There are four kings among chemical substances: Oxygen, king of all the
elements; gold, king of the metals; oil of vitriol, king of the acids,
and potash, king of the bases.
[Illustration: PREPARATION OF OXYGEN FROM MERCURIC OXIDE—MATERIALS USED
BY DR. PRIESTLY.]
This term of distinction is given to oxygen because of its marvellous
activity and range of powers; it unites with all elements save one,
fluorine. Its grasping disposition is often resisted by man; he keeps it
from destroying his house by painting it; from gnawing at the quivering
nerves of his teeth by filling them; from devouring his fruits by canning
them; and Monsieur Goffart has now taught us to save green food for our
cattle, from its ravages by excluding O from our silos. In spite of its
destroying power we can not live without it. The light and warmth in our
homes are produced by its rapid union with fuel. Every moment we breathe
we are absorbing it into our bodies, where it unites with waste matter,
producing heat and energy, and removing that which would clog and poison
the system. There is nothing in nature more beautiful than the plan by
which the animal and vegetable kingdoms mutually sustain each other by
the interchange of O. Look at this little aquarium; here are two or three
shiners, some goldfish, and a few water plants. In this little world
we may see exactly what goes on in the great world. That goldfish is
inhaling O, which is conveyed into the capillaries, unites there with
the carbon, forming CO₂, which is exhaled, seized upon by the plant, and
in the wonderful laboratory of its cells, the C is separated from the
poisonous gas, and retained, while the O is thrown off, again to be used
by the fish. Upon the nice adjustment of the plants to the animals, and
vice versa, depends the life of both. While upon this subject we might
note another interesting evidence of beneficent design in the provision
made for both fish and plants.
Water absorbs gases with great readiness—some of them it takes more
readily than others; for example, a pint of water will absorb seven
hundred pints of ammonia gas. It will take but its own volume of carbonic
anhydride under one pressure of the atmosphere.
The descending rain drops absorb these two gases and convey them to the
rootlets of the plant, for food. More wonderful still, the Almighty has
arranged that water should remove O from the air more readily than it
does nitrogen; consequently the rain carries down the O to the fish in
river, lake and ocean, adding its life-giving principle to the air, which
is always contained in water. It is a pretty sight to watch the breathing
of a fish as he sends the rapid currents of water through his gills in
the act of aërating the blood, which, as it passes through, gives them a
crimson color.
It may easily be proved that plants throw off O, by submerging any
vigorous growing plant in a jar of water; in a short time little bubbles
will be seen clinging to the leaves; now fill a bottle with water,
invert, and touch the little globules gently, when they will detach
themselves and pass up into the bottle, displacing the water, and may
afterward be used in experimentation. Perhaps some of you, while drinking
at the brook, have noted these bubbles of O on the leaves of the graceful
water plants below. This is the only place in nature where you can see O
free, and indeed you do not see it here, for O is a colorless, tasteless,
odorless substance; what you do see is the thin sphere of water which
contains it.
O is held by many substances so tenaciously that we can not liberate
it; this gives us “terra firma.” Sand, and many rocks consist of O and
silicon, but the greatest heat and heaviest blows can not separate them.
There are materials, however, which readily yield their O. Dr. Priestly
first found it by heating with a burning glass a compound known now as
red oxide of mercury. The O went off, leaving the shining quicksilver.
You may repeat this historic experiment by placing the material in a test
tube and heating it over an alcohol lamp.
Another substance used for this purpose is black oxide of manganese
(MnO₂), but that which is now generally employed is a white salt, kept by
every druggist, and usually called chlorate of potash (HClO₃).
[Illustration: PREPARATION OF OXYGEN FROM A MIXTURE OF POTASSIC CHLORATE
(CHLORATE OF POTASH) AND MANGANESE DI-OXIDE.]
Place a small amount of this, mixed with an equal quantity of the
manganese, in a test tube, or flask, and heat over a flame. The O will
be liberated, and may be bottled for use. A strange thing about this
operation is that the MnO₂ yields none of the O, but comes out of the
flask just as it went in. Such action, by mere presence, is called
catalysis. We can not explain it, but have some such phenomena in social
life, perhaps, when two people with an affinity for each other are having
a delightful, confidential chat, and a third person joins the group,
immediately producing silence—a plain case of catalysis! Having secured
several jars of O we are now ready to test some of its interesting
properties. Extinguish a candle and suddenly plunge it into a jar of O.
It is relighted. A better way is to make a taper of waxed thread. This
will keep the live coal better, and may be relighted many times. Attach
to a wire a piece of charcoal bark. Ignite and place in another jar.
Beautiful scintillations fill the jar, star like in form. Take a watch
spring, heat one end and bend. Split a match and attach to the spring,
light and place in the jar. It burns with great brilliancy.
Whittle out a little cup of chalk, or crayon, and place phosphorus in it.
Touch the P with a hot wire and lower the cup, with a wire, into a jar of
O. A beautiful combustion follows. In like manner sulphur may be burned,
and produces a bright blue light.
[Illustration: A TAPER OR CANDLE BURNING IN OXYGEN.]
A little ingenuity will supply all apparatus needed for these and other
experiments with H and O. For example, a common pail with a wooden shelf
in it two or three inches from the top makes an excellent pneumatic
trough for transferring or gathering gases, and if the shelf can not be
procured, two or three bricks in the pail will serve the purpose.
Before dismissing our glass of water we must remark that no matter where
it may be found, in the depths of the sea or on the mountain; as a dew
drop, or sparkling as spray; in lake Nyanza, or lake Chautauqua, the
chemical constituents of water are just the same. Almighty care and
wisdom weighs the atoms, even as “he weighs the mountains in scales and
the hills in a balance.” The _apparent_ character of water, as to color,
form, hardness, saltness, and so on, is often varied by _mixing_ with it
other substances, but the changes produced are not chemical, and belong
more properly to the domain of physics.
NOTE.—The illustrations in this article are from “The Young
Chemist” of Prof. John Howard Appleton. We can heartily recommend
to the members of the C. L. S. C., all of Prof. Appleton’s
admirable works on Chemistry.