DECOMPOSITION OF WATER.—Take a grain of potassium, wrap it up in a small piece of thin paper, and introduce it into a test tube, or small phial, inverted under water, and full of the same fluid. It immediately rises to the top, and, combining with the oxygen of the water, an equivalent of hydrogen gas is given off, which expels the water from the tube or phial, and occupies its place. A lighted match brought to the mouth of the tube will prove the presence of the hydrogen.
THE ILLUMINATOR AND EXTINGUISHER.—Take three glass jars, of equal heights, the first containing common air, the second carbonic acid gas, and the third oxygen gas; plunge, successively, a lighted candle into these jars, first into that holding common air, then into the carbonic acid, and, lastly, into the oxygen gas. In the jar containing atmospheric air, the candle will burn with ordinary brightness; in that filled with carbonic acid gas, the flame will be instantly extinguished, but the glowing wick will be relighted in the oxygen, and burn with increased brilliancy.
MINERAL CHAMELEON.—If one part of the oxide of manganese, and three parts of the nitrate of potass, be heated to redness in a crucible till no more oxygen gas be given off (the heat must be very considerable), a friable green powder is obtained, generally known by the name of mineral chameleon, from its property of changing color during its solution in water. If a small quantity of the powder be put into a glass of water, it soon forms a green solution, when it passes into a violet hue; and lastly it becomes of a beautiful red color. If put into warm water, the changes take place more rapidly, and are much more diversified. Mineral chameleon is a manganate of potass, and it rapidly absorbs oxygen from the atmosphere. The changes of color that occur are owing to the different degrees of oxidizement of the metal.
