III.—CHEMISTRY OF AIR.
CARBONIC DI-OXIDE FROM THE LUNGS PASSED INTO LIME WATER (CAO₂H₂).
Experiment.—Dissolve some quicklime (CaO₂H₂) in water. Let it settle and pour off the clean part. Blow your breath into this. What follows, and why?
A quaint old book called “The Tin Trumpet” remarks that “three bad mothers have borne three good daughters.” Long-Suffering begat Patience, Astrology gave birth to Astronomy, and Chemistry is the daughter of Alchemy. The facts of science have taken the place of the fancies of the early investigators. Men used to be attacked, when they entered ravines and caverns, by supernatural beings, as they supposed, who choked, and sometimes killed them. In 1754 Joseph Black showed that these fatal results were due alone to the presence of an invisible gas, which he called “fixed air,” as he found it locked up in limestone. “Geist,” the name invented by Van Helmont to represent this strange power, signified ghost or spirit, so that the “ghosts” of the seventeenth century are the gases of the nineteenth. The word gas is derived from geist.
In studying the history of science we often wonder at the near approach which men made to truths which remained undiscovered for a long time after. One finds, all along, intimations of approaching disclosures which resemble those peculiarities in animals and plants that the geologist notes in the lower strata of the rocks, as prophesying the development of future species. The astrologer failed in his attempt to read human destiny, but he led men forward to the time when, in the stars, they should read the “thoughts of God.” The alchemist did not succeed in distilling the “elixir of life,” but he prepared the way for chemists to make those useful discoveries which have greatly promoted the safety and comfort of men and extended the period of human life. Some of the most important investigations in which science is now engaged concern the character and contents of that all-pervading aërial ocean which surrounds our earth to the height of from fifty to five hundred miles. Pure air is one of the great essentials of health and life. How to secure it is a difficult but beneficent inquiry which the spectroscope, microscope and chemical analysis may yet answer.
NITRIC ACID DISSOLVING COPPER.
Experiment.—Place copper in nitric acid. Also try iron and zinc successively.