Transmutation of Metals.

Progress, Volume II, Issue 3, 2 January 1907, Page 95

Transmutation of Metals.

No one can observe and reflect upon even the simplest facts of nature, without soon coming to the conclusion that the thousands of different types of matter which we find about us m this world are not all independent and distinct substances ; for at every turn we see one form of matter being transformed into another, or two or three forms coming together and giving rise to a third. Thus, we heat water, and it changes into steam ; we touch a match to gunpowder, and it is gone ; but the smoke and odours m the air quickly inform us that some new substances have been produced. How many ultimate forms of matter are there then ? And how many of the manifold substances m the world are only com pounds of these elementary substances ? This question was first propounded thousands of years ago, and an absolutely certain answer has not yet been found. This does not mean, however, that no progress has been made towards its solution My purpose in the present article is to give a brief record of the attempts of man to unlock this most profound of natuie's secrets, and to show to what extent he has thus far succeeded, and what remains still unknown.

Greek Specula i ions 'Ihe earliest Greek philosopher, Thales, about HOO b c , taught that water is the fundamental principle of all things Xenophanes, who came a hundred years later, held that there weie two

fundamental principles — air and water ; while Hippocrates (460 to 377 8.C.), the "Father of Medicine," first launched the doctrine that there were four elementary substances— earth, air, fire, and water. His argument for a number of elements, instead of one, is rather naive It was something hkf this • — If man were composed of a single element, he could never be ill, but since he is at times ill, and requires complex remedies to keep him well, he must himself be complex. Aristotle, (380 to 322 8.C.) added to the four elements of Hippocrates a fifth — the ether, eternal and unchangeable, the ultimate substance of which the four elements are formed. And this Aristotelian philosophy of matter held sway throughout the Greek and Roman worlds, and down through the Middle Ages to the very dawn of modem science m about 1600 a.d.

The Answer or Alchemy. According to the Aristotelian philosophy, not only are all substances composed of earth, air, fire, and water, but the properties of different

substances depend upon the proportion in which these four elements are mixed. Furthermore, all substances were supposed to be transmutable into these four elements , and these four elements, in turn, transmutable into one another. Let us pause for a moment upon this seemingly strange doctrine, smce in it is found the explanation of the search for gold and the elixir of life, pursued so untiringly for fifteen hundred years by the ancient and mediaeval alchemists. If we could forget the discoveries of the last two hundred years, the doctrine would not seem to us at all absurd. Apply fire to ordinary water and what happens ? The water disappears into the air, and an earthy deposit is left in the vessel. In other words, when you mix fire and water in right proportions, you get earth and air. Similarly, since nearly all sub stances can be volatilised by heat, and smce nothing remains after the volatilisation except an ash or powder, is it not evident that mixing fire with any substance m the right proportion causes it to change into the elementary substances, earth and water ? Or, again, if we put salt or sugar into water, is it not apparently soon changed to water ? And if we add more fire, will not a larger and larger amount change into water ? Or, still again, if we take copper, or almost any metal, and put it into a strong acid, (a kind of water) does it not m time apparently disappear ? — that is, is it not apparently changed into a form of water ? Is it strange, then, that for so many years earth, air, fire, and water were considered the four elements, which only had to be mixed m the right proportions to produce any and all known substances ? 'I he alchemists, then, were not all charlatans. lhe> were simply men who were striving — most of them earnestly and seriously — to find the secret of producing any desired transformation of matter. They were trying to convert one substance into another by varying the proportions of the constituent elements. It was not unnatural that the principal object of their efforts should be the production of the substances which men most covet — namely, the precious metals, gold and silver. This however, was not their sole aim. They sought, lather, to find the great secret of the combination of the elements, not alone so that they might become rich, but so that they might learn to control matter, to prevent its disintegration when they wished — that is, to prevent death and disease. In the sixteenth century, especially, their attention was directed towards finding what they called sometimes the " Universal Solvent," sometimes the " Philosopheis' Stone," and sometimes the " Ehxii of Life," which are only different ways of describing that magic something which they honestly believed to exist, and which would have the power, when used under the control of the human will, of converting any form of matter into any other form. Some of the ablest minds of the Middle Ages were engaged in this search. Roger Bacon, Spinoza, Luther, and Leibnitz, all believed in the Philosophers' Stone and m the transmutation of the metals Now what did this search yield ? Did the alchemists find what they were after — the secret of the combination of the elements ? In a sense they did They learned that their efforts to transform the metals into one anothei were vain but at the same time, they learned that they could transform at will many kinds of substances into other substances. In other words, they learned the laws of the combination of many of the substances which with they worked, but not of nil They learned to control certain transformations of matter , but they learned that there were certain other forms which baffled all attempts to reduce them to any thing simpler ; and this is where alchemy began to pass over into modern chemistry. They learned that the old conception of the elements — earth, air, fire, and water — was quite insufficient to account for the results of their experiments , and toward the last of the eighteenth century, the last of the alchemists and the first of the chemists began to call all those substances which they were unable to reduce to any simpler forms, the elements The number of these elements has grown continually as investigation has progressed until to-day we lecognise about eighty such substances. These eighty odd elements are nothing more or less than substances which we have thus far been unable to i educe to simpler substances by means of any of the chemical reagents known to us. They are, how-

