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 NH4C2; 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.
From the Greek, signifies a bad odor, and is most intimately allied with chlorine and iodine; like these elements, it belongs to the sea, and is a constituent of sea-water. Bromine is a very heavy fluid, and should be preserved by keeping it covered with water in a stoppered bottle.
Experiments with liquid bromine are not recommended, as all the most interesting ones can be performed with the vapor, which is easily procured by letting fall a few drops of bromine into a warm dry bottle.