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Built-in wall cases for apparatus and chemical supplies, fitted with glass doors, add to the general appearance of the laboratory. All doors have friction catches and locks. The frame of the 24-in. by 30-in. hood is of wood and the sliding sash is counterpoised by lead weights attached by means of hemp rope. Foul air is conducted through a flue to the top of the building. A No. 35 Troemner balance rests upon a solidly constructed and seciirely fastened oak bench so t h a t there is only a negligible amount of vibration from passing street cars. It is protected from dust and fumes by a glass case which fits over the balance and is secured by locks. Opening from Che main laboratory is a special dark room provided with benches, sink, cases, and lockers. This room is
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used in conjunction with the course in photography and for photochemical work. In addition to the school library, a branch of the Public Library of the District of Columbia is housed in the school, making available a large number of books relating to chemistry and allied sciences. A museum has recently been started by the presentation of a collection of minerals and several collections of specimens representing processes of certain manufactured articles. To these will be added other minerals and certain chemicals prepared by the students. Instruction in chemistry is under the supervision of t h e Director of the Gducational Department and the instructors are chemists well trained in their profession.
THE CHANDLER LECTURE INTRODUCTORY REMARKS By Ralph H. McKee COLUMBIA UNIVERSITY, N E W YORK,N. Y .
I n 1910 friends of Professor Chandler, mostly former students, presented to the trustees of Columbia University a sum of money which constitutes the Charles Frederick Chandler Foundation. The income from this fund is used t o provide a lecture by an eminent chemist and to provide a medal to be presented to t h e lecturer in recognition of his achievements in science. We are gathered this evening t o listen to the Chandler Lecture and it is my privilege to introduce the lecturer, Dr. Willis Rodney Whitney.
MEDAL ADDRESS THE LITTLEST THINGS IN CHEMISTRY’ By W. R. Whitney GENERAL ELECTRIC COMPANY, SCHENECTADY, N. Y.
To receive the Chandler Medal is to me doubly agreeable. M y earliest interests in chemistry were largely influenced by what I heard as a boy about Professor Chandler and the Columbia School of Mines. At t h a t time he was t o me all there was of our science anywhere outside of Steel’s “Fourteen Weeks in Chemistry.” Through all of my lifetime he has been the American dean of chemistry. You may imagine my pride, then, in having my name thus connected with his. But a second reason for my pride and pleasure is the fact that I live in the city which first recognized the qualities of Professor Chandler, and am a member of the board of trustees which paid him his first professor’s salary. Therefore 1 shall show this medal a t Union with elation. T h a t he left our college to come to the Columbia School of Mines, where they paid no salaries, speaks well of Union, of New York, and of Professor Chandler. In preparing a n address which, while intimately connected with chemical affairs, might still be of interest to those who do not closely follow all its modern developments, i t has been my aim to select a field in which great activity has recently been taking place. I have made no attempt t o distinguish between chemistyy, physics, and electricity in this connection, because the littlest things of the universe clearly belong equally t o all three. Chemistry, physics, and electricity are cooperating in a thoroiigh manner in their study of nature and i t is evident that, from the viewpoint of this triple alliance, a wonderful new territory of interest has been opened. Possibly, also, by showing to the general public the exceedingly intimate relationships between the most theoretical and speculative parts of science and the highly prized technical applications, I may do something to encourage the younger men to appreciate the fact that the Copyrighted 1920 b y Columbia University Press, New York City.
theoretical and speculative may be also truthful, spectacular, and valuable. I have made no effort to appeal to the expert research physicist, nor to write for those who are actually doing advanced research work in the line of the littlest things in chemistry, but rather to the much larger and, I hope, less critical group who are interested in seeing how much ado can be made about next to nothing. One may also quite properly maintain that there is no such word as “littlest.” I may reply that there may also be no such thing as I talk about, but we get a great deal of satisfaction from thinking there is. My object is to treat in a simple way some of the facts which we have learned more or less recently which have to do with o u r chemically fundamental materials. Different chemists occupying various fields of activity would handle the subject differently according as they are impressed with different applications. Physicists would treat the whole subject from quite another standpoint. The mathematician would introduce a third, the metaphysicist another, and so on. I n the past, all have greatly advanced our knowledge. To most of us, these changing points of view are interesting largely in their application to some form of welfare work. I have had in mind the thought that I might talk about atoms, molecules, ions, and electrons, and still keep so well within the bounds of simple experimental demonstrations as to assist some of you in appreciating the applications. To those for whom such effort is unnecessary I would excuse myself by claiming a desire to help prepare the way for future students of the still more remote entity, the quantum, which i t seems chemists must soon adopt. It has always been natural to want to extend our vision. We have tried in vain to look through infinite space and to think through infinite time, though we know that we have no apparatus for such work. But, just as with telescope and microscope we have increased our knowledge within that portion which we may call our real horizon, without diminishing the incomprehensible total, so we have also advanced the frontiers of chemieaI or physical subdivisions (our metaphorical horizon), also without diminishing there the incomprehensible total. Everywhere we look there still extends that distant arrangement of something we vainly call matter and energy which, because of our limited measuring apparatus, we still know only as infinite complexity. But what we can put behind us with weights and measures attached, we say we have added to science, and whatever has not been successfully weighed or measured we justly consider unknown. Thus chemistry first started t o grow as a true and useful science when the balance came into use. So also psychology began as a science when i t could be built even ever so little on experimental and measured facts. But when one of the world’s greatest physicists tells us about things for which there are no generally useful measurements, or gives us data from untested balances, we seem justified in
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taking but passing interest. This will always ibc true in spite discrete and niunbered accurately. When they change their of the everlasting and infinite possibilities o i iutuie drvelopment. number b y the effect of temperature or because of chemical The more we realize the eomplevity n n d l h t i d e t d e d perfection activity, when some hretk down and others combinewe also of nature. which forces reverence and dcvotion from every know and count the effects. Never heiore was the belief in little true observer, the clearer we are that any specific knowledge particles callcd molecules so firm. The theoretical conceptions which lies beyond the reach of our apparatus is availnhlc only of atoms stem to have become the clearest of facts. The early through simple iaith and therefore, fortunately, equally to all, ideas were not bold enough, though they wcre rightly aimed. regardless oi apparatus. Tlw subdivisions of instter below the atom and down t o the ion Not long ago, we thought of the atom of matter as a hard, and electron are as certain as anything we know, and now energy round, indivisible something beyond wliicli we would prob:J,ly itself in thc qiiantum hypothesis is being given a minimum never need to look. The molecules were made up of such atonis dimension These result.: have come, not by matlitmatical or more or less bonded together and still with more or less freetlorn theoretical spcculation done, but through simple direct experiof motion. This limited freedom account?d, ior ednmple, for ments. the greater amount of heat required by complex molecules to SUSPI$KSIONS I N LIQUIDS mise their temperature than required by simpler tnolccules. I n agi~ruachingthe littlest things we may well start with But nowatlays the atom has become a regular solar system. suspensions in liquids. I& ennmple, sand in water seems Nothing