_Common Names_ _Chemical Names and Formulæ_
Alum Sulphate of Aluminum and Potassium
Aqua Fortis Nitric Acid, HNO₃
Aqua Regia Nitro-Hydrochloric Acid
Calomel Mercurous Chloride, Hg₂Cl₂
Carbolic Acid Phenol, C₆H₅OH
Caustic Potash Potassium Hydrate, KOH
Caustic Soda Sodium Hydrate, NaOH
Chalk Calcium Carbonate, CaCO₃
Copperas Sulphate of Iron
Corrosive Sublimate Mercuric Chloride, HgCl₂
Cream of Tartar Potassium Bitartrate
Epsom Salts Magnesium Sulphate
Ether Diethyl Oxide, (C₂H₅)₂O
Fire Damp Light Carburetted Hydrogen
Galena Lead Sulphide, PbS
Glauber’s Salt Sodium Sulphate
Glucose of Grape Sugar Dextrose, C₆H₁₂O₆
Goulard Water Basic Acetate of Lead
Iron Pyrites Iron Di-Sulphide, FeS₂
Jewelers’ Putty Oxide of Tin
Laughing Gas Nitrous Oxide, N₂O
Lime Calcium Oxide, CaO
Lunar Caustic Silver Nitrate, AgNO₃
Mosaic Gold Bi-Sulphide of Tin
Muriatic Acid Hydrochloric Acid, HCl
Olefiant Gas Ethylene, C₂H₄
Plaster of Paris Calcium Sulphate
Quartz Silicon Dioxide, SiO₂
Realgar Arsenic Di-Sulphide, As₂S₂
Red Lead Oxide of Lead, Pb₃O₄
Rochelle Salt Sodium Potassium Tartrate
Salammoniac Ammonium Chloride
Salt, Common Sodium Chloride, NaCl
Salt of Tartar Potassium Carbonate
Saltpeter Potassium Nitrate, KNO₃
Salts of Lemon Oxalic Acid
Slaked Lime Calcium Hydrate
Soda Sodium Carbonate
Spelter Zinc
Spirits of Hartshorn Amm. Hydroxide, NH₄OH
Spirits of Salt Hydrochloric Acid, HCl
Sugar of Lead Lead Acetate
Tartar Emetic Potass. Antimony Tartrate
Verdigris Basic Copper Acetate
Vermilion Sulphide of Mercury
Vinegar Dilute Acetic Acid
Vitriol, Blue Copper Sulphate
Vitriol, Green Ferrous Sulphate
Vitriol, Oil of Sulphuric Acid, H₂SO₄
Vitriol, White Zinc Sulphate
Volatile Alkali Ammonia
_What is meant by radio-activity and radio-active substances?_
_Radio-activity_ is the phenomenon associated with substances which
spontaneously emit rays of unique penetrating power through the escape
of electrons and their striking against other substances. Chief of the
radio-active substances are radium, polonium, actinium, thorium, etc.
_What is the history of these substances?_
Henri Becquerel in 1896 first observed this in the case of potassium
uranyl sulphate, the rays from which he found affected a photographic
plate through black paper, thin plates of metal, etc.; the property was
further traced in other uranium salts and in uranium itself. These rays
are known as _Becquerel rays_, and have the further power to render air
a conductor of electricity, and thus to discharge any electrified
substance placed near them.
A charged electroscope forms a test of radioactivity, and the rate at
which the leaves fall measures the degree. Different uranium salts have
different degrees of radio-activity; some varieties of pitchblende, as
also chalcolite, show the property in excess of uranium contained.
Madame Curie, by using the activity test for every precipitate obtained
from pitchblende, succeeded in discovering the elements _polonium_ and
_radium_ in 1898. The next year Debierne discovered _actinium_, another
radio-active element in the same substance. Meanwhile Schmidt and Madame
Curie independently found that the same properties were associated with
_thorium_, its compounds and the minerals containing it. In 1903 Ramsay
and Soddy discovered that radium continuously produces helium, the
lightest of the inactive gases discovered by Ramsay in 1896.
