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The Elements

Their Inter-relation and Origin

SIR WILLIAM RAMSAY, in his recent presidential address before the British Association, dealt principally with some of the fundamental facts regarding the elements, the.relations between them, and those remarkable side lights upon their nature and origin which have of late years fiashed out from the discoveries of Becquerel, the Curies, and their followers. No small share both in the experimental development of the new field thus opened, and in the theoretical discussions of the bearing of these remarkable discoveries upon the origin of the elements has been taken by Sir William Ramsay himself; this fact lends a special interest to the account of his presidential address, published in Nature and reproduced in abridged form below. After briefiy reviewing the ideas of the ancients 1'3- garding their so-called elements, the speaker went on to a discussion of the elements in the modern conception of the word. Since Dalton's days the chemist has been in the habit of regarding compounds as consisting of aggregations of atoms of elements, united in definite proportions Yet the more daring spirits, even of Dalton's days, were not without hope that the elements themselves might prove decomposable. Davy, indeed, went so far as to write, in 1811: “It is the duty of the chemist to be bold in pursuit; he must recollect how contrary knowledge is to what appears to be experience.... To enquire whether the elements be capable of.being composed and decomposed is a grand object of true philosophy.” And Faraday, his great pupil and successor, at a later date, 1815, was not behind Davy in his aspirations, when he wrote: “To decompose the metals, to re-form them, and to realize the once absurd notion of transformation—these are the problems now given to the chemist for solution.” Indeed, the ancient idea of the unitary nature of matter was in those days held to be highly probable. It has been customary for several years past to publish annually a table of the atomic weights, revised by a special committee. In the table for 1911, of eighty-one elements no fewer than forty-three have recorded atomic weights within on.e-tenth of a unit above or below an integral number. Karl Pearson assures us that the probability against such a condition being fortuitous is 20,000 millions to one. Such a fact as this almost irresistibly forces us to the conclusion that the elements are in some way related as to their mode of origin. The relation between the elements, has, however, been approached from another point of view. The^ periodicity in the properties of the elements, as pointed out by Newlands and Mendeleeff, makes it practically impossible for us to conceive of these elements as independent entities. A consideration of Mendeleeff's table naturally suggests the question as to the proper position in that table of the newly discovered radio-active elements and their congeners. Says Sir William Ramsay: “The discovery of radioactivity by Henri Becquerel, of radium by the Curies, and the theory of the disintegration of the radioactive elements, which we owe to Rutherford and Soddy, have indicated the existence of no fewer than twenty-six elements hitherto unknown. To what places in the periodic table can they be assigned? But what proof have we that these substances are elementary? Let us take them in order. “Beginning with radium, its salts were first studied by Madame Curie; they closely resemble those of barium—sulphate, carbonate, and chromate insoluble; chloride and bromide similar in crystalline form to chloride and bromide of barium; metal, recently prepared by Madame Curie, white, attacked by water, and evidently of the type of barium. The atomic weight, too, falls into its place; as determined by Madame Curie and by Thorpe, it is 89.5 units higher than that of barium; in short, there can be no doubt that radium fits the periodic table, with an atomic weight of about 226.5. It is an undoubted element. But it is a very curious one. For it is unstable.. Now, stability was believed to be the essential characteristic of an element. Radium, however, disintegrates—that is, changes into other bodies, and at a constant rate. if 1 gram of radium is kept for 1,760 yeai's, only half a gram will be left at the end of that time; half of it will have given other products. What are they? We can answer that question. Rutherford and Soddy found that it gives a condensable gas, which they named “radium--emanation;” and Soddy and I, in 1903, discovered that, in addition, it evolves helium, one of the inactive series of gases, like argon. Helium is an undoubted element, with a well-defined spectrum; it belongs to a well-defined series. And radium-emanation, which was shown by Rutherford and Soddy to he incapable of chemical union, has been liquefied ana solidified in the laboratory of University College, London; its spectrum has been measured and its density determined. From the density the atomic weight can be calculated, and it corresponds with that of a congener of argon, the whole series being: helium, 4; neon, 20; argon, 40; krypton, 83; xenon, 130; unknown, about 178; and niton (the name proposed for the emanation to recall its connection with its congeners, and its phosphorescent properties), about 222.4. The formation of niton from radium would therefore be represented by the equation: radium (226.4) helium (4) + niton (222.4). Niton, in its turn, disintegrates, or decomposes, and at a rate much more rapid than the rate of radium; half of it has changed in about four days. Its investigation, therefore, had to be carried out very rapidly, in order that its decomposition might not be appreciable while its properties were being determined. Its product of change was named by Rutherford “radium A,” and it is undoubtedly deposited from niton as a metal, with simultaneous evolution of helium; the equation would therefore be: niton (222.4) = helium (4) + radium A (218.4). But it is impossible to investigate radium A chemically, for in three minutes it has half changed into another solid substance, radium B, again giving off helium. This change would be represented by the equation: radium A (218.4) = helium (4) + radium B (214.4). Radium B, again, can hardly be examined chemically, for in twenty-seven minutes it has half changed into radium CI In this case. however, no helium is evolved; only atoms of negative electricity, to which the name 'electrons' has been given by Dr. Stoney, and these have minute weight, which, although approximately ascertainable, at present has defied ili- reet measurement. Radium C1 has a half-llfe of 19.5 minutes; too short, again, for chemical investigation; but it changes into radium C2, and in doing so, each atom parts with a helium atom; hence the equation: radium C1 (214.4) = helium (4) + radium C' (210.4). In 2.5 minutes, radium C is half gone, parting with electrons, forming radium D. Radium D gives the chemist a chance. for its half-life is no less than sixteen and -a half years. Without parting with anything detectable, radium D passes into radium E, of which the half-life period is five days; and, lastly, radium E changes spontaneously into radium F, the substance to which Madame Curie gave the name 'polonium' in allusion to her native country, Poland. Polonium, in its turn, is half-changed in 140 days with loss of an atom of helium into an unknown metal, supposed to 1:>e possibly lead. If that be the case, the equation would run: polonium (210.4) = helium (4) + lead (206.4). But the atomic weight of lead is 207.1, and not 206,4; however, it is possible that the atomic weight of radium is 227.1, and not 226.4. We have another method of approaching the same subject. It is practically certain that the progenitor of radium is uranium; and that the transformation of uranium into radium involves the loss of three alpha particles; that is, of three atoms of helium. The atomic weight of helium may be taken as one of the most certain; it is 3.994, as determined by Mr. Watson, in my laboratories. Three atoms would therefore weigh 11.98, practically 12. There is, however, still some uncertainty in the atomic weight of uranium; Richards and Merigold make it 239.4; but the general mean, calculated by Clarke, is 239.0. Subtracting 12 from these numbers, we have the values 227.0, and 227.4 for the atomic weight of radium. It is yet impossible to draw any certain conclusion. The importance of the work which will enable a definite and sure conclusion to be drawn is this: For the first time, we have accurate knowledge as to the descent of some of the elements. Supposing the atomic weight of uranium to be certainly 239, it may be taken as proved that in losing three atoms of helium, radium is produced, and, if the change consists solely in the loss of the atoms of helium, the atomic weight of radium must necessarily be 227. But it is known that (3-rays, or electrons, are also parted with during this change: and electrons have weight. How many electrons are lost is unknown; therefore, although the weight of an electron is approximately known, it is impossible, to say how much to allow for in estimating the atomic weight of radium. But it is possible to solve this question indirectly, by determining exactly the atomic weights of radium and of uranium; the difference between the atomic weight of radium plus 12, i. e., plus the weight of three atoms of helium, and that of uranium, will give the weight of the number of electrons which escape. Taking the most probable numbers available, viz., 239.4 for uranium, and 226.8 for radium, and adding 12 to the latter, the weight of the escaping electrons would be 0.6. The correct solution of this problem would in great measure clear up the mystery of the irregularities in the periodic table, and would account for the deviations from Prout's Law, that the atomic weights are multiples of some common factor or factors. I also venture to suggest that it would throwlight on allot.ropy, which in some cases at least may very well be due to the loss or gain of electrons, accompanied by a positive or negative heat-change. Incidentally, this suggestion would afford places in the periodic table for the somewhat overwhelming number of pseudo-elements, the existence of which is made practically certain by the disintegration hypothesis. Of the twenty-six elements derived from uranium, thorium, and actinium, ten, which are formed by the emission of electrons alone, may be regarded as allo- tropes or pseudo-elements; this leaves sixteen, for which sixteen or seventeen gaps would appear to be available in the periodic table, provided the reasonable supposition be made that a second change in the length of the periods has taken place. It is above all things certain that it would be a fatal mistake to regard the existence of such elements as irreconcilable with the periodic arrangement, which has rendered to systematic chemistry such signal service in the past. “Attention has repeatedly been drawn to the enormous quantity of energy stored up in radium and its descendants. That in its emanation, niton, is such that if what it parts with as heat during its disintegration were available, it would be equal to three and a half million times the energy available by the explosion of an equal volume of detonating gas—a mixture of one volume of oxygen with two volumes of hydrogen. The major part of this energy comes apparently, from the expulsion of particles (that is, of atoms of helium) with enormous velocity. It is easy to convey an idea of this magnitude in a form more realizable, by giving it a somewhat mechanical turn. Suppose that the energy in a ton of radium could be utilized in thirty years, instead of being evolved at its invariable slow rate of 1,760 years for half-disintegration, it would suffice to propel a ship of 15,000 tons, with engines of 15,000 horse--power, at the rate of 15 