is capable o i cxsimple and yet much of plaining its properties, disthe ,,,“St complex pl*ecovered in xcent years, iiomena of solutions can be short of removing from it found in this analogy. \arhen the sand is fine all the simplicity it was supposed to have, nnd adenough, yet visible under ding to it such new cointhe microscope, its suspiexitics as only incomprepcnried particles are alhensible celestial systems ways in a dancing sort of possess. This additive apmotion. We say this is preciation of matter apiiardue to the impacts of the eutly without reduction of invisible molecules and that the wholc combination is in the still unknown rethermal equilibrium; also mainder will always prothat the average kinetic ceed, but there are reasons energy o i all the particles is for each step, when taken, the same. What we say of because there is developed the sand is true of all SOILS the new apparatus for measuring the added appreof finely divided material, solid or liquid, and the finer ciation. the visible particle the It may seem strange that many of the facts whichled greater its amplitude of motion. Ultramicroscopes, investigators to discard the while still incapable of former ideas of hard disclosing molecules, disatoms have come from studies in a vacuum. close an ever-grealer activity of all suspended There, where we might matter the finer the state expect t.he least, we have of its subdivision. The found the most, and there, tendency of the sand to where now we ought to be able t o say we have a settle completely is so counteracted by this inclear uridcrstnnding of all dividual motion oi the possibilities, we must admit a still infinite field of uiiparticles that the final kllowns. state of balance is one W,i.i.iS K ” U N l l Y VIHITXIIY, CIII.I>,,IR 1,rCTUKSK As so many things have in which tke mncentrahappened i n VQCUO, I will approach the general subject tiorr of thc suspension varies with the height in the of the little things along this path. which ought to liquid. At this point any further settling is opposed by what offer fewer obstructions. The kinetic theory of gases we call the increased osmotic pressure of the suspension. This came to be something better than a theory and WAS a usciul enabled Parin to calculate from visible suspensions the cocnencollection of coordinated iacts with known laws, bcioie we knew tratioii of molecules or the number in any volume. His result that a t least a part of o w indestructible atoms were going to agrees with that obtained from other methods, but this method pieces. Thus while our theories have some of thcm hccome more interests us most as seeming most simple and dircct. The nearly laws, some of our laws have been r&pealcrl. In these suspended sand is also found to be electrically charged and affairs, however, facts have not suffered and the facts about the so resembles the ions o i an electrolyte. Under the influence of properties of atoms, for example, are the same old facts, only an clectromotivc force the particles migrate in one or the other they are augmented by new increments. In other words, what direction. Evidently the amount of charge per particle need we gain by our measurements usually remains, while what we not he a single unit and its sign may vary with the nature of the think with preconceiving thought may disappear. solution. Without blushing, wc nowadays refer to the number of moleCoLLolDS cules of gas per unit volume and know that whatever complicaAs the particles get smaller and approach atomic magnitudes tions they may individually involve, they are separate and the electrical quantities are more easily measured. The sus-
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pended particles act like dissolved salts. Positive colloids are precipitated by negative colloids just as the much smaller ions, silver and chlorine, precipitate each other. Albumen in an acid solution is positively charged and is negative in an alkaline solution, as though the charge was determined by absorbed H and OH ions. The tendency for aggregates to form by the union of dissolved or suspended matter and electric charges is a general phenomenon which is clearly shown when moisture is precipitated where air is ionized. In a soap solution McBain has shown that large suspended particles made up of aggregates of the hydrated fatty-acid radical exist as negative particles just like the sand particles, while the sodium or potassium exist as positively charged but single and separate atomic ions. Here we have in one solution a mixture of crystalloid and colloid electrochemical elements. This state, though last t o be discovered, might have been predicted from the charged atoms of the ions of Faraday and the charged colloidal suspensions of Graham and Hardy. A 5efinement of simple microscopic methods has carried our power of distinguishing particles of suspended matter down so close to the accepted dimensions of molecules that we must claim to have optical evidence of colloidal particles of some elements like gold and silver, which are actually smaller than the molecules of some other substances. This refinement is merely an extension of the method we employ in observing the dust in air traversed by a beam of light. Using concentrated light and ultramicroscopes, molecular dimensions and visible subdivisions of matter have been brought closely together. DIMENSIONS O F MOLECULES
Chemists who have absorbed from their first lessons the idea of molecule and atom have felt the necessity of seeing in equal volumes of different gases just the same number of molecules, because of the volume relations in gaseous reactions. They have also sensed the van der Waals equation, which mathematically expresses the fact that if we compress a gas made UP of discrete particles, however small, we finally reach a Point where tbey individually object t o being further crowded. When Pressed too closeb' they go out of the gas state and into the liquid or solid, and there i t is measurably much harder to compress them any closer together. These facts, through their mathematical expressions, long ago led t o fairly definite conclusions as t o number, size, and motions Of the molecules Of a gas. Everyone probably accepts the relative rates of diffusion of different gases through porous walls as a sign of differences in molecular sizes, and we would look for the relatively high diffusion rate of hydrogen as compatible with its small molecular dimensions. This diffusion process is apparently yielding wonderlul fruit at present, in showing that our particularly anomalous element, chlorine, with its unsympathetic atomic weight, is probably a mixture of two or more elements (isotopes) which have never before been separated. It has been through t h e studies connected with the smallest particles of matter that we have been led to try to separate such permanent old elements as chlorine into components. Without attempting to give exact numbers I may say that there are nearly 30 billion-billion molecules per cubic centimeter of air under ordinary conditions, and that when the first practical incandescent lamps were evacuated, they still contained over a million-million molecules of air. Before we proceed t o smaller dimensions I want you to get a closer view of the common molecules and some conception of their size. We are familiar with the sand on the seashore and it has long served as a measure of number. Assume that the grains average one-one-hundredth inch in diameter, a million could then fill one cubic inch. Let them represent our molecules. On this basis the molecules in a glass of water would suffice to cover the United States with such
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sand grains one hundred feet deep. We are forced by our measurements to accept such results before we can go further along this line. STUDIES I N VACUO
