摘要:

THE head of a social research department, -L such as exist on tlu3filjfejirside of the Atlantic, who was on the ouUoolrioi1 a subject for o&student's thesis, might dcffjvorse thaft-SHgasstf toe modern conferenofe turning as suitable for investigation. Attendaltee'at conferences and congresses threatens to consume an increasing proportion of the lifetime of scientific workers. If the laborious method of investigation which finds favour in certain places was followed in the department, we may suppose that the student would classify the motives for organising conferences and the methods of procedure followed, and would finally attempt to correlate different procedures with the ' results ' attained. Such a student might find it difficult to fit the recent World Population Conference at Geneva into any well-defined category. On one hand, the programme was limited to the strictly scientific discussion of certain aspects of the population problem. On the other hand, it is probably correct to say that in the minds of most of those who attended was the conviction that the regulation of the quantity, quality, and distribution of population is a world problem which the organised communities of the world have to face at no distant date. It was a conference of biologists, statisticians, and economists, who did not trespass into the province of the politicians, but for the most part realised keenly the need for an agreed international policy if ordered progress is to be secured. The problem of migration was discussed at the conference, and it is in connexion with the difficulties arising from migration that the politician is first called upon to deal with practical population problems. It is only within the last few years, owing to the admirable work of the International Labour Office, that trustworthy and comprehensive statistics of migration have become available. These deserve careful analysis and discussion, which should be of practical use. But it may prove to be true that, once the forces leading to a desire for migration have been generated, it is beyond the skill of statesmen, however well informed and well intentioned they may be, to arrange a peaceful solution of the problem. It is necessary, therefore, to inquire into the nature of these forces in the hope that civilised nations may attempt to control them. Since migration is a most complex phenomenon, we are led to study the more fundamental aspects of the whole question, all of which bear upon migration. These are such as the biological problems of fertility, the economic problems of optimum density, and the social problems of family limitation. The hope is that civilised nations will learn in time to found their internal policies upon such knowledge as may be accumulated upon these-matters. In this way maladjustments may be avoided before their results coalesce and manifest themselves in the form of pressure to migrate. This they will only do if they realise that in the end national well-being coincides with international well-being.This programme sounds sufficiently chimerical, even though we have limited it to civilised States. There can be little doubt, however, that a common action by civilised States is urgent. United upon a population policy, they may be able to maintain world order in face of developments in Asia which seem inevitable. We now know, thanks to the recently published researches of economic historians, the true story of the great outpouring of population in the western world during the last century. It was due not to an increase in the birth-rate, but to a decrease in the death-rate. In all likelihood events in the East will follow the same course. Indeed, in India events arc now taking this turn. Since we cannot anticipate that any effective efforts will be made to guide events in the East so as to avoid the otherwise inevitable pressure towards migration, the only hope lies in a western world united in a common policy based upon a common basis of scientific investigation, and thus strong enough to control the situation. If, on the other hand, the so-called civilised States embark upon competitions in numbers, they may well come to grief, quite apart from the fact that the eastern races will inevitably beat them at the game. It is a commonplace remark that the value of scientific conferences lies in the opportunities of personal contact, and not in the formal communications or discussions. It is only the readers of the popular press who imagine that great discoveries are announced at congresses. This is not quite as true of the social sciences as of the natural sciences. The mechanism for distributing the results of research work in the natural sciences seems to be in advance of that in the field of the social sciences. It was interesting to observe that when biological matters were under discussion, the results of recent research were more generally familiar than when social phenomena took the first place on the programme. Apart from the value of contact and of disseminating information oil certain matters, the conference has achieved a distinct success in that it has decided to set up the nucleus of a permanent organisation for the study of population problems. It cannot yet be said what form this will take. But if out of it grows an organisation of a truly international character, with the prestige of the full support of the representatives of the relevant sciences behind it, the conference will stand out as a notable event. The habit of international consultation on the scientific aspect will grow, and this cannot fail in time to influence international policy.The function of a permanent international organisation might thus be twofold. The greater the prestige it gains, the more unlikely will it be that international policy will be directed regardless of the findings of biologists and economists. It would not be a propaganda organisation except in the sense that it would assist to disseminate facts. Again, a most useful piece of work lies in the correlation of investigations in different fields. The practical problems of population arc complex problems. The biologist, the statistician, and the economist all have, for example, something to contribute towards the solution of the problem of migration. A deliberate effort is, however, required in order to give due weight to the various contributions in such a fashion that practical policies have regard to all the more important factors involved. It was evident enough at the conference that workers in different fields who have become interested in practical problems look at these problems only too often from a very narrow angle. An international organisation might do good work in opening the eyes of specialists to the necessity of taking the results, of workers in other fields into account before they deliver their opinions as experts upon problems which they have not fully envisaged. So far as it affects Great Britain, one aspect of the present situation, which is not without its importance, deserves a word of comment. It is not to be supposed that population problems, when discussed at conferences or elsewhere will be referred to in the popular press unless they can be dressed up to justify a good headline or to form a sensational paragraph. But it is disappointing, to notice that the more responsible organs in Great Britain appear to be committed more or less to a boycott of these matters. The reference is not to this conference in particular so much as to events here during the last few years. We have still a long way to travel towards a rational policy when editors of responsible papers regard popula tion problemsas too indelicate or too dangerous, for discussion in their pages.

