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Even to-day and among our own friends are to be found men who fail to see that the university that we know not only watches with some care over teaching schedules so that the man who wishes to follow productive lines in his scholarship may not find that he has no time left for this after completing his prescribed task as a teacher, and who fail to comprehend that one is misplaced in a true university if he can merely retail what others have made known.
As yet, most of us who have been judged worthy of membership in the society of the Sigma Xi have acquired our status as investigators as a byproduct of our opportunity as teachers; for what are called research professors are few and far between, and organizations for investigation only are none too common. We find encouragement in the stimulating fraternal association. We touch at a tangent the productive activities, of colleagues in our own department or in related departments. We lay our little offerings before local or state or national gathering of our confreres, and come home with suggestions for bettering and amplifying our own activities. We get what we may out of an undigested and heterogeneous program, and give little thought to the assimilability in it of what we contribute to it.
We are individualistic to a surprisingly large degree. As a rule we are generous to a fault with what we have to offer to others and as a rule we are not greedy in seizing on such help as they offer to give to us; above all we are not markedly seekers after advice or direction. We enjoy the prerogatives of the present, but cling to the methods of the past.
From the time when learning awoke after the world's long sleep, when civilization began really to have meaning outside of very restricted circles, the occupation that has become our profession has resembled my Antillean century plants in following its inherent bent. The conditions of its environment have presented an increasingly harmonious optimum for its simple existence, with neither serious competition nor any great obstacle
interposed anywhere to its drift along the lines of least resistance-or in this case of greatest attractiveness. That conditions have changed is evident enough, but they have changed gradually and the changes have been in favoring directions.
The aggregate utility of what is called research had led, even, to its sedulous cultivation in a limited way: but even under cultivation it has shown few mutations unfitting it for continued existence if once more thrown over to the unrestricted action of natural selection. It has scarcely become domesticated. Its survival and increase have been of the fit rather than of the fittest, where change about us has been gradual and of degree rather than of kind, and where neglect rather than encouragement have favored it. It has resembled the wayside weed doing too little harm to be worth repression, and more or less useful for fodder or bedding-down when the trouble was taken to harvest its produce.
Almost suddenly we are confronted with totally different environing conditions. The last decade has seen an interest in scientific investigation that was unknown before. The period of the war has brought its real value to recognition. The harmless weed has been seized on as most promising for intensive cultivation. Its natural attributes are being selected and blended with a skill such as the agriculturist uses in bettering his crops and his stock. Its maximum development is favored by a more or less serious effort to remove or reduce disturbing competitors. The stigma that science, the organizer of knowledge, has not organized itself seems about to be removed.
"Tempora mutantur, et nos, in illis." The almost catastrophic changes that the last few years have brought into the human world is placing scientific research on a business basis. It is not too much to expect great things from its effective organization as a means to an end: or to expect it to yield quickly in orderly controlled team play results that individual fatuous effort could bring about slowly and disconnectedly if at all.
Is science capable of transplantation and cultivation under artificial conditions? If so, the product will differ from the original in kind as well as in degree quite as much as the highly specialized animals and plants of the farm do from their undomesticated prototypes. If so, its nature will have shown a plasticity to be looked for in nature hardly elsewhere than in the outgrowth of human intelligence.
Transplantation is actually at work. The investigating manpower of the world is being registered with startling rapidity, preliminary to preferred enrollment or selective conscription. There is scarcely a person here present who will not feel its force within a few years if the signs of the times are to be trusted. To the organizer, it promises new and enlarged opportunity for leadership. To the drudge it holds opportunity for the kind of shoulder-to-shoulder effort before which mountains crumble and the bowels of the earth yield up their secrets; but the drudge by birth is a rara avis among men moved by the real spirit of investigation, and the drudge from necessity is neither a happy nor always a profitable artefact.
That waifs and escapes from it will be found outside the cultivated fields is to be expected. Whether these shall profit the gleaner like strays of wheat, or foul the fleece like the carrots of the roadside, or prove all but baneful like the reverting parsnip, remains to be proved. In any event, if not destroyed, they may be counted on through the centuries to furnish vestiges of the old and primitive stock as rudiments for a new start when, if ever, the cultivation of research is abandoned-provided that the present cultivation is not so intensive as to destroy them utterly.
In the primitive desultory gratification of human interest in human environment lies the essence of investigation for investigation's
own sake. The amateur in science has entered, occupied uncontested the center, and is passing from the scene.
The largest creel of fish may be secured by seining or dynamiting or drugging the pool; and the largest bag of birds, by the skilful use of a net on a drizzly day. The market, unless glutted, will pay for the haul. But the sportsman does not wish to become a pothunter, and the naturalist knows that game must be protected to a reasonable extent if fishing and hunting are to continue and if sportsmanship is to endure. Forest and mine are most attractively exploited by organized onslaughts that take what it pays to take and sometimes leave a wake of destruction behind. The profit of the day is great, the rapid material progress to which it contributes is held to justify the attack: but what of the future?