For forty years we have been continually devising new means of producing high vacua, not because the very highest is needed in a good incandescent lamp, although i t is, but because the further we went the more interesting became the results. With each new type of vacuum pump a few million more molecules were removed from the bulbs. This in turn usually called for a new apparatus t o measure the new vacuum and so the frontier over against nothingness was extended. It seems strange a t this late day to say that probably the best vacuum we can permanently maintain and accurately measure still contains over two billion molecules per cubic centimeter: that is, there are still one hundred times as many molecules in a well-evacuated lamp as there are people in the world. DISTILLATION IN vilcuo-With the candid acceptance of the gas molecules as real things, whether hard or soft, it was surprising how many physical facts became obvious. Such a simple observation as distillation of metal in vacuo is a case a t point. If a metal such as copper is distilled in a glass bulb, as by boiling it from a relatively infusible electrode or vaporizing it by an arc, it will be seen condensed on all parts of the walls, but, if this takes place in a fairly high vacuum there will be clean shadows formed on all shaded surfaces of the glass. I n other words, the copper distils in straight lines, and even a fine screen remote from the glass will produce a sharp shadow. This is all in accord with the fact that a t ordinary pressures the path of such vapormolecules is very short and there is so much mechanical interference that no shadows can form, but with the air molecules out of the way, the mean free path of the copper molecules, a t its low pressure, exceeds the dimensions of the bulb itself and practically all the copper distils in straight lines. GAS FLOW-Another interesting case is that of the rate of flow of a gas from a bulb into and through a capillary. When the is fairly high, so that the molecules of gas have a long average path free of interference with one another, the rate a t which they will pass out of the bulb and into the capillary is determined by the number which can strike on a surface of the bulb corresponding to the area of the capillary, and this is small. This that a t low pressure the rate of removal of a gas is very slow. For example, for a liter of gas a t a millionth atmosphere pressure to pass out through a tube I mm. in diameter and I O cm. long would require over 15 min. if i t were going into a perfect vacuum. A molecule can enter the capillary only when i t is aimed just right. If the area of its bulb is a million times that of the capillary there is only one chance in a million that it will leave the bulb on any round trip across it. EVACUATION-It is worth while in this connection just to mention the changes which have taken place in apparatus for producing high vacua, because without such improvements it would be impracticable to produce even those we now commercially require. Moreover, the new pumps, because of their method of operation, all conform to the requirements of the kinetic theory of gases. For high vacua the old reciprocating pump and the rotating oil pump are not enough. The so-called molecular pump of Gaede was an improvement. This is essentially a high speed revolving disc of metal, fitting so closely into a case or covering that the molecules of gas may be said to be bumped along in the direction of rotation. It marked a great advance. In the later diffusion pumps the gas to be removed is carried away by mercury vapor, into a stream of which vapor it is diffusing. I n neither of these pumps are there any of the plungers and valves which are common t o older pumps and which seriously limit the velocity and quality of the evacuation.
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We will now see how the studies in vacua led to submolecular magnitudes. In the early days of vacuum lamps Mr. Edison noticed the peculiar fact that from a hot filament a low current would always flow t o a metal plate located within the lamp, This soon became known as the Edison effect. It was peculiar and not clearly understood, but he showed that this current flowed only one way; t h a t is, the plate always became charged negatively, just as though negative electricity flowed from the hot filament to the cold plate. This was before the day of known electrons and there was no thought of using the phenomenon in the still undiscovered wireless and X-ray work as we do to-day, but the observations were published. I t was not until ure had become hardened to the conception of small mobile charges of electricity that the chemical significance of such phenomena began to appear. Now we look a t everything as made up of two kinds of electricity and we find this added peculiarity: the negative kind is everywhere a collection of one little unit with the same characteristics, from whatever source it is drawn. On account of its existence as the essential part of all matter, we are greatly interested in its properties. By its study, great progress is being made and the promise for future help is unlimited, though the work is scarcely begun. With the demonstration of the theory that gases are actually made up of molecules, the objection to considering other discrete particles, such as electrons, was reduced, and there is now a definite tendency to apply all the gas laws t o the electrons. We think of a metal as containing many electrons per atom, and we consider the electrical conductivity as due to the motion of these electrons. We look upon a hot metal as surrounded by a layer of negative electrons and when we apply a high negative voltage to the metal they shoot away from it. This is the source of the Edison effect. Sir William Crookes was the first to realize this as a state of matter, which we now call a stream of electrons. He observed in his vacuum tubes the negative or cathode ray which, first thought of as residual gas molecules electrically charged (and called by him a fourth state of matter), was finally conceived as made up of negative electric charges smaller khan atoms. These electrons have a mass corresponding to about one-eighteenhundredth of the hydrogen atom, which mass is due to and varies with the velocity. ELECTRON MASS-J. J. Thomson’s name is inseparably connected with the determination of the mass of the electron, the charge which it carries and the velocity of its motion. Produced in different ways in different gases or from metals in vacuo, by heat or by photoelectric effect, the properties of the electrons were found the same. They were counted by counting the particles of fog they could produce. Their charge was measured by the electric current which they could carry, and they were weighed and their velocity determined by their deflection in magnetic and electrostatic fields. cHARGE-It had long been believed that atmospheric air contained a few carriers of electricity, just as the purest distilled water does, because neither one is a perfect electrical insulator. I n Dr. Millikan’s wonderful experiments on the rate of fall of small oil drops between electrically charged plates, he showed not only that the air contained some pf these ions and that from time to time one was taken up by his oil drop, thus altering its rate of fall, but he also showed that the number of these charged ions in a given volume was reduced by partially evacuating the space and also that many more were produced in the air by the action of X-rays or radium rays. Moreover, as his oil drops were originally charged with a number of these units of electricity, it was probable that the friction produced in atomizing the oil had called forth on the oil drops some of these ions. This connects for us in an interesting manner the oldest electrical phe-
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nomenon of frictional electricity and the newest phenomenon of ionization of air by radium or X-rays. It also makes a new road for experiment because i t indicates that there are several simple ways of separating the same electrons from all kinds of matter and studying them and what they leave behind. This work has apparently proved t h a t when the ancient amber is rubbed a few more negative electrons are rubbed from the cat’s skin than from the amber and thereafter they merely perform the antics of regular standardized electrons. They may be counted and branded without alteration and are always the single identical little negative units of electricity. By quantitative observation Dr. Millikan accurately determined the amount of negative electricity which we must ascribe to each of the electrons-~~,~~o-millionths absolute electrostatic units. ELECTROLYSIS-When the current passes between copper plates in copper sulfate solution, copper passes through the solution as positively charged atoms or ions, while the sulfate ions with negative charge carry current in the opposite direction. This is easily measured, and the worg of Faraday gives us the quantitative relationships for such transport. While the charges per monovalent atom are the same as our electrons, these electrons do not occur separately from the atom in the solution and an electrolysis should, therefore, tell us the number of atoms in a volume of electrolytic gas. Perhaps the hydrogen electrolysis is the simplest illustration. Hydrogen forms with chlorine hydrochloric acid. It gives to the chlorine its negative electron and is thereby left positively charged; the chlorine becomes therefore negative. In the aqueous dissolved state the ions of hydrogen and chlorine are acting independently as influenced by the electric potential. As electrolysis takes place the hydrogen positively charged atom recovers a t the electrode a new negative electron and becomes ordinary atomic hydrogen. If now we compare the quantity of hydrogen gas obtained by our electrolysis with the quantity of electricity p u t into the process, assuming that each hydrogen atom takes one electron, we find that per gram of hydrogen gas produced there are required about 60,000 billion-billion electrons and t h a t therefore there are this number of atoms of hydrogen in one gram or about 30 X 1022 molecules. Since the gram corresponds t o about ten liters of hydrogen, we may say t h a t the cubic centimeter contains about one ten-thousandth OF this or thirty billionbillion molecules. This