ON THE TRANSMUTATION OF MATTER.

T seems strange at first sight, that so many men, not merely

of their time for a philosophical spirit and wide range of learning, should have spent a large part of their lives in the vain attempt to transmute the baser metals into gold. The greatness of the prize played for would no doubt enchant many; and the fancied superiority contained in the possession of some secrets of nature, and the practice of a mysterious art, as well as the real influence which a reputation for greater knowledge and supernatural power gave them with the world at large, may have been the chief motives with such quacks as Paracelsus, but could hardly have had much influence with true philosophers like Thomas Aquinas and Roger Bacon. But more than this, there seems something in the notion that such a transmutation is possible which has always commended itself to the minds of men, for after dying out it has been revived again with singular pertinacity. However, to account for the attention paid to it in the middle ages, it will be enough to note that it is a dictum of Aristotle, that there is one substance of which all material things consist, that the elements are produced by the accession of certain qualities or affections to this, and are capable of transmutation one into another in a circle. The elements spoken of are, of course, the fourearth, air, fire, and water-about which there can be no question now; the former part of the assertion is still open to discussion. Aristotle was not the first to propound that part of his theory; it may be traced back to the earliest Greek philosophers, and has even been supposed to be a relic of a former, more elaborate system, derived from the East. Be that as it may, the Greeks in general despised experiment, and tried to

ส

search out nature only by thinking, so it is no wonder if they left the doctrine on this point much as they found it. Even with Aristotle-albeit the most acute and accurate observer of nature among his countrymen,-perhaps, that ever lived-it was only a pretty conceit, purely speculative, and led to nothing more. With the philosophers of the middle ages, on the other hand, who tried to deduce from it a practical result, if it did not turn out as true as they had hoped, it at least led to the discovery of a multitude of facts, the foundation of the modern science of chemistry; and no one at all acquainted with the wonderful powers of nature thus brought to light will feel surprise at the enthusiasm excited in the pursuit.

:

The question involved herein seems to have acquired fresh interest of late. Some high authorities have given it as their opinion that recent discoveries render probable the theory of one substantive element of matter, and have expressed their hope that the means of effecting the wished-for transmutation may yet be found out. Such queries as the following are often repeated whether it is incredible that arsenic may be developed in the human body as a result of morbid action? and whether the gold of California and Australia may not have grown in recent times by the action of electricity upon the quartz, or other minerals which do not yield it by common modes of reduction? To prove the negative is of course impossible. In such cases it is especially needful to guard against the subtle fallacy of reasoning upon our ignorance, instead of upon that amount of positive knowledge, how slight soever it be, which we are sure of, lest we fall into that kind of error which led a famous philosopher to imagine he had refuted a rival theory by assuming that the particles of an elastic fluid must be globular because no reason appeared to the contrary. The question is no doubt partly a metaphysical one; nevertheless it is not hopeless of solution; the objects of it are at least within our reach, and we are justified in expecting daily to gain something to our knowledge of them. It may be worth while to inquire how far the facts already ascertained will carry us, how far they help to bridge over the gap which separates this question from the region of physics.

It can hardly be necessary to suppose that the substance of matter, if there should be but one, is such a mere peg to which qualities may be appended as Aristotle held,* with extension, indeed, that is length, breadth, and thickness, but no sensible qualities. Rather it may be allowed, as far as the present question is concerned, to possess all those qualities which are alike

*De Gen. et Cor. ii. 1.

Matter and Element defined.

125

in bodies of every kind that are capable of being designated by the common term matter, in the sense in which chemists use that word; for to them it is not a simple object of thought, but something subject to gravity, and the balance gives the measure of its quantity. This definition of matter may be thought an assumption, but it is the foundation of chemical science, which might indeed be defined with reference to it; besides, the question is not now of any change of heavy into weightless things, and is so far limited. The notion of one substance on which weight intrinsically depends has, as far as it goes, the merit of simplicity, which may perhaps be deemed characteristic of truth in natural philosophy; at any rate, it is the wont of nature, by variations on a common type, to produce the most numerous and beautiful adaptations.

In order to make the facts about to be spoken of generally intelligible, it is necessary to premise that, by carefully examining and analyzing everything which has come in their way, chemists have made out about sixty-four different kinds of matter, of some one of which, or of two or more of them united in various proportions according to definite laws, all known bodies are formed. Four of the sixty-four are certainly gaseous at ordinary temperatures, one probably so, two liquid, and the rest solid. They are usually called elements, or simple bodies, because they are deemed the simplest parts of matter, or simple in those ultimate parts, be they atoms or not, in which chemical qualities reside. The reason for this is that they cannot, by the most powerful means of analysis at present known, be resolved into any simpler constituents, nor be formed by the union of such: that is, they have not yet been shown to be compound. They are distinguished from one another by some differences observed in their several properties, either in the separate state or in compounds.

