Molecular physics

“ But, in the language of physical science, which, by the nature of the case, is materialistic, the actions of men, so far as they are recognisable by science, are the results of molecular changes in the matter of which they are composed; and, in the long run, these must come into the hands of the physicist. A fortiori, the phænomena of biology and of chemistry are, in their ultimate analysis, questions of molecular physics. Indeed, the fact is acknowledged by all chemists and biologists who look beyond their immediate occupations. ”

“ See, then, the contrast. {111} The truths of the Ab­stract-Con­crete Sciences do not imply specific individuality. Neither Molar Physics, nor Molecular Physics, nor Chemistry, concerns itself with this. The laws of motion are expressed without any reference whatever to the sizes or shapes of the moving masses; which may be taken indifferently to be suns or atoms. The relations between contraction and the escape of molecular motion, and between expansion and the absorption of molecular motion, are expressed in their general forms without reference to the kind of matter ”

“ for in almost every branch of molecular physics it may be held, that a hypothetical theory is necessary as a preliminary step to reduce the expression of the phenomena to simplicity and order, before it is possible to make any progress in framing an abstractive theory. ”

“ If one now reflects that a molecule commonly contains, so far as we know, quite a large number of different freely moving constituents, certainly, that a normal molecule of a monatomic gas, e. g., mercury, possesses numerous freely moving electrons, then, in accordance with the law of uniform energy distribution, the intra-molecular energy must constitute a much larger fraction of the whole specific heat of the gas, and therefore must turn out much smaller, than is consistent with the measured values. ”

“ In the same way that, for the purpose of knowing the constitution of matter, it first occurred to us to investigate gases, which appear to be molecular edifices built on a more simple and uniform plan than solids, we ought naturally to think that an examination of the conditions in which emission and absorption are produced by gaseous bodies might be eminently profitable, and might perhaps reveal the mechanism by which the relations between the molecule of the ether and the molecule of matter might be established. ”

“ In the special departments of dynamical physics on the other hand, the molecular theory, there dynamical and therefore much more difficult and less definite, is an indispensable part of the framework of science; and even experimental chemistry now leans more and more on new physical methods and instruments. Without molecular theory the clue which has developed into spectrum analysis, bringing with it stellar chemistry and a new physical astronomy, would not have been available ”

“ In its place there was elaborated, chiefly through the efforts of Laurent and Gerhardt, a conception of the molecule as a unitary structure, built up through the aggregation of various atoms, in accordance with "elective affinities" whose nature is not yet understood A doctrine of "nuclei" and a doctrine of "types" of molecular structure were much exploited, and, like the doctrine of compound radicals, became useful as aids to memory and guides for the analyst, indicating some of the plans of molecular construction, though by no means penetrating the mysteries of chemical affinity. ”

“ The molecule of a given substance, though often called an atom, is a system of primitive elements; and elements acting according to the Newtonian law can give rise to molecular systems which, at very small distances, will act according to any other law that may be indicated by molecular phenomena. This other law depends entirely on the number, kind, strength, and geometrical arrangement of the primitive elements which enter into the constitution of the molecule ”

“ Let the reader observe that this conclusion regards the action of primitive elements, not the action of molecules. That molecular actions at molecular distances are not inversely proportional to the square of the distance is a known fact. Molecular cohesion, for instance, is immensely greater than it could possibly be by the Newtonian law; so also molecular repulsion. This is what prevented physicists from recognizing the applicability of the Newtonian law at molecular distances. ”

“ A number of molecules moving in obedience to dynamical laws will pass through a series of configurations which can be, theoretically determined as soon as the structure of each molecule and the initial position and velocity of every part of it are known. The determination of the series of configurations developing out of given initial conditions is not, however, the problem of the kinetic theory: the object of this theory is to explain the general properties of all gases in terms only of their molecular structure. ”

“ For pith-balls read atoms, and we have an explanation of the univalent atoms like those of chlorine and sodium which act as single poles; and this is confirmed by the fact that such atoms are never found isolated, but are always associated in a molecule with at least one other atom which forms the opposite pole of the molecular system. Bivalent or magnetic atoms, on the other hand, which have two poles, like those of mercury and zinc, may constitute a complete polar system and be found isolated, and form the class of molecules which consist of single atoms. ”

“ Only, the specific power of the slightly complicated molecule H2O cannot possibly afford any standard for the estimation of the specific power of the immensely more complicated molecule constituting protoplasm. Protoplasm differs from water in proportion to its synthetical wealth. Whatever synthetical wealth may be the symbol of, in its gradations is to be sought the source of all difference in Nature. This is the gist of what chemistry teaches: the work of Nature consists in molecular synthesis. It has required the ceaseless toil of endless ages to build up the molecule of living matter. ”

“ Among the several elements concerned, there are wide differences in molecular mobility, and probably in the rates of molecular vibration. Each is combined with one of the others, but is capable of forming various combinations with the rest. And they are severally in presence of a complex compound into which they all enter, and which is ready to assimilate with itself the new compound molecules they form. Certain of the ethereal waves falling on them when thus arranged, cause a detachment of some of the combined atoms and a union of the rest. ”

“ Hence a molecule is nothing but a number of simple elements (some attractive and some repulsive) permanently connected by mutual action in one dynamical system. We say permanently connected; because no system of elements which lacks stability can constitute permanent substances, such as we meet everywhere in nature. Yet the stability of the molecular system is not an absolute, but only a relative, unchangeableness ”