ever, the eighty substances into which we can easily transmute all of the two or three hundred thousand different kinds of substances which we are able to distinguish. It is obvious from this survey that the eighty odd substances which we now call the elements bear no trace of a resemblance to the elements of the ancients , so that when we speak to-day of the possibility of the transmutability of the elements, we have in mind something entirely different from what the ancient alchemists had when they used a similar expression. However, since all the metals known to the alchemists have now taken their places among the elements of modern chemistry, when we raise the question as to whether or not our modern elements are transmutable, we do indeed include in it one of the foremost queries of the alchemists— namely, are the metals transmutable ? This is the question which they answered from a priori considerations, m the affirmative, because they believed the metals to be nothing but combinations m different proportions of the four elements, earth, air, fire, and water. Now, what sort of answer does modern science give to this same question ? Let me divide the question into two parts First, have the elements been produced in nature's laboratory from a common substance, or from common substances ? In other words, have they been transmuted one mto another in the making of the world ? That is are they fundamentally transmutable ? Second, are they practically transmutable ? That is, can man ever hope to transmute them ? — can he hope to duplicate with the agencies at his command, m his own little pygmy laboratories, the processes which may be going on in the laboratories of nature ? I shall not be able to give an absolutely positive reply to either of these questions , but I shall attempt to show what the modern tiend of scientific opinion is, and to show something of the foundation upon which this opinion rests.

The Answer or Modern Chemistry. Doubtless, many a chemist who has worked for years with chemical reactions, and who knows all

the futile attempts which have been made during the past one hundred years to reduce the so-called elements to simpler forms, has come to feel that these elements are indeed ultimate, independent things, the original foundation stones out of which the universe is made But this has not been the view of the most far-seeing investigators in the domain of physical science, in 1811, the great Sir Humphry Davy wrote — " It is the duty of every chemist to be bold m pursuit To enquire whether the metals be capable of being decomposed and composed is the grand object of true philosophy." And Faraday, to whom physics and chemistry perhaps owe as much as to any other one man, said m 1815 :—: — ITo decompose the metals, to re-form them and to realise tne once absurd notion of transmutation are the problems now given to the chemist for solution." Also, in 1815, Prout put forward what is now

