CHEMISTRY.
_INTRODUCTION._
WHAT CHEMISTRY IS—THE ELEMENTS—METALLIC AND NON-METALLIC—ATOMIC
WEIGHT—ACIDS—ALKALIS—BASES—SALTS—CHEMICAL COMBINATION AND STUDY.
Chemistry is the science of phenomena which are attended by a change
of the objects which produce them. We know that when a candle burns,
or when wood is burned, or even a piece of metal becomes what we term
“rusty,” that certain chemical changes take place. There is a change
by what is termed chemical action. Rust on iron is not iron; it is
oxide of iron. The oxygen of the air causes it. So we endeavour, by
Chemistry, to find out the nature of various bodies, their changes, and
the results.
[Illustration: Fig. 301.—The Laboratory.]
In nature we have simple and compound bodies. The former are called
ELEMENTS. We must not confuse these elements with the so-called
elements—earth, air, fire, and water. These are really compound bodies.
An element is a substance or a gas which is not composed of more than
one constituent; _it is itself_—a compound of perfectly identical
particles. Every “compound” body, therefore, must be made up of some of
the elements, of which there are sixty-five. These bodies are divided
into non-metallic and metallic elements, and all bodies are composed
of them, or are these bodies themselves. The list is as follows. The
non-metallic elements are “metalloids.” We have omitted fractions from
the weights, on which chemists differ.
TABLE OF ELEMENTS WITH THEIR CHEMICAL SYMBOLS AND COMBINING WEIGHTS.
Non-Metallic Atomic or
Elements. Symbols. Combining Derivation of Name.
Weights.
Oxygen O 16 Gr. Oxus, acid; gennaō, to make.
Hydrogen } { H 1 Gr. Udor, water; gennaō, to make.
Nitrogen } Gaseous { N 14 Gr. Natron, nitre; gennaō, to make.
Chlorine } {Cl 35 Gr. Chloros, green.
Iodine } { I 127 Gr. Ioeides, violet.
Fluorine } { F 19 Fluor spar, the mineral.
Carbon } { C 12 Lat. Carbo, coal.
Sulphur } { S 32 Lat. Sulphurium.
Phosphorus } { P 31 Gr. Phos, light; pherein, to carry.
Arsenic* } Solid{ As 75 Gr. Arsenicon, potent.
Silicon } { Si 28 Gr. Silex, flint.
Boron } { B 11 Gr. Borax, Arab., baraga, to shine.
Selenium } { Se 79 Gr. Selene, the moon.
Tellurium } { Te 129 Lat. Tellus, the earth.
Bromine Fluid 80 Gr. Bromos, offensive smell.
METALS.
Name. Symbols. Atomic or Derivation.
Combining
Weights.
Aluminium Al 27 Lat. Alumen, alum.
Antimony (Stibium) Sb 122 Gr. Anti, against; minos, one.
[Arsenic] As 75 (Not known.)
Barium Ba 137 Gr. Barsù, heavy.
Bismuth Bi 210 Ger. Weissmuth, white matter.
Cadmium Cd 112 Gr. Cadmeia, calamite.
Cæsium Cs 133 Lat. Cæsius, sky-blue.
Calcium Ca 40 Lat. Calx, lime.
Cerium Ce 141 The planet Ceres.
Chromium Cr 52 Gr. Chroma, colour.
Cobalt Co 58 Ger. Kobald, a sprite.
Copper Cu 63 Lat. Cuprum (Cyprium), Cyprus.
Didymium D 147 Gr. Didumos, twins.
Erbium E — Ytterby in Sweden.
Gallium Ga 70 (Not known.)
Glucinum Gl 9 Gr. Glukos, sweet.
Gold Au 197 From Hebrew, to shine (doubtful).
Indium In 113 Indigo colour.
Iridium Ir 198 Gr. Iris, rainbow.
Iron Fe 56 Hebrew, to meet (doubtful).
Lanthanum La 139 Gr. Lanthanein, to lie hid.
Lead Pb 207 (Plumbum) malubodos (galena).
Lithium Li 7 Gr. Lithos, stone.
Magnesium Mg 24 Magnesia, Asia Minor.
Manganese Mn 55 Mangana, E. I. (or Magnesia).
Mercury Hg 200 Heathen deity (quick).
Molybdenum Mo 96 Gr. Molybdena, lead ore, like lead.
