Part 13

It has also the power of combining with and destroying all noxious smells, and is invaluable as a purifier of foul rooms, and destroyer of infection. For these latter purposes it is used in combination with lime, either in substance or solution, under the name of “Chloride of Lime.”

Chlorine gas is a powerful supporter of combustion, many of the metals taking fire spontaneously when introduced in a fine state of division into the gas.

Experiments.

1. Into a jar of chlorine gas introduce a few sheets of copper leaf, sold under the name of Dutch foil, when it will burn with a dull red light.

2. If some metallic antimony in a state of powder be poured into a jar of this gas, it will take fire as it falls, and burn with a bright white light.

3. A small piece of the metal potassium may be introduced, and will also take fire.

4. A piece of phosphorus will also generally take fire spontaneously when introduced into this gas. In all these cases direct compounds of the substances with chlorine are produced, called chlorides.

5. If a lighted taper be plunged quickly into the gas, it will continue to burn with a dull light, giving off a very large quantity of smoke, being in fact the carbon of the wax taper, with which the chlorine does not unite; while the other constituent of the taper, the hydrogen, forms muriatic acid by union with the chlorine.

6. This substance has the property of destroying most vegetable colors and is used in large quantities for bleaching calico, linen, and the rags of which paper is made. It is a curious fact that it shows this property only when water is present, for if a piece of colored cloth is introduced dry into a jar of the gas, also dry, no effect will be produced--wet the cloth, and reintroduce it, and in a very short time its color will be discharged.

7. Introduce a quantity of the infusion of the common red cabbage, which is of a beautiful blue color, into a jar of this gas, and it will instantly become nearly as pale as water, retaining a slight tinge of yellow. A solution of sulphate of indigo can always be obtained, and answers well for this experiment.

Muriatic Acid Gas, or Chloride.

With chlorine, hydrogen forms a compound called muriatic, or hydrochloric acid gas. It cannot easily be formed by the direct union of its elements, but is procured from some compound in which it exists ready formed. Common salt (chloride of sodium) is generally employed; and when acted on by strong sulphuric acid (or oil of vitriol), the gas is disengaged in abundance. It must be collected over mercury, for water absorbs it, forming the liquid muriatic, or hydrochloric acid.

A lighted taper plunged into this gas is instantly extinguished. It is very dangerous to animal life if respired. It has the property of destroying animal effluvia, and was once employed to purify the cathedral of Dijon, which was so filled with putrid emanations from the bodies buried in it, that it had been closed for some time. It perfectly succeeded, but it is so destructive to all metallic substances that it is not used now, for the chlorides of lime and zinc have since been discovered to act more effectually than the muriatic acid gas, without its inconvenience.

The compounds of hydrogen with iodine are passed over.

With nitrogen, hydrogen unites and forms one of the most extraordinary compounds in the whole range of chemistry,--the gas called ammonia. This is the only gas possessing what are called alkaline properties; i.e., it changes the blue color of certain vegetables to green, yellow to deep brown, and unites with the acids to form neutral compounds, just as the other alkalies, potash and soda, which are oxides of metals. It may be procured in abundance by heating the hydrochlorate of ammonia, or sal ammoniac, as it is usually called, with quick-lime, which takes the hydrochloric acid, and sets free this remarkable gas. It must be received over mercury, as it is absorbed to almost any extent by water, forming the fluid sold as “spirits of hartshorn” in the shops.

This gas is colorless and transparent, lighter than atmospheric air, and will not support combustion; it has a very pungent but not disagreeable smell. Under certain circumstances it is combustible.

Experiments.

1. Take a bottle containing chlorine gas, and invert over its mouth another filled with ammoniacal gas; then if the bottles be held in the hand (guarded by a pair of gloves), and suddenly turned, so that the chlorine be uppermost, the two gases will unite so rapidly that a white flame fills the bottles for an instant.

2. Substitute for the chlorine of the last experiment a bottle of carbonic or hydrochloric acid gas; in either case the gases disappear, and a light white powder settles on the sides of the bottles, being the carbonate or hydrochlorate of ammonia, according to the acid used.

Carbonate of ammonia is the substance sold for “smelling salts;” and the hydrochlorate, or muriate of ammonia, is the salt called “sal ammoniac,” whence the alkaline gas was first obtained, and from which it got its name of ammonia. The salt itself was so called, because it was formerly brought from the deserts near the ruins of the temple of Jupiter Ammon.

This salt is, as has been shown, a compound of muriatic acid gas and ammoniacal gas, containing therefore only three simple elements--hydrogen, chlorine, and nitrogen, all gases, and known only in the gaseous state, its symbol being NH{4}C{2}; yet they by union form a solid body, resembling in all essential qualities the salts of potash and soda, which are oxides of known metals. Moreover, if some mercury be placed in a solution of this salt, and subjected to the action of galvanism, the negative pole being applied to the mercury, and the positive to the sal ammoniac, the mercury presently loses its fluidity, increases greatly in size, and in fact presents the same appearance as when it is mixed with some metal, forming what is called an “amalgam.” When the battery ceases to act, a succession of white films forms on the surface of the amalgam, and the mercury soon returns to its original state. How is this to be explained? Some chemists have supposed that there must be a base united to the mercury, and have named this hypothetical substance “ammonium,” to correspond to potassium and sodium, the bases of potash and soda, which resemble ammonia in so many properties. But what is this ammonium? and how is it formed? for hydrogen and nitrogen are simply elementary bodies. Are all metals compounds of gases? and are there but a few elements instead of the 64 now enumerated? This, however, is a difficult question, not fitted for discussion here.

Carbonate of ammonia may be obtained by mixing together powdered chalk (which is a carbonate of lime) and muriate of ammonia, and heating the mixture in close vessels, when the salt in question will rise in fumes, and be condensed in a mass in the upper part of the vessel. It is, however, so largely produced in other manufactures, particularly in gas-works, that there is no necessity to resort to the more expensive and direct method. It is the well-known “smelling salts.”

The only other salt of ammonia worth our notice here is the nitrate, from the destructive distillation of which is obtained the nitrous oxide, or laughing gas, already mentioned.

Iodine--Bromine--Fluorine.

On the coasts of certain islands belonging to the Duke of Argyll, vast quantities of sea-weed are occasionally torn up from their ocean beds and deposited on the shores. This weed, after being partially dried by exposure to the sun and air, is burnt in a shallow pit; the ashes are then collected, and form the commercial raw material called kelp, from which iodine is procured by a gradual series of processes.

Experiments.

Iodine has a beautiful metallic luster, with a bluish black color, and should be kept in a well-stoppered bottle. A small quantity placed in a clear flask and heated, affords a magnificent violet vapor, which may be poured from the flask into another glass vessel, when it condenses again into crystalline plates. The color of the vapor originates the name of this element, so called from a Greek word, meaning violet-colored. If a little iodine be placed in contact with a thin slice of phosphorus, the latter takes fire almost immediately.

Bromine.