Staunton spectator, and general advertiser. [volume] (Staunton, Va.) 183?-1849, 1845-10-23
A G. D I q U u N U IG u o
FROM tar LEXINGTON GAZETTE
Notes Of course Of lectures on Agricultural Chem.
istry delivered before an Association Of Practi.
cal Farmers,
BY GEORGE ID. ARMSTRONG,
PROFESSOR OF CHEMISTRY IN WAsHINGToN COLLEGE,
LEXINGTON, VA.
LECTURE II.

PROFESSOR OF CHEMISTRY WAsHINGroS COLLEGE
LEXINGTON, Va
LECTURE II.
General Lars of Chemical attraction continued -
| chemical nomenclature; chemical symbols.
Va Some substances are capable of chemica
union IN any proportions whatever; others in an,
proportions within certain limits; others still, il
a few definite proportions only.
Alcohol and water furnish an instance of the
first kind "a drop of alcohol may be combined
with gallon of water, or a drop of water with .
gallon of alcohol. Common table salt and water
furnish an instance of The second kind 100 grs
! OF water vii! combine with dissolve any ia
tlty of table-sat not exceeding grs.j its solvent
powers then cease. Oxygen and Hydrogen fur
nlsh an instance Of the third kind 81 or. of Hy.
drogen will unite with or I6 grs. OF Oxygen,
but In no other proportion whatever. The fist
TWO OF these classes Of compounds thus formed
are termed indefinite compounds, the last definite
compounds.
Indefinite compounds seldom differ much In
their properties from the substances of which
they are composed, and, general thing, read
~ undergo decomposition. Indeed, some of our
aolest chemists regard them as simply mechanic
cal admixtures, and not as chemical compounds
al all giving to them the name of mixtures
where both substances are of the same FORM j. e.
both solids, liquids gases and the name of
solutions where one of them is luuid and the
other either solid or gas. The latter view of
The case seems 10 be the more simple one, and al
though have thus far Tin accordance with the
practice OF those chemists whose works are in
most general circulation in this country spoken
oil these classes OF substances as chemical COM
POUNDS, shall hereafter use that expression i'm
Its restricted sense, as applicable to definite COM
POUNDS only. Gases of solution, without incSease
In ouik' are explained by reference to the porosi-
~ OF matter; the particles Of the dissolved body
being believed to be slowed away in the pores of
the solvent liquid. When a liquid has dissolved
as much of solid or gas as it is capable of dis
solving, II is said to be saturated.
VII. Definite compounds are invarable in
composition, and the proportions in which their
elements unite can be expressed in numbers.
water, formed by artificial means to-day, and
that formed at the creation, are Identical i'm their
composition; being composed of Hydrogen and
oxygen In the same proportions, the numbers
expressing that proportion being part by weight
OF hydrogen to parts by weight of OXYGEN
regular chemical compounds often occur in ma
lure mechanically mixed with certain other sub
stances termed Impurities, and thus furnish The
only apparent exceptions to this law; there are
no real exceptions. Thus, limestone is met with
varying much In composition, because common
limestone consists OF mixture of carbonate o.!
lime lpure limestcne] and variable quantity of
siiex' clay and other impurities; whilst carbo-
nate OF lime is intariable in composition. ALWAYS
consisting of 2s9 parts by weight of lime to 80
Of carbonc acid:
VIII. Where one substance unites chemical
" WIN several others, the same number, or some
simple multiple of that number, j. e. twice or
thrice or Tour times, &c., that number which ex-
presses the proportion in which it combines with
one OF those substances, will express the proper
'lon IN which II combines with each of the Others
thus, 3 parts by weight of Oxygen unite with
OF Hydrogen:-l of Hydrogen with l6 of Sui
phur IS of Oxygen with l6 of Sulphur.
ms eighth law, as well as the two preceding
Ones admit OF a very simple explanation in ac-
cordance with what is termed the atomic theory
respecting the constitution of matter; a theory
wh'ch at the present day is universally received
among chemists. According to this theory, mat
'er' instead OF being infinitely divisible, as was
al one time believed, is made up of ultimate par-
'icies In their very nature indvisible, and hence
called atoms. If we admit the existence of these
atoms, and that the atoms of different kinds of
nna,'ei aiher from each other in weight (and such
Is the theory) these laws admit of a very simp!e
explanation. If the atom of Oxypen WEIGHS g
times as much as that of Hydrogen, and that of
sulphur 10 times as much as that of Hydrouen
we see at once why parts of Oxygen unite with
OF hydrogen, or with I6 of Sulphur, such COM
pounds being composed of | atom of the one and
atom OF the other did they unite in any other
proportions, such as or 6 of Oxygen to l of Hv-
oro9ep, 1t would be necessary that the atom of
oxygen should be divided, and this the theory
assumes to be impossible.
inese numbers which express the proportion
I'D which different substances unite with each o.
ther, are called their proportional numbers and,
as The combining proportion of one substance is,
as IL were' equivalent TO that of another, and may
be substituted for it in combination, they are fire.
quently called equivaiem numbers or chemical G.
qWodentS; and further, as they express the TeIa-
i've weights OF the atoms of different kinds of
mat'er III we admit the existence of such atofns)
they are sometimes called the atomic aDeiphts OF
substances.
The eighth law applies to compound as well
as simple substances. The chemical eouipnieaf mr.
atomic ,0eigM of compound substance is found by
adding together those Of its elements. Thus
ouIPhurlc Acid is composed of one atom Of Sui
phur l6] and three atoms Of Oxygen rs times 8
are "a It's atomic weight is 1 6 added TO 81 that
is 40.
Where one substance untes in several propor.
lions with another, the compound generally con-
ssts OF atom of the one united with l. 2 g. A.
&c.s oil the other; or 2 atoms of the one united
with |, 2, 3, d, &C., Of the other; in very few
instances only do we meet with more complex
ratios than these in the mineral kingdom in the
vegetable and animal kingdoms they are more
common.
! a knowledge Of these chemical equivalents or
atomic weights IS of great practical value to the
chemists, and this, for several reasons. LIST. By
remembering the equivalents Of few elementary
substances, the exact composition Of vast num-
Der OF compounds may be calculated with facItv.
Ind. The exact quantity of substance required
70 combine with given quantity Of any other
substance can be determined with certainty. 3rd.
Inc exact result Of any decomposition can be
made matter Of calculation
/ IN LAW. Gases unite by volume in very sim
pie ratios, generally as 10 l., TO Q, to 4, or