arts, sciences, and miscellaneous literature : enlarged and improved. Illustrated with nearly six hundred engravings > Volume 5, BUR-CHI

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Lids, gravity Is not known. It ha* an acid, pungent tafte,
Sj-f— not different from phofphoric acid. It alfo reddens
|jg vegetable blue colours.
yi:i) of 3. Phofphorous acid is not altered by light.
When expofed to heat in a retort, part of the water
combined with it is firft driven off; and wrhen it is con¬
centrated, bubbles of air fuddenly rife to the furface,
and colleft in the form of white fmoke, and fometimes
inflame, if there be any air in the apparatus. If the
experiment be made in an open veffel, each bubble of
air, when it comes to the furface, produces a vivid de¬
flagration, and diffufes the odour of phofphorated hy¬
drogen gas. This inflammable gas continues to be
evolved for a long time, and when the aftion ceafes,
phofphoric acid only remains behind. It ought to be
obferved, that the phofphorated hydrogen gas is not
difengaged till the phofphorous acid is concentrated and
brought to a high temperature, which feems to prove
that the phofphorus which is not faturated with oxy¬
gen, ftrongly adheres to it.
4. There is little attraction between oxygen and
phofphorous acid, which feems to be owing to the
great affinity between phofphorus and phofphoric acid.
It abforbs, however, very flowly, a fmall quantity of
oxygen ; and even after long boiling, it is not com-
90 pletely converted into phofphoric acid.
S'bgen. 5. Hydrogen gas has no aftion on phofphorous acid $
but this acid is decompofed at a red heat, by means of
charcoal, which feparates from it a greater quantity
of phofphorus than from phofphoric acid. There is no
aCtion between thefe bodies in the cold. Sulphur has
no aCtion on this acid at the ordinary temperature of
the atmofphere, and they cannot be combined by
means of heat, becaufe the phofphorus is diffipated
before it unites wdth the fulphur.
Of lids. 6. There is no aCtion between phofphorous acid and
fulphuric acid in the cold •, but when they are heated
together to the boiling temperature, the phofphorous
acid deprives the fulphuric of part of its oxygen, and
is converted into phofphoric acid, while part of the ful¬
phuric acid, thus decompofed, is difengaged in the
flate of fulphurous acid gas. Phofphorous acid pro¬
duces a limilar effeCt on nitric acid. The phofphorus
is converted into phofphoric acid, and part of the ni-
Ij52 trie acid is converted into nitrous gas.
7. This acid is compofed of the fame conftituent
parts as the phofphoric, and is confldered by fome as
Cm'ifs°y t^ie phofphoric acid holding in folution a fmall quanti-
Cb tom. ty of phofphorus *.
”■ 85. 8. Phofphorous acid forms compounds with alkalies,
pearths, and metallic oxides, which are known under
the name of phofphites.
9. The order of its affinities is the following.
CHEMISTRY.
Sect. XII. Of CaheoKic Acih,
93
'bounds.
94
:Ues.
At
Lime,
Barytes,
Strontites,
Potafh,
Soda,
Ammonia,
Glucina,
Alumina,
-Zirconia,
Metallic oxides.
1. When a piece of charcoal, in a (late of ignition,
is plunged into a jar of oxygen gas, it burns with great
brilliancy j and after the combuftion has ceafed, the 595
air in the veffel is totally changed. If a little water is *'orniatlon*
introduced into the jar, and agitated, the air combines
with it j and this water, when examined, exhibits
acid properties. This is carbonic acid. It is formed
by the combination of carbone and oxygen. This is
one of the molt important acids, both on account of
its numerous combinations, and alio on account of the
difeovery of it having occalioned a total revolution in
chemical fcience.
2. It was regarded by the ancients, on account of
the noxious eftefts which it produced, as a peltilenti&L
vapour, and they gave it the name of fpintus lethalis. 596
Paracelfus and Van Helmont confldered it as a peculiar Names,
matter, to which they gave the name, Jpintus fylve-
Jiris, or gas. Hales, although he confldered it merely
as contaminated air, diitinguilhed it by the name of
Jixed air, becaufe it entered into the compofition of
many bodies. Dr Black demonitrated, that it is a
peculiar fubitance, different from the air $ that lime,
magnefia, and the alkalies, were deprived of their
cauiticity, by being combined with this air, and there¬
fore he gave it the name of Jixed air. It was after¬
wards found by the experiments of Keirand Bergman,
to be an acid, and hence Bergman gave it the name
of aerial acid. The nature and properties of this acid
were inveftigated by many chemical philofophers, and
from them it received various names, as mephitic acid,
calcareous or cretaceous acid, thus diftinguiffied from
its effefts, or from the fubftances from which it w'as
obtained. In the prefent chemical nomenclature it
has the name of carbonic acid, from its bafe carbone.
3. For fome time after the difeovery of the differ-fup3
ence between carbonic acid and common air, and its poled fun-
properties as an acid, it was confldered by many as apk.
Ample elementary fubftalice, and it was regarded as
the acidifying principle. In the progrefs of inveftiga-
tion it was found to be a compound fubftance, and
that oxygen -was one of its conliituent parts, and it was
generally believed that phlogifton conftituted the other.
When hydrogen was fubftituted for phlogifton, it was
fuppofed that oxygen and hydrogen conftituted car¬
bonic acid. The difeovery of Mr Cavendilh, proved
that water, not carbonic acid, was the product of
the combination of oxygen and hydrogen. But the
experiments of Lavoifier have eftablilhed the fa<ft, and
placed it beyond difpute. He demonftrated that the
weight of the carbonic acid which was obtained, was
exactly equal to the quantity of the oxygen and char¬
coal which had difappeared. s
4. Carbonic acid may be obtained by taking a quan- Method of
tity of chalk or limeftone, or marble, and reducing obtaining
them to a coarfe powder. Introduce it into a matrafs,
pour over it a quantity of diluted fulphuric or nitric
-acids ; a violent effervefcence takes place, carbonic
acid gas is difengaged, which paffes over, and may be
received in veffels in the ufual way. The chemical
action that takes place in this change muft be obvious.
The affinity of the fulphuric acid for the lime is ftrong-
3 LJ 2 er