Nickel Ni 58 Ger. Kupfer nikel, false copper.
Niobium (Columbium) Nb 94 Columbite.
Osmium Os 199 Osme, an odour.
Palladium Pl 106 Pallas, Minerva.
Platinum Pt 197 Spanish, platina, little silver.
Potassium (Kalium) K 39 Potash.
Rhodium Rh 104 Gr. Roda, rose.
Rubidium Rb 85 Lat. Rubidus, red.
Ruthenium Ru 104 (Not known.)
Silver (Argentum) Ag 108 Hebrew, money.
Sodium (Natrium) Na 23 Salsoda plant.
Strontium Sr 87 Strontian, N.B.
Tantalum Ta 182 Tantalite mineral.
Terbium Tr — (Not known.)
Thallium Tl 204 Gr. Thallos, green twig.
Thorium Th 230 Thor, deity.
Tin (Stannum) Sn 118 (Not known.)
Titanium Ti 50 Titans.
Tungsten (Wolfram) W 184 Swedish.
Uranium U 240 Urania.
Vanadium V 51 Vanadis, a goddess in Sweden, etc.
Yttrium Y 93 (Not known.)
Zinc Zn 65 Ger. Zinken, nails.
Zirconium Zr 89 Ger. Zircon, four-cornered (Ceylon).
*Arsenic is sometimes considered a non-metallic and sometimes a
metallic substance.
The term “combining weight” requires a little explanation. We are
aware that water, for instance, is made up of oxygen and hydrogen in
certain proportions. This we will prove by-and-by. The proportions are
in eighteen grains or parts of water, sixteen parts (by weight) of
oxygen, and two parts (by weight) of hydrogen. These are the weights
or proportions in which oxygen and hydrogen combine to form water,
and such weights are always the same in these proportions. Chemical
combination always occurs for certain substances in certain proportions
which never vary in those compounds, and if we wish to extract oxygen
from an oxide we must take the aggregate amount of the combining
weights of the oxide, and we shall find the proportion of oxygen; for
the compound always weighs the same as the sum of the elements that
compose it. To return to the illustration of water. The molecule of
water is made up of one atom of oxygen and two atoms of hydrogen. One
atom of the former weighs sixteen times the atom of the latter. The
weights given in the foregoing table are _atomic_ weights, and the law
of their proportions is called the Atomic Theory.
An _atom_ in chemistry is usually considered the smallest quantity of
matter that exists, and is indivisible. A _molecule_ is supposed to
contain two or more atoms, and is the smallest portion of a compound
body. The standard atom is hydrogen, which is put down as 1, because
we find that when one part by weight of hydrogen is put in combination,
it must have many more parts _by weight_ of others to form a compound.
Two grains of hydrogen, combining with sixteen of oxygen, makes
eighteen of water, as we have already seen.
Take an example so plainly given by Professor Roscoe, remembering that
the numbers in our table represent the fixed weight or proportion by
weight in which the simple body combines. The red oxide of mercury
contains sixteen parts by weight of oxygen to two hundred parts by
weight of mercury (we see the same numbers in the table); these
combined make two hundred and sixteen parts of oxide. So to obtain 16
lbs. of oxygen we must get 216 lbs. of the powder. It is the same all
through, and it will be found by experiment that if any more parts
than these fixed proportions be taken to form a compound, some of that
element used in excess will remain free. Lime is made up of calcium and
oxygen. We find calcium combining weight is forty, oxygen sixteen. Lime
is oxide of calcium in these proportions (by weight).
When we wish to express the number of atoms in a compound we write the
number underneath when more than one; thus water is H_{2}O. Sulphuric
acid H_{2}SO_{4}. As we proceed we will give the various formulæ when
considering the chief elements.
In chemistry we have acids, alkalis, and salts, with metallic oxides,
termed _bases_, or bodies, that when combined with _acids_ form
_salts_. Alkalis are bases.
ACIDS are compounds which possess an acid taste, impart red
colour to vegetable blues, but lose their qualities when combined with
bases. Hydrogen is present in all acids. There are insoluble acids.
Silicic acid, for instance, is not soluble in water, has no sour taste,
and will not redden the test litmus paper. On the other hand, there are
substances (not acids) which possess the characteristics of acids, and
most acids have only one or two of these characteristics.
