The Poetry of Science; or, Studies of the Physical Phenomena of Nature

by Robert Hunt

The atmosphere, and these chemically active compounds, contain the same elements, but their mode of combining is different; and what is, in the one case, poisonous to the highest degree, is, in the other, rendered salubrious, and essential to all organized beings.

Nitrogen gas may be regarded in the light of a diluent to the oxygen. In its pure state it is only characterised by its negative properties. It will not burn, or act as a supporter of combustion. Animals speedily perish if confined in it; but they die rather through the absence of oxygen than from any poisonous property of this gas. Yet, in combination, we find nitrogen exhibiting powers of a most energetic character. In addition to the fulminating compounds and the explosive substances already named, which are among the most remarkable instances of unstable affinity with which we are acquainted, we have also the well-known pungent body, ammonia. From the analogous nature of this volatile compound, and the fixed alkalies soda and potash, it was inferred that it must, like them, be an oxide of a metallic base. Davy exposed ammonia to the action of potassium, and to the influence of the voltaic arc produced from 2,000 double plates, without at all changing its character. From its slight tendency to combination, and from its being found abundantly in the organs of animals feeding on substances that do not contain it, it is, however, probably a compound body. A phenomenon of an obscure and mysterious character is presented in the formation of the “ammoniacal amalgam,” as it is called.

Mercury, being mixed with an ammoniacal salt, is exposed to powerful galvanic action; and a compound, maintaining its metallic appearance, but of considerable lightness and very porous, presents itself.[229] This preparation has been carefully examined by Davy, Berzelius, and others. It is always resolved into ammonia and mercury; and, although the latter chemist is strongly inclined to regard it as affording evidence of the compound nature of nitrogen,—and he has, indeed, proposed the name nitricum for its hypothetical base,—yet, to the present time, we have no satisfactory explanation of this apparent metallization of ammonia.

No attempt will be made to describe the various elementary substances which come under the class of metallic bodies, much less to enumerate their combinations. Many of the metals, as silver and copper, are found sometimes in a native state, or nearly pure; but, for the most part, they exist, in nature, in combination with oxygen or sulphur; gold furnishing a remarkable exception. They are occasionally found combined with other bodies,—as oxidized carbon, phosphorus, chlorine, &c.; but these cases are by no means so common. Those substances called metals are generally found embedded in the rocks, or deposited in fissures formed through them; but it is one of the great discoveries of modern science, that those rocks themselves are metallic oxides. With metals we generally associate the idea of great density; but potassium and sodium, the metallic bases of potash and soda, are lighter than water, and they consequently float upon that fluid. We learn, therefore, from the researches of science, that the crust of this earth is composed entirely of metals, combined with gaseous elements; and there is reason for believing that one, or perhaps two, of the gases we have already named are also of a metallic character. Strange as it may appear, there is nothing, as will be seen on attentive consideration, irrational in this idea. Many of the metals proper, under the influence of such heat as we can, by artificial means, command, are dissipated in vapour, and may be maintained in this state perfectly invisible. Indeed, the transparent space above the surface of the mercury in the tube of a barometer, known as the Torricellian vacuum, is filled with the vapour of mercury. There is, therefore, no reason why nitrogen, or even hydrogen, should not be metallic molecules kept by the force of the repulsive powers of heat, or some other influence, at a great distance from each other. The peculiar manner in which nitrogen unites with mercury, and the property which hydrogen possesses of combining with antimony, zinc, arsenic, potassium, sodium, and possibly other metals, besides its union with sulphur and carbon—in all which cases there is no such change of character as occurs when they combine with oxygen—appear to indicate bodies which, chemically, are not very dissimilar to those metals themselves, although, physically, they have not the most remote resemblance.

“We know nothing,” says Davy, “of the true elements belonging to nature; but, so far as we can reason from the relations of the properties of matter, hydrogen is the substance which approaches nearest to what the elements may be supposed to be. It has energetic powers of combination, its parts are highly repulsive as to each other, and attractive of the particles of other matter; it enters into combination in a quantity very much smaller than any other substance, and in this respect it is approached by no known body.”[230]

Many of the elements are common to the three kingdoms of nature: most of those found in one condition of organization are discovered in another. The carbonates are an abundant mineral class. In the vegetable kingdom we find carbon combining with oxygen, hydrogen, and nitrogen: these elements, also, constitute the substance of animals, the proportion of nitrogen being, however, much larger. If one element, more than another, belongs especially to the animal economy, it is phosphorus, although this is not wanting in the vegetable world; and it is not uncommon in the mineral. Sulphur is common to the three kingdoms: it is abundant in the mineral, being one of the products of volcanic action; it is united with the metals, forming sulphurets; and is found in our rocks in the state of sulphuric acid or oxidized vapour, combined with the metallic bases of lime and other earths. In the vegetable kingdom we discover sulphur in all plants of the onion kind, in the mustard, and some others; it enters into the composition of vegetable albumen, and appears always combined with albumen, fibrine, and caseine, in the animal economy.

Chlorine is found most abundantly in combination with sodium, as common salt: in this state, in particular, we may trace it from the depths of the earth, its waters, and its rocks, to the plants and animals of the surface. Iodine is most abundant in marine plants; but it has been found in the mineral world, traced to plants, and it is indicated in the flesh of some animals. Bromine is known to us as a product of certain saline waters, and a few specimens of natural bromide of silver have been examined. Fluorine, the base of the acid which, combining with lime, forms fluor-spar, is found to exist to some considerable extent in bones; it has been discovered in milk and blood; and investigations have proved its existence in the vegetable world. It must not be forgotten that the earths, lime and magnesia, enter into the composition of the more solid parts of plants and animals. Lime is one of the principal constituents of animal bone and shells, and it is found in nearly all vegetables.

Silica, or the earth of flints, is met with in beautiful transparent crystals, in the depths of the mine; in all rock and soils we find it. In the bark of many plants, particularly the grasses, it is discovered, forming the hard supporting cuticle of the stalk, in wheat, the Dutch rush, the sugar-cane, the bamboo, and many other plants.

It is thus that we find the same elementary principle presenting itself in every form of matter, under the most Protean shapes. Numerous phenomena of even a more striking character than those selected, are exhibited in every department of chemistry; but within the limits of this essay it is impracticable to speak of any beyond those which directly explain natural phenomena.