“ While the molecules as wholes increase one another’s oscillations, or derange one another’s oscillations, or both, the components of them cannot be so stably arranged that members of the one group are wholly inoperative on members of the other group. And if they are operative, then there must be a compound form of molecular motion which arises when masses of highly-compounded molecules of unlike kinds, are made to act on one another. ”

“ It is noteworthy, the we are led exactly to the above presupposed changes of dimensions, when we first (without consideration of the molecular motion) assume, that in a rigid body which remains at its own, the forces, attractions or repulsions which act on an arbitrary molecule, are mutually in equilibrium, and second — for which, however, there is no reason — when we apply to these molecular forces the law which we have derived in § 23 for the electrostatic actions. ”

“ Etheric atoms combine to form molecules in many different ways, but combinations involving fewer atoms than the eighteen which give rise to hydrogen, make no impression on the physical senses nor on physical instruments of research. They give rise to varieties of molecular ether, the comprehension of which begins to illuminate realms of natural mystery as yet entirely untrodden by the ordinary physicist. ”

“ We appear to be now fairly embarked in the prosecution of molecular dissection, and our chief guide is the theory of valency, itself a development of the dualistic chemistry.
Each elementary atom, I have said, seems to have the power of directly binding to itself a maximum number of other atoms; but it would further appear as if the groups of atoms thus produced had also a certain binding power, but this more indefinite than the atomic binding power, and very variable under different physical conditions. ”

“ In fact a favourite problem of his is—Given the molecular forces in a mutton chop, deduce Hamlet or Faust therefrom. He is confident that the Physics of the Future will solve this easily. ”

“ It is for the sake of a somewhat commensurate appreciation of vitality, of high-wrought molecular organization, that it is necessary, again and again, to point out the might of potentiality intrinsic to matter, the vast and specific stores of force locked up in the peculiar molecular entanglements which constitute our different substances. ”

“ The study of the way in which atoms combine into molecules belongs to chemistry, and will not much concern us. We are concerned with the structure of atoms, the way in which electrons and nuclei come together to build up the various kinds of atoms. This study belongs to physics almost entirely. There are three methods by which most of our knowledge is obtained: the spectroscope, X-rays, and radio-activity. The hydrogen atom, which has a simple nucleus and only one electron, is studied by means of the spectroscope almost alone. ”

“ As a result of the law of chemical action, that most elementary bodies exist in a condition where two atoms are joined together to form a molecule, it follows, that in most instances the molecular weights of the elements are double their atomic weight. ”

“ One of the most remarkable results of the progress of molecular science is the light it has thrown on the nature of irreversible processes—processes, that is, which always tend towards and never away from a certain limiting state. Thus, if two gases be put into the same vessel, they become mixed, and the mixture tends continually to become more uniform. ”

“ In molecular bodies motions are correlated in a manner yet unknown, but molecules are known to have interior motions exhibited in response to motions in the ether as its particles impinge on ponderable matter. The correlated structural motions of the molecule may be transmuted by collision with ethereal particles and be converted into heat—a mode of motion—so that which is structural motion will appear as heat, and if the transmutation is carried to a sufficient degree the structure of a molecular body will be destroyed, for by heat molecules are reduced to lower molecules or to atoms. ”

“ The process by which the molecules become distributed into distinct species is not one of which we know any instances going on at present, or of which we have as yet been able to form any mental representation. If we suppose that the molecules known to us are built up each of some moderate number of atoms, these atoms being all of them exactly alike, then we may attribute the limited number of molecular species to the limited number of ways in which the primitive atoms may be combined so as to form a permanent system. ”

“ When the nebulous mass has [119] reached a particular stage of condensation—when its internally-situated atoms have approached to within certain distances, have generated a certain amount of heat, and are subject to a certain mutual pressure, combinations may be anticipated. Whether the molecules produced be of kinds such as we know, which is possible, or whether they be of kinds simpler than any we know, which is more probable, matters not to the argument. It suffices that molecular unions, either between atoms of the same kind or between atoms of different kinds, will finally take place. ”

“ We have thus arrived at morphological constants of very considerable importance, which are best termed “Molecular Distance Ratios,” as they express the relative distances apart in the three directions of space of the centres of gravity or other representative points of contiguous chemical molecules. They are dependent on three experimental determinations, atomic weight, specific gravity, and crystal angles, all of which have now been brought to the highest pitch of refinement and accuracy; hence the molecular distance ratios are particularly trustworthy constants. ”

“ In molecular structure, as determined by chemical activity, the molecules and atoms are arranged in definite ways which depend upon the rate of vibrations of the components. The atoms are set in definite positions to constitute a given molecule. But atoms or molecules may cohere for other reasons, gravitative or magnetic, and relative positions would be immaterial. In the absence of temperature, a solid body would be solider and stronger than ever, while a gaseous mass would probably fall by gravity to the floor of the containing vessel like so much dust. ”

“ We have strong reason for assuming that the ultimate particles of matter—the atoms and molecules of which it is made up—are endowed with forces coarsely typified by those here ascribed to the leaves. The phenomena of crystallization lead, of necessity, to this conception of molecular polarity. Under the operation of such forces the molecules of a seed, like our fallen leaves in the first instance, take up positions from which they would never move if undisturbed by an external impulse. ”