ISSN:0028-0836    

DOI:10.1038/120465a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE writer of a ' comprehensive treatise ' is in grave danger of being drowned by the torrent of information which flows in upon him as soon as h'e accepts the responsibility of taking cognisance of all the details of his chosen subject. It is almost a commonplace that the amount of readable matter in such a treatise (like the pressure of a gas) is inversely proportional to its volume. On this basis of calculation, it might be expected that a treatise on chemistry which has only reached Group IV. of the Periodic Classification in a seventh volume of 1000 pages would be intolerable in its dullness. It is therefore a welcome relief to find that the opening sentence of Dr. Mellor's new volume has the arresting character which one might expect to find at the beginning of a detective story. "In 1791, W. Gregor studied the black sands of Menacan, near Falmouth, Cornwall, and found some greyish-black granules which were attracted by a magnet." The sleuth then sets to work to solve his riddle with the help of hydrochloric and sulphuric acids, ammonia and potash-lye, and finally brings in tincture of galls as a means of checking a possible alibi, and ends by confiding -to Crell's Chemical Journal instead of to his friend Watson-his conclusion in the following terms: " The extraordinary properties of the sand have led me to believe that it contains a new metallic substance. In order to distinguish this substance from others, I have ventured to suggest a name derived from the neighbourhood-Menacan, Cornwall-where it was found, and therefore I propose to call the metal menacanite."If the narrative lacks the element of horror, which is such an asset to the writer of detective stories, it has at least the merit of taking us to the romantic west, to speculate whether the hero of the story saw the fig-tree growing out of the side of the church tower when he visited Menacan at the time of the French Revolution, whether he had a magnet in his pocket whilst he was reading in the church the message of Charles I. to his loyal Cornish subjects, and, finally, in what precise locality he discovered the magnetic granules. After reading in the succeeding sentences how the new element was robbed of its Cornish name and called ' titanium,' one is impelled to breathe a lament, such as Urbain must have uttered when ' celtium ' was re-baptized as ' hafnium.' Since the volume deals with all the elements of Group IV., except carbon and silicon, the reader will turn with interest to Chap, xliii. to see what the author has to say about the celtium-hafnium controversy, on which readers of NATURE should be already well-informed (see vol. Ill, pp. 79,182, 252, and 462). The verdict of our modern Berzelius is unequivocal:-" In 1911, G. Urbain announced the discovery of a new element in some residues remaining after the separation of the lutecium-ytterbium fractions of the rare earths. He called it celtium. Subsequent observations showed that all the evidence in favour of this element was worthless. In May, 1922, A. Dauvillier found that the X-ray spectrum of these residues was in agreement with the presence of an element, atomic number 72, and G. Urbain applied the old term to the new element. The neo-celtium was not obtained in sufficient quantity, or sufficiently purified, to enable any other unequivocal statement to be made of its properties. Meanwhile, January 1923, D. Coster and G. von Hevesy reported a new element. . . . The new element was called hafnium, Hf-from Hafnia, an ancient name for Copenhagen." After reading these remarks it is not surprising to find that the chapter is labelled ' hafnium ' and not ' celtium.'The remaining elements of the first sub-group are zirconium and thorium, the latter being of interest both on account of its radioactivity and of its technical use in the ' incandescent gas-mantle.' These two topics form the subject of two sections in which the relevant researches are adequately reviewed. Passing on to the other, sub-group, we find a section on " The Physical Properties of Tin " which is effectively illustrated by photographs of slip-bands in strained tin and of the surface of a sample of tin affected by the ' tin-pest.'Under the heading " Physiological Action of Lead " an amazing story is told of a custom, which appears to have prevailed for many centuries, of " rendering harsh wine milder " by boiling it in lead vessels, or by the action of litharge. The litharge or white-lead was singularly efficacious in renovating spoilt wine, but its physiological effect was disastrous, producing, " according to the constitution of the consumer, a speedy or a lingering death, violent colics, obstructions, and other maladies." It was, however, so successful, from the point of view of the vendor, that its use could barely be stopped by the severest of punishments, torture and death. After this, it is difficult to admit that the use of preservatives in food is a purely modern vice, since it no longer seems necessary to suggest the infliction of penalties such as these merely iri order to prevent the addition of boric acid (not exceeding 0-4 per cent.) to cream, or of bcnzoic acid to that form of coffee which is sold in a bottle instead of a tin. The final chapter of the volume deals with the " Inert Gases." This chapter relapses, perhaps inevitably, into the form of a catalogue of numerical data, alternating with long lists of authorities on a subject which lias interested many workers both in physics and in chemistry. The reviewer has, however, formed the opinion that Dr. Mellor writes with more freedom and in a more interesting style as he ' warms up ' to his colossal task; and the numerous illustrations, although generally reproduced on a very small scale, are of great value in setting out the precise conditions of equilibrium in scores of different systems. The photographs, which are not reduced so drastically, provide another welcome relief to the solidity of the text; and tiny diagrams, representing the results of X-ray analysis of substances such as stannic iodide and the chlorostannates, show how closely the author has kept up with modern developments. He may therefore be congratulated without reserve on having arrived at his half-way house without showing any signs of weariness or nagging, since he appears to be even more fresh and vigorous now than when he first started out on his long journey.

