QUERIES SUGGESTED BY THE NEW GASES
Suppose that a few years ago you had asked some chemist, "What are the constituents of the atmosphere?" He would have responded, with entire confidence, "Oxygen and nitrogen chiefly, with a certain amount of water-vapor and of carbonic-acid gas and a trace of ammonia." If questioned as to the chief properties of these constituents, he would have replied, with equal facility, that these are among the most important elements; that oxygen might almost be said to be the life-giving principle, inasmuch as no air-breathing creature could get along without it for many moments together; and that nitrogen is equally important to the organism, though in a different way, inasmuch as it is not taken up through the lungs. As to the water-vapor, that, of course, is a compound of oxygen and hydrogen, and no one need be told of its importance, as every one knows that water makes up the chief bulk of protoplasm; carbonic-acid gas is also a compound of oxygen, the other element this time being carbon, and it plays a quite different rôle in the economy of the living organism, inasmuch as it is produced by the breaking down of tissues, and must be constantly exhaled from the lungs to prevent the poisoning of the organism by its accumulation; while ammonia, which exists only in infinitesimal quantities in the air, is a compound of nitrogen and hydrogen, introducing, therefore, no new element.
If one studies somewhat attentively the relation which these elements composing the atmosphere bear to the living organism he cannot fail to be struck with it; and it would seem a safe inductive reasoning from the stand-point of the evolutionist that the constituents of the atmosphere have come to be all-essential to the living organism, precisely because all their components are universally present. But, on the other hand, if we consider the matter in the light of these researches regarding the new gases, it becomes clear that perhaps the last word has not been said on this subject; for here are four or five other elementary substances which, if far less abundant than oxygen and nitrogen, are no less widely distributed and universally present in the atmosphere, yet no one of which apparently takes any chemical share whatever in ministering to the needs of the living organism. This surely is an enigma.
Taking another point of view, let us try to imagine the real status of these new gases of the air. We think of argon as connected with nitrogen because in isolation experiments it remains after the oxygen has been exhausted, but in point of fact there is no such connection between argon and nitrogen in nature. The argon atom is just as closely in contact with the oxygen in the atmosphere as with the nitrogen; it simply repels each indiscriminately. But consider a little further; the argon atom not only repels all advance on the part of oxygen and nitrogen, but it equally holds itself aloof from its own particular kindred atoms. The oxygen or nitrogen atom never rests until it has sought out a fellow, but the argon atom declines all fellowship. When the chemist has played his tricks upon it, it finds itself crowded together with other atoms of the same kind; but lift up the little test-tube and these scurry off from one another in every direction, each losing its fellows forever as quickly as possible.
As one ponders this one is almost disposed to suggest that the atom of argon (or of krypton, helium, neon, or zenon, for the same thing applies to each and all of these) seems the most perfect thing known to us in the world, for it needs no companionship, it is self-sufficing. There is something sublime about this magnificient isolation, this splendid self-reliance, this undaunted and undauntable self-sufficiency—these are traits which the world is wont to ascribe to beings more than mortal. But let us pause lest we push too far into the old, discredited territory of metaphysics.
PROFESSOR J. J. THOMPSON AND THE NATURE OP ELECTRICITY
Many fascinating questions suggest themselves in connection with these strange, new elements—new, of course, only in the sense of human knowledge—which all these centuries have been about us, yet which have managed until now to keep themselves as invisible and as intangible as spirits. Have these celibate atoms remained thus always isolated, taking no part in world-building? Are they destined throughout the sweep of time to keep up this celibate existence? And why do these elements alone refuse all fellowship, while the atoms of all the other seventy-odd known elements seek out mates under proper conditions with unvarying avidity?
It is perhaps not possible fully to answer these questions as yet, but recent studies in somewhat divergent fields give us suggestive clews to some of them. I refer in particular to the studies in reference to the passage of electricity through liquids and gases and to the observations on radioactivity. The most conspicuous worker in the field of electricity is Professor J. J. Thompson, who for many years has had charge of the Cavendish laboratory at Cambridge. In briefly reviewing certain phases of his work we shall find ourselves brought into contact with some of the same problems raised by workers in the other fields of physics, and shall secure some very interesting bits of testimony as to the solution of questions already outlined.
The line of observation which has led to the most striking results has to do, as already suggested, with the conduction of electricity through liquids and gases. It has long been known that many liquids conduct electricity with relative facility. More recently it has been observed that a charge of electricity carried by any liquid bears a curious relation to the atomic composition of that liquid. If the atom in question is one of the sort that can combine with only a single other atom (that is to say, a monovalent atom), each atom conveys a unit charge, which is spoken of as an ion of electricity. But if a divalent atom is in question the charge carried is double, and, similarly, a trivalent atom carries a triple charge. As there are no intermediate charges it is obvious that here a very close relation is suggested between electrical units and the atomic units of matter.
This, however, is only a beginning. Far more interesting are the results obtained by the study of gases in their relation to the conduction of electricity. As is well known, gases under ordinary conditions are nonconductors. But there are various ways in which a gas may be changed so as to become a conductor; for example, by contact with incandescent metals or with flame, or by treating with ultra-violet light, with Rôntgen rays, or with the rays of a radio-active substance. Now the all-important question is as to just what change has taken place in the gas so treated to make it a conductor of electricity. I cannot go into details here as to the studies that have been addressed to the answer of this question, but I will briefly epitomize what, for our present purpose, are the important results. First and foremost of these is the fact that a gas thus rendered conductive contains particles that can be filtered out of it by passing the gas through wool or through water. These particles are the actual agents of conduction of electricity, since the gas when filtered ceases to be conductive. But there is another way in which the particles may be removed—namely, by action of electricity itself. If the gas be caused to pass between two metal plates, one of them insulated and attached to an electrometer, a charge of positive electricity at high potential sent through the other plate will drive part of the particles against the insulated plate. This proves that the particles in question are positively electrified. The amount of the charge which they carry may be measured by the electrometer.