Twenty-eight elements are now classed in three divisions with the three
parents, uranium, thorium, and actinium. Potassium and rubidium have
been shown to be radio-active, but otherwise the alkaline metals do not
enter the classes.
_Describe radium and its special properties._
WHAT IT IS LIKE.--To the eye a tiny sample of radium--or, to speak more
correctly, of one of the radium salts, for radium in a pure state
(_i.e._ the metal) has not been obtained as yet--presents no very
striking appearance. All one sees is a few tiny crystals, or perhaps a
few specks of whitish-looking powder, glowing in the dark with a faint
phosphorescent light similar to that sometimes emitted by a piece of
decaying fish.
THE RADIATIONS are of three kinds, comparable with those of the vacuum
tube: _Alpha_-rays are heavy particles, positively charged, similar to
the canal rays; _Beta_-electrons, negative like cathode rays;
_Gamma_-rays resemble Röntgen rays. They penetrate matter to different
degrees, behave differently under the action of a magnetic field, but
under ordinary circumstances travel in straight lines.
But rays from different elements vary in penetration, and also with the
absorbing substance, varying roughly with the density.
The _Alpha_-rays have a velocity of from 1.56 × 10₉ centimeters per
second (radium) to 2.25 × 10₉ centimeters per second (thorium); they are
particles of helium carrying a double charge of electricity. _Beta_-rays
have a greater range of velocity and approach that of light. Both
_Alpha_- and _Beta_-rays are absorbed by a thickness of one centimeter
of lead, but _Gamma_-rays pass through an inch of lead; they carry no
charge of electricity, yet ionize the air and discharge the
electrometer.
All the rays on impinging on solid particles give rise to _secondary
rays_, sometimes called _Delta_-rays, electrons moving with
comparatively low velocity. The _Alpha_-rays possess ninety-five per
cent of the energy evolved and produce brilliant fluorescence in zinc
sulphide, diamond, etc., the other rays producing this best in willemite
and the platino-cyanides; all become absorbed and transmuted into heat.
Radium every hour generates sufficient heat to raise its own weight of
water from freezing to boiling point.
THE SPINTHARISCOPE.--This is a simple piece of apparatus invented by Sir
William Crookes, by means of which some of the effects of the
_Alpha_-ray particles can be observed in a very striking manner. It
consists of a little screen covered with powdered zinc sulphide. A small
fragment of radium is placed directly in front of the middle of the
screen and in close proximity to it. On observing this screen in the
dark through a suitable lens, scintillating little points of light are
seen to be continually flashing into view and dying away. Each tiny
spark is thought to be produced by the impact of a single _Alpha_-ray
particle. That these particles or emanations must be matter in a state
of extreme attenuation is proved by an experiment of Professor Curie’s
in which a box constructed of platinum was pierced with two holes so
minute as to be capable of retaining a vacuum, and yet these radium
emanations passed through quite freely.
_What are the medical uses of radium?_
Ulcerous growths, birth-marks, and scars are beneficially treated, but
so far the selective action of radium on tissue has not been determined,
nor its bactericidal effect. Its results in the treatment of cancer have
not yet reached a definite stage, though it has been widely heralded as
a specific for that dreadful malady.
The application of the rays is by various methods: inhalation of the
emanation; external application or injection of the emanation condensed
on glycerine, vaseline, oil, water, etc.; or the taking of quinine,
arsenic, bismuth, etc., on which the emanation has been condensed.
Injections of very dilute solutions of radium salts, or insoluble salts
suspended in water, are made. But external applications of the rays are
considered most important; copper plates or linen are coated with
varnish containing the salts, or glass tubes contain them, and the
radiations are directly applied, the surrounding parts being protected
with lead foil.
[Illustration: GAS METER INDICATOR DIALS.]