Organization of attacks on the secrets of nature differ from organization of attacks on the material products of nature in this very essential respect, that the former do not destroy but rather bring the world's material resources to more effective and economic utilization. But is such purposeful organization likely to hamper or put an end to uncertain. That its survival will be through organized though purposeful and intelligent
That the new order will survive is almost
artificial rather than natural selection is probable. That it vill be a survival of the unlike is self-evident.
investigation? Is the seiner likely to foul the pool or barricade it against the sportsman?
Organization backed by a probable profit and loss sheet and a program for each enterprise once called a proposition, and now a business. Such project-enlists capital in organization and reinforcement are enlisting already, for research, capital looking to ultimate return, and also impersonal endowment because of the established repute of science as conducing to the general welfare of man.
To the investigator, investigation may become a renumerative profession when he bears his alloted share in cooperative effort. For the most part, up to the present he has paid amply for the privilege of doing such work; and to enjoy the privilege of doing it even on these terms he has rather gratefully if sometimes complainingly sold his services
as a teacher at a ridiculously low figure when measured by his training and talent.
He has done and is doing this under the spur of that most intangible but most essential trait of man that we call character, and because of those chimæras of the mind of man that we call ideals. Is he sanely enough balanced to conform his ideals to the trend of the times, to the chance for subordinating them to the broader plans of leadership; or are ideals never ideals when his own mind does not shape them, when from sport-which one pays for, they become work-for which one is paid? And if the zealot who can not modify his view still continues in our midst, as he must, is he to be weeded out; or allowed on sufferance to occupy the waste places of research; or to be kept purposefully from extermination, against a day when the nourishing hand of society may be withdrawn, and zeal in research again becomes synonymous with its primal meaning-devotion with all one's character to one's inborn ideal?
As we, the professionals in science who follow the amateur on to the stage, find ourselves marshalled in the ranks or leading the artisans of science, it may be well to remember that a Galileo, a Newton, a Berzelius and a Darwin lived and worked-not in vain— before the day of organization and intensive team work had dawned!
THE UNIVERSITY OF ILLINOIS
THE STRUCTURE OF THE HELIUM ATOM
ACCCORDING to the model which Bohr proposed in 1913, the helium atom consists of two electrons moving in a single circular orbit having the nucleus at its center. The electrons remain at the opposite ends of a diameter and thus rotate in the same direction about the nucleus. The angular momentum of each electron is assumed to be h/2′′, where h is the quantum constant. The ionizing potential of helium calculated by this theory is 28.8 volts. Recent experimental determinations by Franck and Knipping have given 25.4±0.25 volts. Bohr's theory is
approximately right but does not give the true structure.
For the hydrogen atom and helium ion, atoms containing but a single electron, Bohr's theory seems to be rigorously correct. For atoms containing more than one electron there are many facts which indicate that modifications or extensions are needed.
The chemical properties of the elements, particularly the periodic relationships and the phenomena of valence, have shown definitely that the electrons are not in general arranged in coplanar orbits. According to the theory which I advanced last year, the electrons in their most stable arrangements move only within certain limited regions about the nucleus, each of these cells containing not more than two electrons. The atoms of the inert gases were found to have their cells arranged symmetrically with respect to an equatorial plane, no electrons however ever lying in this plane. According to this view, the two electrons in the helium atom should not move in the same orbit but in separate orbits symmetrically located with respect to the equatorial plane. The two electrons in the hydrogen molecule (and in every pair of electrons which acts as a chemical bond between atoms) must be related to one another in the same way as those of the helium atom.
The most obvious model of this type is one in which the two electrons move in two circular orbits in parallel planes equidistant from the nucleus. By properly choosing the diameters of the orbits, the force of repulsion between the electrons is compensated by the component of the attractive force of the nucleus perpendicular to the plane. This model however proves impossible as it gives a negative value (-5.8 volts) for the ionizing potential.
A. Landé1 has recently proposed a model for the eight electrons of an octet in which each electron occupies a cell bounded by octants of a spherical surface. The eight electrons move in such a way that their positions are symmetrically placed with re1 Verh. d. phys. Ges., 21, 653, October, 1919.
spect to three mutually perpendicular planes which pass through the nucleus. When one electron approaches one of these planes it is retarded by the repulsion of the electron on the other side of the plane and is thus prevented from passing through the plane. Although each electron remains within a given octant of the spherical region about the nucleus, yet the momentum of the electron is transferred to the electrons in adjacent cells across the cell boundaries. In this model the momentum travels continuously around the atom in a circular path, being relayed from electron to electron. Thus even though the electrons do not leave their respective cells, the mathematical equations for their motion are very closely related to those which apply to the motions of electrons in circular orbits about the nucleus. Landé's calculations lead to the conclusions that this type of motion is less stable than one in which all eight electrons move in a single plane orbit. This objection can be overcome if we assume that the angular momentum of each electron is h/2 instead of the double value which is usually assumed for the electrons in the second shell. In fact, this conception gives grounds for believing that all electrons in their most stable positions in atoms, have orbits corresponding to single quanta and it is only because we have assumed coplanar orbits that we have been led to the conclusion that the outer orbits correspond to increasing numbers of quanta.