Thus it has come to pass that the term “acid” has in a measure dropped
out from scientific nomenclature, and salt of hydrogen has been
substituted by chemists. For popular exposition, however, the term is
retained.
ALKALIS are bases distinguished by an alkaline taste. The
derivation is from Arabic, _al-kali_. They are characterized by certain
properties, and they change vegetable blues to green, and will restore
the blue to a substance which has been reddened by acid. They are
soluble in water, and the solutions are caustic in their effects.
Potash, soda, and ammonia are alkalis, or chemically, the oxides of
potassium, sodium, ammonium, lithium, and cæsium are all alkalis.
Potash is sometimes called “caustic” potash. There are alkaline earths,
such as oxides of barium, strontium, etc. _Bases_ may be defined as the
converse of acids.
Acids and alkalis are then evidently opposite in character, and yet
they readily combine, and in chemistry we shall find that unlike bodies
are very fond of combining (just as opposite electricities attract
each other), and the body made by this combination differs in its
properties from its constituents.
SALTS are composed of acids and bases, and are considered
neutral compounds, but there are other bodies not salts, which likewise
come under that definition—sugar, for instance. As a rule, when acids
and alkalis combine _salts_ are found.
Chemical phenomena are divided into two groups, called _inorganic_ and
_organic_, comprising the simple and compound aspects of the subject,
the elementary substances being in the first, and the chemistry of
animals or vegetables, or organic substances, in the latter. In the
inorganic section we shall become acquainted with the elements and
their combinations so often seen as _minerals_ in nature. Chemical
_preparations_ are artificially prepared. To consider these elements we
must have certain appliances, and indeed a laboratory is needed. Heat,
as we have already seen, plays a great part in developing substances,
and by means of heat we can do a great deal in the way of chemical
decomposition. It expands, and thus diminishes cohesion; it counteracts
the chemical attraction. Light and electricity also decompose chemical
combinations. But before proceeding it will be as well to notice a few
facts showing how Nature has balanced all things.
The earth, and its surrounding envelope, the atmosphere, consist of a
number of elements, which in myriad combinations give us everything we
possess,—the air we breathe, the water we drink, the fire that warms
us, are all made up of certain elements or gases. Water, hydrogen and
oxygen; air, oxygen and nitrogen. Fire is combustion evolving light and
heat. Chemical union always evolves heat, and when such union proceeds
very rapidly fire is the result.
In all these combinations we shall find when we study chemistry that
not a particle or atom of matter is ever lost. It may change or combine
or be “given off,” but the matter in some shape or way exists still.
We may burn things, and rid ourselves, as we think, of them. We do rid
ourselves of the compounds, the elements remain somewhere. We only
alter the _condition_. During combustion, as in a candle or a fire,
the simple bodies assume gaseous or other forms, such as carbon, but
they do not escape far. True they pass beyond our ken, but nature is so
nicely balanced that there is a place for everything, and everything
is in its place under certain conditions which never alter. We cannot
_destroy_ and we cannot _create_. We may prepare a combination, and
science has even succeeded in producing a form like the diamond—a
crystal of carbon which looks like that most beautiful of all crystals,
but we cannot make a diamond after all. We can only separate the
chemical compounds. We can turn diamonds into charcoal it is true,
but we cannot create “natural” products. We can take a particle of
an element and hide it, or let it pass beyond our ken, and remain
incapable of detection, but the particle is there all the time, and
when we retrace our steps we shall find it as it was before.
This view of chemistry carries it as a science beyond the mere holiday
amusement we frequently take it to be. It is a grand study, a study
for a lifetime. Nature is always willing, like a kind, good mother as
she is, to render us up her secrets if we inquire respectfully and
lovingly. The more we inquire the more we shall find we have to learn.
In these and the following pages we can only tell you a few things,
but no one need be turned away because he does not find all he wants.
We never do get all we want in life, and there are many first-rate
men—scientists—who would give “half their kingdom” for a certain bit
of knowledge concerning some natural phenomena. There are numerous
excellent treatises on chemistry, and exhaustive as they are, at
present they do not tell us all. Let these popular pages lead us to the
study of nature, and we shall find our labour far from onerous and full
of interest, daily increasing to the end, when we shall know no more of
earth, or chemistry.
As a preliminary we will put our workshop aside, and show you something
of _Chemistry without a Laboratory_.