ISSN:0028-0836    

DOI:10.1038/120467a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

IN the ordinary progress of knowledge, men come and men go, each contributing according to the talents given to him, but from time to time there appears ail individual whose work signals the beginning of a new era. Such a man does not merely add his own quota to the growing stream of knowledge, but seems, by some hidden power, to unlock the waters of the well of truth so that the stream becomes a flood. Such a man was Lister, whose centenary is celebrated this year, and such, too, was Manson, who stands in the same relation to modern tropical medicine as Lister does to modern surgery. It can but add to Lister's fame that the recently published " Life and Work of Sir Patrick Manson " makes known the part that Lister played in support of Manson and Ross in their pioneer work. Manson's contributions to scientific knowledge are as well known as they were varied. A list of his published papers occupies twelve pages. He has been called ' Mosquito Manson.' It is true that his demonstration of the r61e of mosquitoes in relation to parasitic disease in man is the brightest single gem in his crown of achievement, but attention has been focussed too much on this one discovery. Much more than that underlay Blanchard's naming him " the father of the modern science of tropical medicine." It is fitting that the full measure of Manson's worth should be laid before the world by two men so intimately connected with him both in work and private life as Dr. Manson - Bahr and Col. Alcock. What impresses, in this record, is the bigness of the man. Here was no dry-as-dust scientist content with making additions to abstract knowledge. In professional life he was a surgeon of skill and repute-and the two do not always go together- a physician of insight and mature judgment, an obstetrician whose ability and tact made him acceptable to a foreign and highly conservative race, a teacher who could attract and hold his pupils, a laboratory worker whose dexterity overcame the difficulties of place and circumstance; and his work in every sphere was illuminated by an inquiring genius which set him ever speculating, probing, searching, until basic facts and processes were laid bare. In the world of affairs he was shrewd and penetrating, with organising power and driving force which made him the effective adviser of a great department of State, and to which there remain as monuments the medical school of Hong Kong and the London School of Tropical Medicine. Of his private life too little is known, and even his biographers are compelled to sketch with uncertain pen the twenty years and more of Manson's life which were spent abroad. He was good company, kindly and courteous; tolerant of another's contrary opinion so long as it was sincerely held; a great reader, passionately fond of poetry; no mean geologist; a good man with a gun, and an angler after the heart of Isaac Walton.Born in Aberdeeiishirc in 1844, Manson was at first destined to be an engineer. His youthful desire to learn ' how the wheels go round ' is seen when we find him, as a schoolboy, dissecting a cat. Perhaps this early anatomical study, as much as some physical frailty, turned his attention from the crude mechanisms of man's construction to the most delicate machine of all, man himself. It may be, too, that the accident of the cat's containing a tapeworm determined his lifelong interest in the helminth parasites of man. Graduating in medicine at Aberdeen, he soon went abroad, settling first at Amoy and later in Hong Kong. Some idea of the difficulties to be overcome may be gathered from his having had to run for his life when attempting to perform an autopsy, and from the fact that the Customs Gazette was for long his only medium of publication. His independence