A Manual of the Chemistry of the Carbon Compounds

THE CARBON COMPOUNDS.
QUANTIVALENCE OF THE ELEMENTS.
CHEMICAL NATURE OF CABBON.
Elements combine either in the proportion of their combining
weights or in simple multiples of them. To explain this fact, we
assume with Dalton that matter is made up of small particles, which
are cliemicatty indivisible and are therefore called eJiemicai atoms. Of
these atoms there exist as many kinds as there are elements. Simple
bodies consist of the same kind of atoms, all of which have the same
weight, whilst the atoms of different elements possess different weights.
The ratio existing between these different weights is expressed by the
combining weights of the elements, which ate hence also called atomic
weights. By two or more heterogeneous atoms being joined together,
a chemical compound is formed. The smallest particle of such a
compound consists of a coalition of atoms, only capable of destruction
by chemical, not by mechanical means, and this is called a molecule.
The smallest portion of a simple body also consists of a group of
atoms or a molecule, not mechanically divisible.
As our unit for the atomic weights, we use that of hydrogen;
its molecule consisting of two atoms. The same element also serves
as the unit for the density of gases and vapours. It las now been
found that the densities of all gases and vapours are equal to half
their moleoular weights, and that, consequently, equal volumes of
different gases always contain the same number of molecules, or that
any molecule in the gaseous state occupies the same space as two
parts by weight of hydrogen.
When a chemical change occurs,certain atoms contained indifferent
molecules replace eaoh other. Formerly it was believed that one atom
always changed place with another, but we now know that this is
not the case, but that one atom of a certain element often replaces
two, three, or four atoms of other elements. Hence the atoms of
different elements differ in their qiumUvalence.
Hydrogen is distinguished amongst all the elements by its fornuii^
the most simple compounds, and for this reason this element is best
adapted for ascertaining the qnantivalence of other elements, of which
those forming volatile hydrides can be divided into tour groups:—
n_,Imm. Hydrogen Hydrogen Hydrogen Hydrogen
Hydrogen. Culorfto Bromide. loUide. Fluoride.
H) H) H| R\ H)
Hj Clj" BrJ IJ Fj
w«t«r Hydrogen Hydrogen Hydrogen
Water. Sulphide. Solenfio. Tellnnde.
H H H H
HJ° l HfU U U
S H/ Se HJ
B 2