SILICON.
Silicon may well be considered important on account of its _quantity_
in the earth, if on no other. In an earlier chapter it has been shown
that oxygen exists in our globe—including its atmosphere and its
oceans—in an amount equal to about one-half of the weight of the whole.
Now silicon exists in a quantity equal to about one-fourth of this
entire weight. In the earth however, neither of these substances exists
in the uncombined form. These facts seem to involve as a necessary
consequence that they exist in the earth, to a large extent, combined
with each other; indeed this is found to be the case. The principal
earthy matter of our planet is the compound of silicon and oxygen,
existing either alone in the form of sand, quartz crystal and similar
minerals, or else in combination with other well-known abundant earth
materials, such as oxides of calcium, magnesium and aluminum. It has
already been stated that carbon is the characteristic element of
animal and vegetable matters; so silicon is the characteristic element
of mineral matters. Thus granite and similar archaic rocks contain
approximately twenty-five per cent of silicon.
In nature, silicon performs its important office as a constituent of
rock material, with a fitness that is referable largely to the high
degree of stability possessed by most of its compounds. The permanence
of the materials of the earth’s surface under the influence of heat,
and water, and frost, and similar agencies is an illustration of this
principle.
_Silicic oxide_ (SiO₂), occurs on our globe in many different forms of
which diatomaceous earth and rock crystal may be mentioned.
Diatomaceous earth is a powdery material found in abundant deposits in
many parts of the world. Its characteristic structure, when examined
under the microscope, reveals its nature; then it is seen to be made
up of the shells of minute vegetable organisms called diatoms. These
assume a great many beautiful forms, and some of them are checkered
all over with markings of such extreme fineness that they have been
used as test objects for trying the resolving power of the objectives
of microscopes. This kind of earth is employed, as has already been
stated, in the preparation of dynamite.
[Illustration: FIG. 95.—Diatomaceous earth as seen through the
microscope.]
Quartz sometimes occurs in colorless transparent masses of great beauty
and clearness called rock crystal. The amethyst is the same substance
slightly colored by compounds of the metal manganese, while quartz
exists of a variety of other shades, in some of which it is prized as
a gem. Quartz generally assumes forms of a hexagonal tendency: they
are often hexagonal prisms terminated by hexagonal pyramids.
[Illustration: FIG. 96.—Mass of natural quartz crystals.]
Quartz and the finer and purer varieties of sand are used largely in
the manufacture of glass. The silicic oxide here displays what may be
expressed as its acid tendencies; for in the manufacture of glass it is
fused with sodic carbonate, and then the silicic oxide displaces the
carbon dioxide from the sodic carbonate; as a result there is formed
what must be regarded as a true salt, or a mixture of salts, that in
the simplest kind of glass may be termed _sodic silicate_.
* * * * *
_Closing Words._ The course laid out in the preface is now terminated
with silicon, as there planned. From scientific considerations, this
is a natural ending; it seems to be appropriate on another account
also. After the reader has been carried, in thought, among the various
gaseous elements, that make up atmosphere and oceans, it seems suitable
that we should say farewell to him upon the discussion of that element
that may be called the characteristic material of our solid earth.
INDEX.
Abel, F. A., 182
Acid, Boric, 157
——— Nitric, 35, 168
——— Sulphuric, 35, 37, 152
——— Chlorohydric, 33, 190
——— Phosphoric, 192
Affinity, Chemical, 44, 46-52
Alizarine, 226
Alkali Trade, 94, 106
Allotropism, 190
Amethyst, 229
Ammonia, 166, 174, 225
Anhydride, 151
Anhydrite, 146
Anthracene, 226
Antimony, Sulphide of, 148
Apatite, 188, 189
Arsenic, Sulphide of, 148
Atom, 41, 42
Atomic Theory, 52
Atmosphere, 170
Bacon, Roger, 178
Balard, 100
Balloons, 74
Barilla, 107
Benzole, 227
Berthollet, 94
Berzelius, 24
Beverages, effervescing, 219
Binary Compounds, 32
Biot, 80
Black, Joseph, 61, 63, 76
Bleaching-Powder, 93
Blende, 146
Blowpipe, Compound, 129
Bone-Ash, 187
Borax, 157
Boron, 157
Boussingault, 217
Brandt, 187
Bromine, 100
Carbon, 197
——— Dioxide, 173, 216
——— Monoxide, 215
Cavendish, Henry, 60
Charcoal, 197
Chemistry, Scope of, 7, 9
Chlorine, 85
Cinnabar, 146
Coal, 201
Coal-tar, 226
Coke, 226
Compounds, 32
——— Number of, 8, 9
——— Organic, 221
Copper, Sulphate of, 51
Cotton, 181
Courtois, 108
Current, Galvanic, 64
Daguerre, 103
Dalton, John, 52, 56
Davy, Humphry, 60, 86, 108
De Rozier, 78
Diamond, 203
Diatoms, 185, 228
Diffusion, 69
Döbereiner, 70
Dynamite, 183, 185
Earth’s Crust, Composition of, 15
Elements, Chemical, 9, 12, 14, 28
——— Names and Symbols of, 19, 23
Equivalence, 48, 72
Ethylene, 227
Explosives, 177
Fertilizers, 188
Fluorine, 112
Fireworks, 180
Fulminates, 181
Galena, 146
Gas, 63
—— Illuminating, 221
Gas-Carbon, 226
Gay-Lussac, 80
Glaisher and Coxwell, 81
Glass, 229
Glycerine, 184
Granite, 228
Graphite, 201
Gun-Cotton, 181
Gunpowder, 177
Haüy, 15
Heat, unit of, 71
Hydrogen, 58
Iodine, 105
Iron, Sulphide of, 146
Janssen, 83
Kelp, 107
Lamp-Black, 200
Larderel, 160
Lavoisier, 19, 21, 118
Lead, 34
——— Sulphide of, 146, 148
Leblanc Process, 94
Liebig, 101
Light, Calcium, 131
——— Electric, 211, 226
Limestone, 209
Lithium, 30
Marble, 209
Mass, 39
Matches, 192
Mayow, 121, 163
Metals, 28, 29
——— Names of, 16, 20
Mercury, 30
——— Sulphide of, 146
Moisture in the Air, 173
Molecule, 40
Montgolfier, 74
Murdoch, 222
Nobel, 185
Nitrogen, 162
Nitroglycerine, 184
Nomenclature, Chemical, 19, 20, 32, 33, 37
Non-metal, 30
Oxide, Ferroso-ferric, 66
Oxygen, 117
——— Abundance of in the earth, 14, 16
Palladium, 70
Pelletier, 89
Petroleum, 209
Photography, 93
Phosphorus, 187
Phosphorus Necrosis, 189
Phosphuretted Hydrogen, 191
Potassic Chlorate, 123
Priestley, Joseph, 64, 118, 163
Puymaurin, 115
Pyrites, 146
Quartz, 228
Roe, 89
References, Reading, 10, 17, 24, 27, 31, 38, 45, 56,
73, 84, 98, 111, 116, 133, 156,
161, 186, 196, 214
Rutherford, 163
Scheele, 85, 114, 118, 162, 187
Silicon, 228
——— Abundance of, 16
Sodium, 67
Sugar, 41
Sulphur, 142
——— Dioxide, 33, 149
——— Trioxide, 33, 151
Sulphuretted Hydrogen, 147
Ternary Compounds, 34
Van Helmont, 63
Varech, 107
Vitriol, Oil of, 152
Water, 127, 134
Weight, Atomic, 17
Zinc, 68
—— Sulphide of, 146, 149