known as " Prout's hypothesis," which made hydrogen the primordial stuff, and all the other elements simply groups of hydrogen atoms. This hypothesis rested, so far as experimental evidence is concerned, upon the observed fact that the weights of many of the atoms are almost exact multiples of that of the hydrogen atom. But more careful weighing showed that this hypothesis wouldn't work — that there are some elements whose weights are not at all exact multiples of the weight of hydrogen Nevertheless, men kept seeking for connections and relationship between the elements, for to many a man the idea of a world built up of eighty different things, with no suggestion of a relationship between them, has been intolerable. In 1863 a new type of relationship was indeed discovered by a man by the name of John Newlands This discovery was developed chiefly by the Russian chemist Mendeleeff, and is now known under the name of " Merx-leleeffs Periodic Law." The essential thing in this law is this • If you write down in a horizontal iow the elements in the ordei of their atomic weights, leaving out hydrogen for the present, and, after getting up as far as fluorine, go back and start another row, putting that element which is eighth in order of weight under that which is first, the ninth under the second, and so on , and then, when you reach the fluorine column, go back again and put the sixteenth under the first, the seventeenth under the second, and so on, the elements in all the vertical columns are found to bear striking resemblances in both chemical and physical properties. The relationship is sometimes surprisingly close, as, for example, in the case of the alkali metals lithium, sodium, and potassium, or of the strong reducing agents oxygen, sulphur, and chromium. To go into a complete study of this so-called periodic law of the elements would be beyond the limits of this article ; but its immense significance may perhaps be understood if I say that it is necessary only to know the atomic weight of any element in. order to predict beforehand practic ally all of its chemical and physical properties. To convince ourselves of how certainly this relation shit) does eMst, we have only to have our attention called to one of the most remarkable scientific prophecies which has ever been made and verified [n 1871, when Mendeleeff first published his periodic table of the elements, he found it necessary to leave three blanks in his table, in order to get the related elements into vertical columns. He therefore jumped at the conclusion that three elements probably existed somewhere in nature, which had not yet been discovered, and which had the atomic weights which belonged to the blank spaces in his table. And so confident was he of his ground that he proceeded to predict very minutely the properties which these three elements would be found to have when discovered, judging of these properties from the properties of the other elements, which were in the same column. He told what their atomic weights would be ; what their specific gravities would be ; what colours, what solubilities and what combining powers they would have He never dreamed that he would live to see the discovery of these elements which he had so minutely described ; but m a very few years every one of them had been found, and they had exactly the properties which he had assigned to them. Now, let us ask ourselves what bearing this periodic law has upon the problem of the transmutabihty of the elements. First, it tells us in perfectly unmistakable terms that the elements fire not and cannot be independent, ultimate things, for it shows that they have relationships They group themselves into definite farmhes. It shows that if you add something to the weight of an element, you change in a perfectly definite and predetermined way its properties. Does not this point in an almost unmistakable way to the con elusion that the elements have a common origin , that they are built up from a common material ; and that our world is indeed at bottom, as Aristotle thought, something less complex than a compound of eighty different, independent things ?

The Answer of Modern Astronomy. Let us ne^t turn from chemistry to the study of the stars, and see whether this field of investigation has added anything to our knowledge of the transmit tability of the elements. It is now less than fifty years since the spectroscope was invented (1859) by the Germans, Kirchoff and Bunsen, the one a physicist and the other a chemist ; but this instrument has aheady added more to our knowledge of the stars than did all the work of the astrologers and astronomers who lived before its time. What has it taught ? Primarily these two things • — First, it has taught us to determine with certainty what elements exist m the sun and stars ; and, Second, it has given us a means of estimating the relative temperatures of the heavenly bodies. And it does this in a very simple way, for it separates into different coloured lights the complex

light emitted b> any glowing body, and thus enables us to determine just what colours are found in any given luminous source Since each different element emits a light of a characteristic colour, we have only to compare the colour of the light emitted by an incandescent element on the earth with the colour of the light emitted by the sun or by a star, to find whether tins particular element exists in the sun or star Again, since we find that when a body first grows hot enough to emit light the light given out is red, and that the hotter the body becomes, the more abundantly does it emit, first yellow, then green, then blue, then violet, and so on ; it is obvious that, if we find that of two bodies, which we can study only through their spectra, the one emits much more blue light, for example, than the other, then we may conclude that the first body is the hotter of the two Thus we have been able to make rough estimates of the temperatures of the stars , and Sir Norman Lockyer — perhaps the most noted of living astronomers, and the man to whom we are most largely indebted for the lebults given in this section —