value, measured by electrochemical means, agrees with that obtained by entirely different methods and fixes the electrochemical electron as the electron of our vacuum tubes and decomposing elements. LUMINESCENCE-The fourth state of matter in the Crookes tubes is now the cathode ray composed of these ever-present negative electrons. When a beam of these electrons is directed a t low velocity against various chemical compounds, characteristic luminosity is produced which we know as fluorescence and phosphorescence, but when the impelling voltage is high enough, the velocity of the motion or these electrons is so great t h a t their sudden stoppage by impact within the atoms of matter produces the short waves which we call X-rays. These are characteristic of the internal structure of the material of the target of the X-ray tube. Thus, as will be seen later, we have gained much new information about the inside of atoms from X-ray studies. To repeat: A highly heated metal in. ~ J U C U Oemits negative electrons. These constitute a current which will flow in one direction only (negative from the hot surface to a cold one). This fact has become very important in a number of fields. It constitutes, for example, the simplest way to procure very high voltage direct current, as the production of high alternating voltages is simple and of this energy the thermionic vacuum tube will permit current to flow only in the one direction. WIRELESS-In its simple form of one hot filament and a cold electrode in vucuo this arrangement is called a valve tube. The valve tube is one of the most important pieces of apparatus con-
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nected with wireless communication. I n one form, a t the receiving station, it serves t o let the high frequency oscillating current from the antennae pass in a single direction only so that the telephone may be usefully affected. I n another case it is used a t the receiving station as magnifier or amplifier for the feeble current available. This case involves the direct control of a stream of electrons (a sort of cathode ray) by the interposition across the path of the rays of the delicate varying voltage received from the antennae. This effectively controls, triggers, or dams back a much greater current of electrons which are supplied by a local source of power. I n this way the slight variations of a feeble circuit control a much more powerful local circuit and thus act as multipliers of the wireless energy. This is using the electrons in accord with their known laws and, in fact, by the same static principle by which the mass and velocity of such electrons were determined by J. J. Thomson. This free handling of the electrons has led also to their use in the same form of vacuum apparatus, as generator of a current of high frequency from any source of alternating electrical energy. This oscillator, which still uses only the moving electrons in vacuo, is connected to an electrical capacity and inductance so that the potential of the energy rises and falls a t a rate depending on the impedance to its flow and the capacity of its temporary containers, much a s water in a U-tube may be made to oscillate in height when the rates of flow are properly controlled. .Thlls there are already a great number of technical applications of the properties of the free atomic fraction we call the electron. Although we know it in our arcs, our rectifiers, our X-ray tubes, our audions and pliotrons, the field has apparently only been scratched. With increased knowledge of electronic peculiarities we may expect greater advances in more complex environment than in our simple vacuum tubes or in the gaseous state. Naturally the phenomena OF chemical action and the solid and liquid state must offer a great field for new study in this direction. GAS I O N I Z A T i O N
When gas is present in the bulb with the hot electron-emitting cathode, the impact of these negative electrons on the gas molecules in some way breaks these latter down into other new negative electrons and positively charged remainders. I t is now known t h a t each atom of an element contains a definite number of these negative electrons. The number varies in regular order throughout the periodic table of elements. This process of ionizing is the separation of one of these electrons from the atom, the remainder of the atom being left with a positive charge including most of its original mass. This ionization produces an increase in conductivity of the path and serves as a n explanation, which we had long needed, of the fact that the electrical resistance of air quickly diminishes automatically on starting an arc, and an air-gap a t once becomes a short circuit, unless outside resistance is used to place an upper limit to the current 10. be permitted. Owing to the special properties of argon a t pressures of a few centimeters of mercury, the current-carrying power of the hotfilament rectifier is enormously increased through the presence and ionization of this gas; so that, instead of only a few milliamperes a t a very high voltage, it becomes possible to obtain several amperes a t a few volts rectified current. That is, the peculiar chemical nature of argon, owing possibly to the structure or arrangement of the electrons composing it, makes it fit well where no other gas will do as well. Thousands of rectifiers with this combination of thermionic emission and argon ionization are now being used commercially to charge storage batteries from alternating circuits. The older mercury rectifier is also a case of this kind. ELECTRIC ARCS
In connection with arc-lamp studies, I have lived through all apparently possible changes in the views on the phenomena of electric arcs. I n the early days there were men who thought
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that the electric current flowed in conductors in the positive direction, that is, as though it were made up of positive charges. Thus the early investigators looked for a passage of positively charged material of the electrode across the arc, and thought they found it. This seemed to represent the action of the carbon arc because the carbon anode wasted away much more rapidly than the cathode. Both were burning up in the air, however, and the anode being hotter, burned more rapidly. In vacuo, on the other hand, it became evident t h a t the phenomenon was quite complicated because simple distillation masked any regular electrical transport of matter. This was also finally found t o be the case with metals used as electrodes. For years there seemed to be no rhyme or reason in the material losses of arcing electrodes of any kind, whether these be burned in air, i n vacuo, or under water. Much research work was devoted to this subject. It was of the greatest technical importance. Our views are now simpler, if not really simple. We know t h a t arcs in chemically inert gases may be burned indefinitely without loss of either electrode. Weight losses occur only through direct evaporation (when the heat is not carried away fast enough by conduction) or through the combustion of the electrode. All these facts are illustrated by the commercial arc lamps of to-day. I n the carbon arc both electrodes waste away. I n the magnetite arc only one wastes away and that very slowly. In the mercury arc, where the mercury is really a non-consuming but necessary cathode, and in such arc lamps as tungsten in argon or mercury vapor, no change of either electrode occurs. We believe t h a t even in this case negative electrons cross the gap and their impact on the anode heats it, while the cathode has to be heated externally to produce the starting electrons. ATOM C O N T E N T
We have been forced, then, to recognize the electrons as part of all atoms. They are negative charges of exceedingly small mass but all alike. When one of these leaves an atom there remains a positively charged mass differing from the original neutral atom in this charge and in a very slight mass reduction. Thus we picture something much more complicated than hard, round atoms. I n the first place most of the volume of the atoms has all the properties of empty space. A very small part apparently carries all the useful attributes. This view was forced upon us when i t was shown that positively charged helium atoms may be fired through other atoms without apparently coming into contact either with electrons or the residual nucleus, except exceedingly rarely. It is this penetrability with its infrequent collisions which leads to the following enlarged picture of relative dimensions in atomic structures. We must apply the microscope to our grains of sand. A fair way is to start with the simple hydrogen molecule, which is the smallest, and examine one of its atoms. Other atoms will be similar but not simpler. The hydrogen atom may be looked a t as consisting of one standard negative charge or electron balanced by a positive charge or nucleus. As we need some mechanism to keep these two charges from merging entirely, it seems necessary t o adopt the celestial orbit with motion about the center of gravity. The atom, if spherical, has a diameter of about one one-hundred-millionth centimeter and the single electron a diameter four one-hundredthousandths as great. The nucleus, which is thought of as near or a t the center of the orbit of the electron, is very much smaller than the electron itself. We may say that, using the atom diameter as one mile, the electron would look like a baseball a t the end of the half-mile radius and the nucleus would be a positively charged pinhead a t the center of the circle. Moreover, this pinhead represents about 99.5 per cent of the total weight. There is much experimental evidence that the hydrogen atom can thus be best conceived of as a little solar system with the electron rotating about the nucleus. For example, there is a series of many lines in the hydrogen spectrum which have very striking mutual niimerical relationships. These are such that