knots an hour, for thirty years—practically the lifetime of the ship. To do this actually requires a million and a half tons of coal. 1t is easily seen that the virtue of the energy of the radium consists in the small weight in which it is contained; in other words, the radium-energy is in an enormously concentrated form. I have attempted to apply the energy contained in niton to various purposes; it decomposes water, ammonia, hydrogen chloride, and carbon dioxide, each into its constituents; further experiments on its action on salts of copper appeared to show that the metal copper was converted partially into lithium, a metal of the sodium column, and similar experiments, of which there is not time to speak, indicate that thorium, zirconium, titanium, and silicon are degraded into carbon; for solutions of compounds of these, mixed with niton, invariably generated carbon dioxide; while cerium, silver, mercury, and some other metals gave none. One can imagine the very atoms themselves, exposed to bombardment by enormously quickly moving helium atoms, failing to withstand the impacts. Indeed, the argument a priori is a strong one; if we know for certain that radium and its descendants decompose spontaneously, evolving energy, why should not other more stable elements decompose when subjected to enormous strains? This leads to the speculation whether, if elements are capable of disintegration, the world may not have at Its disposal a hitherto unsuspected source of energy. If radium were to evolve its stored-up energy at the same rate that gun-cotton does, we should have an undreamed-of explosive; could we control the rate we should have a useful and potent source of energy, provided always that a sufficient supply of radium were forthcoming. But the supply is certainly a very limited one; and it can be safely affirmed that the production will never surpass, half an ounce a year. If, however, the elements which we have been used to consider as permanent are capable of changing with evolution of energy, if some form of catalyzer could be discovered which would usefully increase their almost inconceivably slow rate of change, then it is not too much to say that the whole future of our race would be altered. “The whole progress of the human race has indeed been due to individual members discovering means of concentrating energy, and of transforming one form into another. The carnivorous animals strike with their paws and crush with their teeth; the first man who aided his arm with a stick in striking a blow discovered how to concentrate his small supply of kinetic energy; the first man who used a spear found that its sharp point in motion represented a still more concentrated form; the arrow was a further advance, for the spear was then propelled by mechanical means; the bolt of the crossbow, the bullet shot forth by compressed hot gas, first derived from black powder, later, from high explosives; all these represent progress. To take another sequence: the preparation of oxygen by Priestley applied energy to oxide of mercury in the form of heat; Davy improved on this when he concentrated electrical energy into the. tip of a thin wire by aid of a powerful battery, and isolated potassium and sodium. Great progress has been made during the past century in effecting the conversion of one form of energy into others, with as little useless expenditure as possible. Let me illustrate by examples: A good steam-engine converts about one-eighth of the potential energy of the fuel into useful work; seven-eighths are lost as unusued heat and useless friction. A good gas-engine utilizes more than one-third of the total energy in the gaseous fuel; two-thirds are uneconomically expended. This is a universal proposition; in order to effect the conversion from one form of energy into another, some energy must be expended uneconomically. If A is the total energy which it is required to convert; if B is the energy into which it is desired to convert A; then a certain amount of energy, C, must be expended to effect the conversion. In short, A = B + C. It is eminently desirable to keep C, the useless expenditure, as small as possible; it can never equal zero, but it can be made small. The ratio of C to B (the economic coefficient) should therefore be as large as is attainable. The middle of the nineteenth century will always be noted as the beginning of t he golden age of science; the epoch when great generalizations were made, of the highest importance on all sides, philosophical, economic, and scientific. Carnot, Clau- sius, Helmholtz, Julius Robert Mayer abroad, and the Thomsons, Lord Kelvin and his brother James, Ran- kine, Tait, Joule, Clerk Maxwell, and many others at home, laid the foundations on which the splendid structure has been erected. That the latent energy of fuel can be converted into energy of motion by SIR WILLIAM RAMSAY, K.C.B., F.R.S. means of the steam-engine is what we owe to New- comen and Watt; that the kinetic energy of the flywheel can be transformed into electrical energy was due to Faraday, and to him, too, we are indebted for the reconversion of electrical energy into mechanical work; and it is this power of work which gives us leisure, and which enables a small country like ours to support the population which inhabits it. I suppose that it will be generally granted that the Commonwealth of Athens attained a high-water mark in literature and thought, which has never yet been surpassed. The reason is not difficult to find; a large proportion of its people had ample leisure, due to ample means; they had tim,e to think, and time to discuss what they thought. How was this achieved? The answer is simple: each Greek freeman had on an average at least five. helots who did his bidding, who worked his mines, looked after his farm, and, in short, saved him from manual labor. Now, we in Britain are much better off; the population of the British Isles is in round numbers 45 millions; there are consumed in our factories at least 50 million tons of coal annually, and 'it is generally agreed that the consumption of coal per indicated horse-power per hour is on the average about five pounds.' (Royal Commission on Coal Supplies, Part 1.). This gives seven million horse-power per year. How many manpower are equal to a horse-power? 