has calculated that the hottest stars have temperatures as high as 30,000° Centigrade , and from this frightful degree of heat they run down^to about 5000° Centigrade, which is only about one thousand degrees higher than the temperature of the electric arc, the hottest temperature which we have so far been able to produce on earth. He estimated the temperature ot our sun as about 10,000 J Centigrade. Now, before we consider what the spectroscope has shown about the constituents of tne stars oi varying degrees of hotness, let us reflect upon the effect which we know temperature to have upon the compounds with which we are familiar on the earth. In general, the hotter a compound body becomes, the more does it tend to break up into its constituents, until, at the highest temperatures which we can produce on eartn, all known compounds are broken up into their constituent elements Now, if the elements themselves are compounds, as the Periodic Law would seem to indicate, what might we expect to happen to them if we could produce temperatures enormously higher than those attainable on earth ? It would be natural at least, to expect to find the elements themselves decomposed into simpler substances. Now, since these high temperatures exist in the sun and in the stars, it ought to throw much light upon our search to investigate the kind of substances which are present in the hottest stars. The following is the result of Lockyer's and other astronomers' studies with the spectroscope — The hottest stars consist almost exclusively of the very light gases hydrogen, helium, and a gas called " astermm," which is so far unknown on earth In the stars of somewhat lower temperature there begin to appear some of the heavier elements, like calcium and iron , and m the coldest stars we find nearly all the elements which exist on the earth In other words, as a general rule, as the temperature decreases, the elements put in their appearance — approximately, at least — in the order of their atomic weights. Since, then, a star which is very hot has but few elements, and since more and more appear as it grows cold, is not the evidence of modern astronomy at least as strong ts. the evidence of modern chemistry, that the heavier elements have evolved in nature's laboratory from the lighter ? In other words, that the elements are indeed transmutable ?

The Answer of Modern Physics. Such was the state of our knowledge up to about ten years ago No one had ever decomposed an atom Could it be done ? Out of the laboratory of the physicist came the answer. Yes, we can decompose atoms at will In 1879, Sir William Crookes began the study of the so-called " cathode rays," which appear in an exhausted tube, such as an X-ray bulb, when a discharge of electricity is produced within it. It was he who first brought forward the hypothesis that these cathode rays consisted of streams of projected particles shot with enormous velocities from the surface of the negative electrode. And these particles he thought to be, not atoms, but something much smaller than atoms. By the year 1898, it had been definitely settled, largely through the labours of Prof. J. J. Thomson, of Cambridge, England, that the cathode rays do indeed consist of particles of matter which have a mass only about 1-2,000 of that of the lightest of the atoms of the elements — namely, the atom of hydrogen Furthermore, no matter from what sort of metals these cathode rays come, or what the nature of the residual gas that is in the tube in which they are produced, these cathode-ray particles are always found to have precisely the same mass. Again, all hot bodies, when their temperatures are sufficiently high, are found to emit these same particles ; and, finally, the spectroscopic study of the effect of a powerful magnet upon light, has made it practically certain that it is the vibration of these same particles within the atom which produces light. The conclusion, therefore, seems to be inevitable, that these particles are constituents of all the elements ; and J. J. Thomson has brought forward the hypothesis that they themselves constitute the primordial stuff of which all matter is built up. Whether this hypothesis is correct or not, the experiments made upon cathode rays by many investigators — the foremost of whom have been Crookes, of London ; Thomson, of Cambridge , and Lenard, of Kiel, Germany — have shown beyond a doubt that the elements themselves are, under proper conditions, decomposable into simpler forms But the physicists have gone still farther than this T n 1896, the strange phenomenon of ladioactivity was discovered by Becquerel, of Pans , and physicists were groping about in the attempt to find an explanation of what it might mean, when Prof. Ernest Rutherford, of McGill University, Canada, solved the mystery He proved almost beyond a doubt that the radio-active elements — radium, uranium, and thorium — are actually in