Transmutations of these elements might take place either if some of them should be compounded of others, or if their distinctions should not depend on fixed and essential differences in their substance.

That some of them may hereafter prove to be compound is rendered probable by the past history of chemistry, as well as by the properties observed in some of these bodies themselves. For ages water was considered an element, and, indeed, it is hard to assign any reason why it should not have been so considered, until the time when Cavendish and Watt proved it to be formed by the union of the gaseous elements, now called oxygen and hydrogen. Still longer were the caustic alkalies, potash and soda, deemed simple bodies; until the discovery in the galvanic battery of a more powerful agent of decom

position than any heretofore applied, led to the opposite conclusion, namely, that they are each formed of a metal united with oxygen, and precisely similar in constitution to many oxides previously well known to be compounds. When the varied causes which modify chemical action are taken into account, it appears all the more likely that other discoveries will be made in the same direction. The common effects of heat in promoting chemical action have been long known, as well as those of chemical action in producing heat. A coal must be heated ere it will unite with the oxygen of the air as it does in burning; but the heat developed by that union suffices to maintain the action. Such instances might be brought forward without end, and likewise cases of decomposition, well known from the earliest times; but some results lately observed seem to exhibit the action of heat in a new light, the alternate union and separation of the same two things at different temperatures. At the ordinary temperature of the air, baryta (oxide of barium) and oxygen have no action on each other, but they unite at a low red heat to form binoxide of barium; while at a still higher temperature this is again resolved into the same two constituents. A like action takes place with mercury and oxygen. Oxide of silver, too, is decomposed into metallic silver and oxygen by a high temperature, while at a still higher they reunite; although the compound then formed is not the same as oxide of silver, and is decomposed again as the temperature falls. The effects of electricity, in some respects, exceed those of heat, and their discovery is only of modern date. Those of light, as striking as either of the others, and as important to organic life, have only lately begun to be studied. Photography has brought some facts concerning it to the notice of all; and the action of light on vegetables is familiar enough, though it may not have occurred to every one that the effects are chemical. But they are so. Much of the solid fibre of plants is obtained from the carbonic acid and moisture of the air, absorbed by the leaves, and transformed under the influence of light by a process just the inverse of that which ensues in burning the wood so formed. Many of the other products of healthy plants, such as the green colouring matter of leaves, are not developed in the dark. Even variations of pressure are known to have their effect on chemical action. The most usual cases are those in which they affect the volatilization of some gas; thus limestone, which in an open kiln parts with its carbonic acid at a red heat, may be fused unchanged in a close vessel, where the pressure of a small quantity of the gas at first set free prevents the expansion of the remainder. The state of a

Causes modifying Chemical Action.

127

liquid is in general the most favourable for chemical combination, and this depends directly upon the temperature and pressure; the results, however, are not on a uniformly varying scale, and we must be prepared to expect corresponding variations in chemical action;* as heat does not always expand bodies, so it is now discovered that pressure does not always render them solid; ice is found to liquefy partially under increased pressure, and at the same time its temperature to fall; and a like result would probably ensue with all the many bodies which expand in passing from the fluid to the solid state. But it is not only by affecting the fluidity of bodies that pressure promotes or retards chemical action. Phosphorus placed in a jar of pure oxygen at a temperature of 60° F., under the ordinary pressure of the atmosphere, is not affected, but slow combustion sets in as soon as the pressure is partly removed, or the gas diluted with nitrogen. A similar effect is produced with phosphuretted hydrogen gas, which, if it contain none of the spontaneously inflammable compound, may be introduced at the pneumatic trough into a jar, partly filled with air or oxygen, and no combination take place as long as the pressure is that of the atmosphere; but if the jar be raised, so that the pressure of the gas within is diminished, combination follows with explosion. It is just possible, in such a case, since the state of a liquid is the most favourable for chemical union, and since gases by expansion are, with reason, considered to approach more and more towards the condition of inelastic fluids,† that they may likewise thereby acquire more facility of entering into combination. Be that as it may, the fact is a striking one.

Not less remarkable than any of these is the action which some bodies seem to induce by their presence merely; such as that of finely divided platinum and other metals, silica, alumina, and so on, in promoting the union of gases at temperatures much lower than is otherwise necessary. It is this action of finely divided platinum which inflames the jet of hydrogen in Döbereiner's self-igniting lamp; and by a kind of slow combustion will convert, with a sufficient supply of air, any amount of the vapour of ether, or of spirits of wine, into vinegar. Like effects in decomposition are also produced; as when black oxide of manganese, or of copper, or other things

*It must be borne in mind that the results of chemical action, that is, the compounds produced, never vary by insensible degrees, or pass gradually from one to another, according to circumstances, but are always definite.

Liquids are very nearly inelastic.