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they could all be produced by the shifting of electrons from orbits greater than the least by simple successive multiples. That is, electrons which are driven out of their orbits by the electrical disturbance which produces a spectrum are thought of as giving the spectral lines by their orderly return t o their natural orbit about the nucleus. The different lines correspond t o the motion of the electrons in passing from exterior orbits back t o the unit orbit. The lines show by their wave-lengths that these orbits bear the relation t o the unit orbit of the squares of the simple whole numbers I, 2, 3,4,etc. The above Balmer spectral series of hydrogen would then be produced by the return of the baseball from different orbits after having been displaced to double, triple, etc., its normal distance from the atom center. The innermost orbit, as disclosed by the spectral lines, agrees in dimension wi h the over-all dimensions of the hydrogen atoms, otherwise determined. Some such thing seems probable when we accept the fact that the gas has t o be electrified, i. e., the atoms ionized or the electrons split off, before i t can become luminous or produce any spectrum. This again is a picture which conveys the thought that hydrogen a t least is mostly space, and that therefore this is probably true of everything. This in turn contradicts no known facts, as the properties for which we have a sense of appreciation like hardness may be given us by the stability of these little solar systems. No excuses are offered for the mechanical pictures we draw. They have always been drawn in chemistry and experience has shown that, whether true or false, progress is made through them. When X-rays and radium were discovered i t seemed that the bottom had dropped out of our elementary conceptions. Additional quantitative experiments have shown, however, that we always possess a t any time only an incomplete picture. Chemists always hoped t o see some form of Prout’s hypothesis proven, although they have thought for a century that no justifiable data were available. They tried to build all matter from one protyle stock, but failed. Yet nowadays the thing seems almost demonstrated. Everyone who had studied thermochemistry knew that the elements in any recognizable state whatever, even a t the absolute zero of temperature, contained energy, and that what we measured in thermochemical processes were only differences. But even with this view we were surprised when an element was found which gave off heat and decomposed continually, thus making us wonder about the others. We are now going to be forced to learn the energy content of each atom. X-RAY SPECTRA
If the present condition teaches anything, i t is that we are id the midst of a most interesting period of chemical development. That different elements must possess complicated internal mechanisms in order t o render any understanding of ordinary spectra possible has been recognized since Bunsen’s day. Modern X-ray studies promise t o make this problem clearer. Each element, when its atoms are struck by electrons (cathode rays) a t high enough velocity, emits a characteristic line spectrum, the wave-lengths of which vary progressively and by regular intervals from element to element throughout the entire series. No artificial story of any plot yet untested by literature could be more striking in human interest than this discovery by young Moseley, the Englishman who was unfortunately killed a t Gallipoli in 1915. He did more t o simplify all our elements than anyone else has ever done. For a century or more we had known ordinary spectral lines without being able t o understand them. They differed enormously from element to element and good men spent their lives studying them. Then the X-ray was shown to consist of light waves 10,000times shorter than ordinary light, but there was still no apparent way of producing interference, diffraction, or spectra. The wave-lengths were so short that no grating could be ruled for them. Yet it was natural t o
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t r y t o produce an X-light spectrum. This was accomplished through a wonderful conception of Laue in 1912,t h a t the almost infinitely small atoms which are spaced regularly in all crystals might be there arranged in such fine structure that they would do for X-light what the finest possible rulings of Rowland or the thin film of an iridescent soap bubble had done for ordinary light, i. e., produce a spectrum. A great hope was thus realized. The distribution of the energy of the total radiation of X-light could be disclosed by spreading out the different wave-lengths just as they are spread in a n ordinary spectrum. Moseley, in studying these spectra, which contain characteristic lines of relatively great brilliancy, discovered almost the first relationship of importance which we have obtained of any kind of spectrum. What Moseley showed, put into simple form, was t h a t the spectra of our chemical elements, produced by using them as sources of X-rays, differed one from another in a very simple, progressive, numerical manner. The spectral lines of one chemical element were found shifted a definite amount into shorter wave-lengths for the spectrum of the element of next higher atomic weight throughout all the elements tested. This, in its regularity, was even more striking than our periodic table, because it was not periodic but progressive and suggested simple synthesis of elements. It gave us every reason t o believe that our lightest known elementary atom contained one electron and that all other elements were derived one after another by t h e addition of one of these identical units of electricity. Naturally, since the atoms are electrically neutral, this means that t h e positive charge on the nucleus also increases by one unit for every additional electron. Thus the highest element of the series (uranium) contains 9 2 electrons and all elements fall in order between I and 92. This is like saying that everything in the universe (because we know that all celestial and terrestrial elements lie within the same range) is made up of different collections of the same little electrical bricks, that all numbers up to 92 are in use, but t h a t none are more complex than number 92. Moreover, all except five of the possible atoms with electron numbers between I and 92 correspond t o well-known elements. Five unknowns may yet be discovered. The analogy with ordinary light is quite perfect in the case of X-rays. Because of their exceeding smallness, electrons fired a t high velocity into a surface set into motion corresponding components of the atoms. These small electric charges thus vibrating and recovering their proper places cause the characteristic short wave of X-light. This corresponds to the ordinary light of longer wave-length which a mass of matter gives off when bombarded mechanically (as by friction) until red-hot. It is not surprising therefore t h a t the internal mechanism of t h e atom can t o a certain extent be disclosed by the X-ray spectrum. Without going too far into X-ray spectra, I want t o refer briefly t o the subject of crystal analysis, because that again is of the greatest chemical interest. We have always known of the crystallizing tendencies of many substances, without knowing whether everything crystallized or not. We have often wondered what determined the regular forms which most elementary and compound substances persist in assuming, how some substances possess more than one crystal form and so few possess identical forms. It also seems as though matter showed among its various crystalline forms about all the regular shapes geometrically obtainable. It is now becoming evident that our crystals are structures in which the atoms determine the form and unit dimensions by the natural distribution of their electrons, and i t is entirely unfair t o talk of a molecule of a crystalline substance at all, because any one atom is equally related t o more than the molecule conception permits. The atoms are arranged in brick-like regularity with distances between atom-centers of the dimension of the previously demonstrated atom-size. This the X-ray has shown.