This model of Landé's has suggested to me that there should be a similar interrelationship between the two electrons of the helium atom, and also of the hydrogen molecule, and of the pair of electrons constituting the chemical bond.
I assume that the two electrons have no velocity components perpendicular to the plane which passes through the nucleus and the two electrons. The motion is thus confined to a single plane. The two electrons, however, are assumed to rotate about the nucleus in opposite directions, and in such a way they are always located symmetrically with respect to a line passing through the
nucleus. Consider for example that this line of symmetry is horizontal and that one electron is located directly above the nucleus at a unit distance, and is moving horizontally to the right. Then the other electron will be located at an equal distance below the nucleus and will move in the same direction and with the same velocity. If there were no forces of repulsion between the two electrons, and if we choose the proper velocities, it is clear that the two electrons might move in a single circular orbit about the nucleus, but in opposite directions of rotation. This would require, however, that the electrons should pass through each other twice in each complete revolution. When we take into account the mutual repulsion of the electrons, we see that their initial velocities will suffice to carry them only within a certain distance of each other, and they will then tend to return in the general direction from which they came. With properly chosen initial conditions the electrons will return back exactly on the paths in which they advanced and will then pass over (towards the left) to the other side of the nucleus and complete the second half of an oscillation. Each electron has its own orbit which never crosses the line of symmetry. The orbit however does not consist of a closed curve, but a curved line of finite length along which the electron oscillates.
Unfortunately the equations of motion for this three-body problem are difficult to handle and I have only been able to determine the motion by laborious numerical calculations involving a series of approximations. These however, can be carried to any desired degree of accuracy. By four approximations I have been able to calculate the path and the velocities, etc., to within about one tenth per cent. It is to be hoped that a general solution of this special type of three-body problem may be worked out, if indeed one is not already known to those more familar with this type of problem.
The results of this calculation show that the path of each electron is very nearly an are of an eccentric circle, extending 77° 58′ each
way from the mid-point (as measured from the nucleus). If we take the radius vector at the mid-point to be unity then the radius at the end of the arc is 1.138. The angular velocity of the electron at the mid-point of the path is such that if it continued with this velocity it would travel through 105° 23′ during the time that it actually takes to move to the end of its orbit (i. e., through 77° 58′).
By imposing the quantum condition that the angular momentum of each electron at the mid-point of its path shall be h/2", it becomes possible to calculate the radius vector and the velocity in absolute units. The radius vector for the electron at its midpoint is 0.2534 X 10-8 cm. which is 0.8359 of the radius of the orbit of Bohr's model (0.3031 X 10-8 cm.). Even at the end of the orbit the radius (0.2882 X 10-8 cm.) is less than that of the Bohr model. The angular velocity at the mid-point is 1.431 times that of electrons of the Bohr atom. The number of complete oscillations per second is 24.63 X 1015, which is 1.222 times as great as the number of revolutions in the Bohr atom (20.16 X 1015 per second). The total energy (kinetic plus potential) of the oscillating atom is 0.9615 of that of the Bohr atom. The ionizing potential of helium according to the new model should be 25.59 volts which agrees with Franck and Knipping's experimental determination within the limits of error given by them, but differs from the 28.8 volts given by Bohr's theory by nearly ten times the experimental error.
The oscillating model is thus not only satisfactory from a chemical point of view but is in quantitative agreement with the properties of helium. The fact that there I can be no corresponding structure with three electrons is in accord with the fact that lithium (which has three electrons) is an element having totally different properties from helium.
The calculation for the hydrogen molecule involves greater difficulties. Bohr's model with the two electrons moving in a single circular orbit gives a heat of dissociation of about 63,000 calories, whereas experiment
gives about 90,000. The calculations for helium have shown that the radius of the oscillating atom is considerably smaller than that of the Bohr atom, so that the force of attraction between the electrons and the nucleus is much (20 per cent. or more) greater. In the hydrogen molecule this increased force may result in drawing the two nuclei closer together thus increasing the stability of the molecule. Calculations of the orbits of the electrons in the hydrogen molecule are in progress.
The final results with a description of the methods of calculation will be published probably in the Physical Review and the Journal of the American Chemical Society. IRVING LANGMUIR
RESEARCH LABORATORY OF THE
ALFRED WERNER, professor of chemistry in the University of Zurich, died on November 15, 1919, at Zurich, Switzerland.
Professor Werner was elected an honorary member of the American Chemical Society at the general meeting held in New Orleans, La., April 1, 1915. It is now desired to leave upon the permanent records of this society a tribute to his genius and indomitable energy, and to the wealth of the contributions which he made to our science.
Born at Mulhausen in Alsace on December 12, 1866, he was educated at the technical schools of Mulhausen, Karlsruhe, and Zurich. Later he studied with Berthelot at Paris.
His first published work of note was upon the stereoisomerism of organic compounds containing nitrogen. Applying these theories to the unclassified mass of complex inorganic ammonia compounds, he realized the inadequacy of accepted ideas of valence to explain their constitution. Largely from a study of isomers among these complexes, whose consti
Tribute prepared by a committee of the American Chemical Society consisting of C. H. Herty, H. L. Wells and Arthur B. Lamb.