the process of continual disintegration. Their atoms are continually shooting off from themselves, with stupendous velocities, minute particles of matter, some of which are the cathoderay particles themselves, and others of which are particles 4000 or 5000 times as large as these — that is, about twice as large as the atom of hydrogen. If you look into a so-called " spinthariscope " — an instrument invented by Sir William Crookes in 1903, and consisting of a tiny speck of radium placed just above a zinc sulphide screen and viewed with a common magnifying glass — you can almost see the particles projected. You do actually see the continual flashes of light to which they give rise when they impinge upon the zinc sulphide screen. Here, then, we are in the very presence of a disintegrating element. Have we yet found the products which are formed through this disintegration ? Yes, in part, at least. In 1903, Sir William Ramsay, and Frederick Soddy, of London, found with the spectroscope that helium was one of the products of the disintegration of radium. Prof. Rutherford's investigations have made it probable that there are quite a series of such products. He thinks that ordinary lead is formed in this way. Again, only last year, it was shown by Prof Boltwood, of Yale, and by Frederick Soddy, that radium itself is only a disintegration product of uranium Hence, in the phenomenon of radio-activity we are actually in the presence of the transmutation of some of the elements into other elements. The three elements which thus far have been shown to exhibit this property — namely, radium, uranium, and thorium — possess the heaviest atoms of any of the elements. And these heavy atoms are spontaneously disintegrated into simpler forms. I have given the answer of modern science to the first of the questions which we set out to answer. Chemistry has proved that the eighty elements are not independent, ultimate things. Astronomy and chemistry together have rendered it probable that all the elements are simply stages in the evolution of matter from simple into complex forms, the organic life which exists on the earth being simply the later end of this process of evolution from the simple toward the complex. Physics has found a way of producing out of ordinary atoms minute cathode-ray particles which are much smaller than atoms, and has albo found that certain of our heaviest elements are in the very act of spontaneously transmuting themselves into simpler forms. To our first question, then, as to whether the elements are transmutable in the laboratories of nature, we may return the answer that certain of them, at least, are trans mutable ; and it is probable that in nature's laboratories all of them are being produced from some simple, primordial stuff. Let us turn, now, to the second quebtion — Can man effect the transmutation ? Thus far he has indeed learned how to obtain cathoderay particles from any of the different forms of matter ; but he has not learned how to produce by any of the agencies at his command, any of the eighty recognised elements from any other He has caught nature in the very act of doing it herself ; but none of the agencies now known to the chemist or to the physicist appear to be able either to accelerate or to retard the process, that is, to change in any way the rate at which radio-active substances are spontaneously transmuting themselves into other substances It seems probable from the results already given, that the " Universal Solvent " which will produce this transmutation, and which is perhaps producing it now in the stars, is tempeiature , that the old Greek philosophers were right m assuming that a proper admixture of their old element, fire, would produce any desired transformation. But, unfortunately, the temperatures required to produce these changes, are probably for ever beyond man's reach The relatively little changes which we are able to produce on earth have no measurable effect at all upon the transmutations which uranium, radium, and thorium are undergoing. Although, then, our modern science has opened out before us a view which the ancient alchemist never had, of the wonderful operations going on in nature's laboratories, we are at the present day just as impotent as they in the face of the problem of the transmutation of any element into any other element If the secret of this transformation should ever be found we should be able to unlock almost infinite stores of energy which we now know to be wrapped up in the atoms of the elements The lamented Curie, whose untimely death has robbed science of one of her most gifted sons, proved in 1903 that the disintegration of a gramme of radium liberates at least 300,000 times as much heat energy as is evolved in the combustion of one gramme of coal. Furthermore, it is extremely probable that similar enormous quantities of energy are locked up in the atoms of all substances existing there in the form of the kinetic energy of rota-

tion of the cathode-ray particles, now commonly called electrons. J. J. Thomson estimates that enough energy is stored up in one gramme of hydrogen to raise a million tons through a hundred yards It is not improbable that it is the transformation of this sub-atomic energy into heat which maintains the temperature of the sun. Should man ever be able to unlock this energy, he would doubtless look back upon the day in which his progenitors burned coal to warm their houses and to drive their engines, with the same curiosity and pity with which we look back upon the day when our naked ancestors ploughed their fields with a crooked stick, and lit their fires with the spark from a flint. — Technical World.