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It has been shown experimentally that a selected beam of X-rays, on passing through the powder of a crystal, will produce on a photographic plate a group of lines or pattern corresponding t o the form of the crystal and t o the elements of which i t is composed. I n othef words, i t looks as though every crystalline substance was distinguishable from every other, even when in powder form, and that mixtures could be analyzed by the lines of these X-ray patterns. DECOMPOSITION OF ATOMS
I n considering the atom I chose hydrogen, the smallest, and said it was mostly empty space, except for one negative electron and a still smaller nucleus. This little negative unit seems to meet us everywhere, whether in the electric current of a wire, the thermionic emission of a hot body, the ionization of a gas or the conduction of a current through aqueous solutions. Probably one of its most striking appearances is as a free electron shot spontaneously from certain atoms, which thus indicate t h a t they are too complex to exist indefinitely. With negative and positive charges as building stones the elements may be built up or torn down. For from Moseley’s work i t became evident that the atoms of the elements differed progressively one from another by the presence of added pairs made up of electron and positive charge. The chemist’s periodic table taught him that the characteristic properties of the elements, such as valency, resided in the electrons of the outer portions or shell of the atom which probably rise in number successively from zero t o eight, as indicated by the groups of eight in the periodic table. This leaves the rest of the electrons in each case as a part of an inner core or nucleus. While there may well be some errors in the literature concerning the spontaneous decomposition of the heavier elements, it now seems very sure and quite acceptable that uranium, thorium, radium, and actinium are shooting out negative electrons and positively charged ions and changing accordingly into elements of lower complexity. Thus the heaviest elements of the chemist’s category gradually fall back into more stable forms, but disclose in doing so only negative electrons and positively charged helium atoms. These are the [?- and a-rays of the radioactive elements. I n this process i t need not surprise us therefore to find an X-light (the yray) produced during this electronic discharge. The effect of electrons upon the material of targets in the ordinary X-ray tube indicates t h a t X-rays identical with the radium y-rays might be expected when the impinging electrons have a speed corresponding t o several hundred thousand volts. X-ray tubes are usually operated below IOO,OOO volts, but the decomposing radium corresponds t o higher voltage and so its electrons produce shorter wave-lengths. QUANTA
With electronic conceptions we also begin t o see some relation between such phenomena as the photoelectric effects, the decaying elements and thermionic emission. What radium, uranium, etc., do a t any temperature equally well, potassium does when illuminated and all materials when sufficiently heated; that is, they all emit the same negative charges, the electrons. Thus the photoelectric cell is another one of those relatively insignificant things, which, like the decomposing element and the electron whose mass varies with its velocity, seem about to force us t o important changes in our views as t o the little things. We have long known that when light falls on certain metals, particularly sodium, potassium, and lithium in vacuo, a current of small magnitude flows negative from the metal; that is, the metal gives off negative electrons. This resembles the Edison effect referred to, but I t takes place from a cold metal and is independent of the temperature. The energy displayed by these fired electrons is apparently not obtained from the incident light, though this would be the logical conclusion. This seems unsatisfactory because the velocity of the escaping electrons, t h e force with which they are fired, is determined by the fre-
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quency or wave-length of the impinging light and not by its energy. A feeble energy seems to serve to shoot an electron with a force entirely out of proportion t o any actual energy which could have been collected by the electron from the light. Even when we pass from ordinary light through ultraviolet t o X-rays the same thing seems true. A beam’of X-rays striking metals or even gas molecules causes them to send out negative electrons with very high velocities corresponding to the very short wave-length of the X-rays. Moreover, the electrons shoot a t once apparently without waiting for light energy t o accumulate locally sufficiently t o account for this energy of motion. The thing happens just as though the metal already contained a lot of electrons loaded for firing, the energy being stored except for the triggering effect of a little energy of corresponding frequency. There seems perfect analogy in this case between ordinary light on metals causing electron emission a t certain velocities and X-light causing similar electron emission of much higher velocities. This may not be so bad if i t is true that the elements have in them billions of times more energy than we have formerly considered. This energy is disclosed by the radioactive elements in their decomposition. It becomes a question of the mechanism of the discharge of the electron with this stored energy, and how i t happens that the discharged electron assumes a velocity corresponding to the frequency of the incident light waves. This calls for the emission of energy in units or quanta instead of continuously. It makes us look for some mechanism like resonators differing in different elements, but something which can account for a discontinuous system of emission and absorption of radiant energy. Again, one of our greatest interests lies in chemical reactions. How do they proceed? We know from experiment how the temperature affects their velocity and are therefore not mentally disconcerted by explosions, nor surprised that Dr. Loeb finds the velocity of life in fruit-flies 300 per cent greater a t 30’ C. than a t 20’ C.; but we are bothered to explain the fact that we have various but fixed rates of first-order reactions instead of instantaneous processes. Why should some of the molecules of a given gas react when others do not? Something must give some of them what Marcelin calls the “critical increment” necessary for their activation. W. C. McC. Lewis has suggested that this energy is taken from space by some mechanism which responds only to definite oscillation frequencies, which are determined by the molecular structure. He believes that the reception of radiant energy as shown by absorption spectra of the reacting substance is t h e criterion, and that the individual molecule reacts when it receives a single quantum of energy of the particular frequency. This is the energy unit hv now generally accepted in radiation, where v is a frequency and h a universal electronic constant. In the case of the quantum relationship we also find support in the present view of the production of light in the line spectra of hydrogen. The lines are due not to the regular orbital motion of electrons, but t o the definite finite steps taken by the electrons in passing from outer to inner orbits. This makes it a little easier to get the conception of radiation units as required by the quantum relationship. The light is not continuous but is emitted in units hv, where v is the frequency and 12 a constant. I n general, an electromagnetic disturbance, a moving energy wave in space, has been imagined as produced by speed changes (not by regular motions) of electrons. If these are finite and their speed change finite, the resulting energy emission might be expected to be formed of finite energy units like the quanta. It is not my intention to try to bring you t o the very brink of the precipice of the entirely unknown. Some chemists and physicists must, with clear vision and unnatural perspicacity, work there, and continue to peer beyond the really visible. They must form new theories t o coordinate the recently dis-