1 have arrived at an estimate thus: A Bhutanese can carry 230 pounds plus his own weight, in all 400 pounds, up a hill 4,000 feet high in eight hours; this is equivalent to about one-twenty-fifth of a horse-power; seven million horsepower are therefore about 175 million man-power. Taking a family as consisting on the average of five persons, our 45 millions would represent nine million families; and dividing the total man-power hy the number of families, we raust conclude that each British family has, on the average, nearly twenty 'helots' doing his bidding, instead of the five of the Athenian fam5ly. We do not appear, however, to have gaine.d more leisure thereby, but it is this that makes it possible for the British Isles to support the population which it does. We have in this world of ours only a limited supply of stored-up energy; in the British Isles a very limited one—namely, our coalfields. The rate at which this supply is being exhausted has been increasing very steadily for the last forty years. In l870 110 million tons were mined in Great Britain, ami ever since the amount has increased by three and a third million tons a year. The available quantity of coal in the proved coalfields is very nearly 100,000 million tons; it is easy to calculate that if the rate of working increases as it is doing our coal wiU be completely exhausted in 175 years. But, it will be replied, the rate of increase will slow down. Why? It has shown no sign of slackening during the last forty years. Later, of course. it must slow dcw^ when coal grows dearer owing to approaching exhaustion. It may also be said that 175 years is a long time; why, I myself have seen a man whose father fought in the '45 on the Pretender's side, nearly 170 years ago! In the life of a nation, 175 years is a span. This consumption is still proceeding at an accelerated rate. Between 1905 and 1907 the amount of coal raised in the United Kingdom increased from 236 to 268 million tons, equal to six tons per head of the population, against three and a ha|f tons in Belgium, two and a half tons in Germany, and °ne ton in France. Our commercial supremacy and °ur power of competing with other European nations are obviously governed, so far as we can see, by the relative price of coal; and when our prices rise owing to the approaching exhaustion of our sup- we may look forward to the near approach of famine and misery. Having been struck some years ago with the optimism of my non-scientific friends as regards our future, I suggested that a committee of the British Science Guild should b'l formed to investigate. our available sources of energy. This Guild is an organization, founded by Sir Norman Lockyer, after his tenure of the presidency of this association, for the purpose of endeavoring to impress on our people and their government the necessity of viewing problems affecting the race and the State from the standpoint of science; and the definition of science in this as in other connections, is simply the acquisition of knowledge, and orderly reasoning on experience already gained, and on experiments capable of being carried out, so as to forecast and control the course of events; and, if possible, to apply this knowledge to the. benefit of the human race. The Science Guild has enlisted the services of a number of men, each eminent in his own department, and each has now reported on the particular source of energy of which he has special knowledge. Besides considering the uses of coal and its products. and how they may be more economically employed, in which branches the Hon. Sir Charles Parsons, Mr. Dugald Clerk, Sir Bov- erton Redwood, Dr. Beilby, Dr. Hele-Shaw, Prof. Vivian Lewes and others have furnished reports, the following sources of energy have been brought under review: The possibility of utilizing the tides; the internal heat of the earth; the winds; solar heat; water- power; the extension of forests, and the use of wood and peat as fuels; and lastly, the possibility of controlling the undoubted but almost infinitely slow disintegration of the elements, with the view of utilizing their stored-up energy. Suffice it to say that the Hen. R. J. Strutt has shown that in this country at least it would be impracticable to attempt to utilize terrestrial heat from boreholes; others have deduced that the tides, the winds, and waterpower small supplies of energy are no doubt obtainable, but that, in comparison with that derived from the combustion of coal, they are negligible; nothing is to be. hoped for from the direct utilization of solar heat in this temperate and uncertain climate; and it would be folly to consider seriously a possible supply of energy in a conceivable acceleration of the liberation of energy by atomic change. It looks utterly improbable, too, that we shall ever be able to utilize the energy due to the revolution of the earth on her axis, or to her proper motion round the sun. Attention should undoubtedly be paid to forestry, and to the utilization of our stores of peat. On the Continent, the forests are largely the property of the State; it is unreasonable, especially in these latter days of uncertain tenure of property, to expect any private owner of land to invest money in schemes which would at best only benefit his descendants, but which, under our present trend of legislation, do not promise even that remote return. Our neighbors and rivals, Germany and France, spend annually £2,200,000 on the conservation and utilization of their forests; the net return is £6,000,000. There is no doubt that we could imitate them with advantage.

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