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covered facts which will then direct the search for still better understanding and further knowledge. To the chemist, however, there is soon bound to come a great deal of new help from the studies of the structure of the atoms. As indicated above, this work might be thought or as started by Mendelejeff’s periodic system. There the electropositive and electronegative natures of the elements were arranged in order as functions of mass and the chemist hoped to find all elements made up of protyle units. But Sir William Crookes gave atomic composition its real pathway when he showed t h a t substances iw vacuo a t high voltages all shoot out the identical kind of negative electric particle. The electrical relationships were then made still more evident by the discovery t h a t the positively charged gas particles carry practically all the atomic weight. Thus in low vacuum apparatus these two kinds of matter or electric charges could be studied. Throuih the analyses of rays of moving negative electrons and the corresponding positive ions now easily obtainable we are thus led t o see more clearly a lot of little things which were heretofore indistinct. STRUCTURE OF ATOMS
The special activities of electrons in atoms is naturally a matter of great interest. There is so much accumulated information on the properties of elements, chemical and physical, that, having a conception of the number and identical character of the electrons, some useful picture of their arrangement in space seems possible. The first successful picture in this attempt was that of Bohr, which I have touched upon. Roughly stated, he pictured the electrons in their stable state as rotating in concentric circular orbits about a positive nucleus. Certain applications of external energy, like electrical bombardment, may disturb this state, b u t the tendency is then for the electrons to return to their proper orbits. I n this act of returning from a remote but simply related orbit luminous radiations are produced. Thus the lines of the element’s spectrum are conceived to be produced by the orbit-to-orbit motions of electrons, and this is in accord with the ideas we have of characteristiclightwave production. I n the case of hydrogen, as given above, there was a remarkable confirmation of the Bohr conception because, after his original publication, a new series of hydrogen spectral lines was discovered, and these, in conformity with the theory, are produced by the electron in returning to the innermost possible orbit for the hydrogen atom. The two other series, Balmer and Paschen (infra red), correspond quantitatively to the return of electrons from outer orbits to the second and third natural concentric orbits, respectively. Thus the positions of a large number of lines constituting a t least one element’s spectra are calculable on the assumption of regular concentric ring orbits having simple diameter relations of the squares of ascending numbers beginning with unity. It need not surprise us t o find the complications much greater when we come t o more complex atoms and we are evidently not very near a good method for calculation of the spectra in general. For the chemist it has seemed more satisfactory to try to place the electrons in stationary and geometrically regular positions in the atom, and a t present this need not necessarily interfere with the conception of motion of the electrons in hydrogen and helium, for example. It seems also quite possible that a per,petual orbital motion of all electrons in atoms may be made compatible with the fixity which the bonds of organic chemistry demand, by considering as the fixed points of attraction the centers or foci of circular or elliptical electronic orbits. By confining the electrons to simple, regular, geometric positions in spherical shells, many of the chemical and physical regularities are coordinated. G. N. Lewis and Langmuir have studied this subject with valuable results. I n this way the limited but varying valency of elements is made clearer and
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what we like to call reasons for the chemical activity of elements, their positive and negative natures and the inactivity or neutrality of such others as the argon group, are coordinated. For example, the inert gases are conceived as having in their outer shell a maximum or equilibrium-number of electrons which accounts for their inactivity. A natural tendency towards this type of structure for maximum stability is also looked upon as the reason for the chemical properties of the other elements. VALENCY
All the elements differ one from another in the number and arrangement of their electrons. This difference is expressed in the Mendelejeff table, for we have long recognized countless properties occurring with periodic regularity. It is no strain to our imagination, therefore, to picture the relative stabilities of aggregates of electrons as periodic functions of their number and even to find that eight is a peculiar key-number. If shells of eight are most stable, then both higher and lower numbered shells will be less stable and there will be a tendency for a group of nine to give up an electron and of seven to take on a new one. This conforms to the highly negative nature of fluorine, the well-known stability of neon, and the positive nature of sodium, which in accord with Moseley’s work have 7, 8, and g electrons, respectively. If this is a true picture, then we may as well attribute affinity to these electron differences and see in the dissociated form of sodium fluoride, for example, the liberality of the sodium with its one extra electron in accommodating the special avidity of fluorine for just that one electron. This leaves the sodium as a positive ion and the fluorine as a negative one. ’ Two fluorine atoms may be looked upon as bound together by the tendency of each to complete a n octet, which they do by sharing a. pair between them. I n this way chemical reactions and electrolytic dissociations are brought about through the tendencies of the electrons concerned to rearrange themselves in the most stable possible relationship with one another. This particular subject evidently merits much better attention than I can give it and I shall be satisfied if I have given you even a slight desire to follow it further. ISOTOPES
Some of our well-known elements are automatically going to pieces and others are having decomposition thrust upon them. Was there ever a more important period in the history of chemistry? The first proof of this atomic disintegration was the radical discovery that radium was a new, uncontrollable, and dangerous element which was shooting itself to pieces. This story of radium is another of those countless truths obtained through novel and distinctly quantitative measurements and orderly research, by which our powers of appreciation seem overtaxed. To many such things we seem a t first to turn a dulled edge of appreciation in order not to get big nicks in the sharper side of our senses. How could i t happen that, with our countless tons of old, reliable, available elements, we should have to get our greatest lesson from an element of which the whole world contained hardly enough for a necessary atomic weight determination? The answer as usual is found in quantitative measurements. The idea t h a t the atom of one element became the atom of another, by losing helium and negative electrons, had to be accepted, because there was no other acceptable interpretation of measured facts. Thus radium was shown to be decomposing by the discharge of relatively large, positively charged particles now known as helium nuclei of atomic weight four, and by the discharge of negative electrons of relatively negligible mass, These were the original a-and p-raya of the literature, the y-rays are the X-rays due to the subsequent actions of the p-particles. As the loss of the positively charged helium atom from any element meant a reduction of four in its atomic weight the question at once arose as t o what is wrong when, in the orderly decomposition of uranium through radium
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and polonium, we reach a point where the residual atom must have an atomic weight of exactly 2 0 6 . Lead appears a t this point in our old table with a weight of 2 0 7 . It must have taken great faith t o suggest that ordinary lead was a mixture. It called for further accurate work on atomic weights. Fajans and Soddy could predict this element with an atomic weight of 206, and i t had to be found in ordinary lead. No one was so well fitted for critical atomic weight work as Richards, therefore those most interested turned t o him. In 1914,he, together with Lembert, showed that lead from different sources certainly varied In atomic weight far beyond any possible error in manipulation and that ordinary lead is a mixture, one of whose components has a weight of 206. Elements composing such mixtures, previously considered single elements, are now called isotopes. This was another big little thing in chemistry which has done more for knowledge of atomic structure than anything within a century. It has opened the mind of the physicist and chemist to expect the unexpected and to take up again the apparently eternal search for the ultimate possibilities of nature. CANAL RAYS
Just as the negative electron had its determined through its deflection by a magnetic field, so the of the various positive ions have also been measured. The positive ions so far studied are the residues of gaseous molecules from which one or negative electrons have been detached by electrical means. They were studied by Thornson, Wien, and others in the cathode of a conducting Geissler tube, To the space handle them by themselves they are allowed to pass through a hole in the towards u,hich they are directed by the electromotive force. This beam, quite analogous to the cathode beam of negative electrons, is called the canal ray or positive ray, Under the simultaneous influence of static and magnetic fields placed at right angles t o each other, these ions describe parabolic curves which are recorded photographically, and thus the positive ions of w,hich the positive ray is were found to correspond in mass t o the respective atomic and molecular weights of the gases in the space. This is another of those wonderful developments vc.hich was started by a single almost insignificant and remote study of an atomic fraction. It is to-day leading us chemists to revise entirely our most elementary concept~ons, It is another big littlest thing. From the self-recorded curves of the positively charged ions of many of our presumably simple gases we are obtaining, through Thornson's work, entirely new light on their composit~on~In ionized nitrogen, for example, there are found single atoms of nitrogen with one and two positive charges afid nitrogen molecules with two and even three atoms sharing a single positive charge, but there is nothing but nitrogen present. this work, is finding that some of the supAston, posedly elementary gases are mixtures of isotopes. Argon, for example, may become a mixture of an element of exactly 40 atomic weight with a few per cent of another element of 36 atomic weight. Neon, m,?.hoseatomic weight was supposed to be 20.2, has been definitely proved to consist of two closely allied elements of exactly 2 o and 2 2 . Aston has thus determined Over forty atomic and molecular weights by his refinement of the positive ray method, and has found that without exception every one is a whole number. Thus the study of positive ions has led to the discovery of an entirely new field of phenomena in atoms, where the most refined measurements by physical and chemical will be necessary. The indications are that even our old intractable chlorine is t o be split up into a mixture of isotopes of 35 and 3 7 atomic weight. Evidence is therefore accumulating that all the real atomic weights are practically whole numbers and that the apparent fractional weights are due t o various mixtures of elements which in turn have whole-number atomic weights. -4mong the foremost in these opinions are Rutherford and
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Harkins who would build all the elements, even helium itself, out of the stuff in hydrogen; or, since this in turn is a positive nucleus and a negative ion, out of hydrogen nuclei and electrons. Rutherford believes he has actually produced the hydrogen nucleus from nitrogen by bombardment of nitrogen with helium nuclei, for, in this way, he obtained charged particles whose path-length was four times that of the helium nucleus and corresponded with that obtained by similarly decomposing hydrogen gas. No other explanation fits the facts. Harkins has discovered that the elements of greatest abundance are of even atomic weights and are practically exact multiples of that of helium. As this stability might be expected, compared to atoms with odd atomic weights, from stability data of radioactive decomposition, he likes to consider the helium nucleus as the weight basis of all the simpler elements of even atomic weight below nickel, and to see in the odd number atoms the additional mass of three hydrogen nuclei. Such elements as do not seem to correspond to this point of view will a t least have t o undergo a critical investigation as t o their right to exist. The positive nucleus is apparently the seat of what we call the atomic weight because the mass of the electron is insignificant compared to it. If these nuclei are built UP of hydrogen nuclei, all atomic weights will be its simpler multiples. Even with due consideration of probable isotopes, this does not exactly satisfy all the atomic weight data. The step now being taken is t o look for the necessary weight corrections in the principle of relativity. This expresses mass as equal t o the energy divided by the square of the velocity of light. The internal energy is evidently there in the atoms; and its quantity, if due t o or housed in the electrical charges, might be slightly different, in the case of an atom containing positive charges closely arranged, from that Of the energy Of the Same charges separated' The magnitude of such corrections, due t o the relativity principle, seems t o be of the proper dimension, and this will force the to study Whether we like i t or not we are proceeding along the path of conceptions new theory. We are producing new patterned after Old Ones, but pushed farther. One cannot see the end. There will be none. Starting with what we feel we know, if we are wise, we will always try t o extend it. What we knew Of molecules fbr a be measured by what we would expect from very small solid balls, but that period did not endure. Now, by reducing the size Of the components and by making them electrical, we have driven the centers of all properties into smaller common corners without making the final understanding any more simple, though i t is more orderly. The now has to in less much more than the atom formerly did, because we have found new regularities of nature, such cathode decomposing the properties of matter are accredited t o the smallest conceivable spots where the slightly understood negative electricity, in formerly unsuspected indivisible units, holds itself at a definite and respectable distance from positive electricity with which i t has always previously been considered as annihilating itself. I t s motions must produce light and carry heat. I t s immobility must account for cohesion and strength of materials and its collected and arranged groupings must determine all the differences of material with which we are familiar. And yet we d o well thus to force the issues. This may be proved by the fact that our chemistry has been built UP in this way and without it no Orderly, forward-looking chemistry Seems possible.
PRESENTATION OF THE MEDAL By Charles F. Chandler NEWYORK,N. Y .
It is my privilege t o present t o Dr. Willis Rodney Whitney the Chandler Medal. I appear as the representative of the more