of character is seen in his repayment to his father, with the first-fruits of his labour, of the expenses of his medical education. Manson was liked and respected by the Chinese, and himself grew fond of them, a point brought out by Dr. H. M. Hanschell in an admirable pen portrait quoted by the authors. In Hanson's experiences on his first return to England is found the key to his determined and successful efforts to establish definite teaching on the diseases peculiar to hot climates. Impressed as he had been with his own ignorance of such subjects, he set about to acquire the fullest knowledge to be obtained in London. He found nothing save what he extracted for himself by searching the library of the British Museum. Many pages of the " Life " are taken up by an extremely interesting series of letters from Manson to Ross, written while the latter was working to establish the mosquito-malaria theory. This part of the book makes a vivid picture-as vivid as and truer than that painted in highly-coloured language by a recent writer in the New World: Ross in India labouring under difficulties, now making a little progress, now becoming sidetracked, now disheartened, now hopeful again as some success crowned his efforts; and Manson in London anxiously awaiting every mail, writing frequently with helpful suggestions, supporting in high places by all the influence he could wield or induce others to wield, encouraging to solve the problem before other investigators should succeed, and reiterating, with a constancy which Ross might be pardoned for finding tiresome, his advice to " follow the flagellum." The outcome is known to all. Failing with the other mosquitoes, Ross succeeded with the dappled anopheles and was able to go a stage further than did Manson's hypothesis, and to show how the man-mosquito-man cycle is completed by the mosquito in the act of biting.The account of Manson's work for the Chinese in Amoy and Hong Kong should be read by the many in China and the few in Great Britain who represent at present that the British in China have played no part save that of self-interest. Britain's history teems with the names of her sons who have gone to strange lands and have there enhanced the prestige of their race, and none more nobly than did Manson. Though much of his life was spent outside the Empire and much in a colony territorially insignificant, yet he may with truth be called an Empire builder. Directly through his instrumentality, more than three thousand doctors have received expert training in those special arts and sciences without the exercise of which many of the British Empire's resources could never be tapped. His fame, like the influence of his life and work, is world-wide and abiding. 1 The motto of the Royal Society of Tropical Medicine and Hygiene, of Which Manson was first, president.

ISSN:0028-0836    

DOI:10.1038/120468a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

MR. LYNCH covers a wide ground in his book on science dealing successively with mathematics, physics, chemistry, biology, physiology, medicine, psychology, and ethics. The modern sciences are so highly developed and specialised that it is unusual for a single writer to be able to discuss competently the technical details of more than a few sciences. Mr. Lynch considers that this tendency to specialisation requires correction, and with a laudable courage he attempts to put his principles into practice, mastering at the same time the technicalities of each science and explaining them in language which is intelligible to all. While, however, his book contains a great deal of scientific matter, its central theme does not appear to be so much the particular discoveries or the development of science as a criticism of current views as to the basic principles and methods of science. It is this philosophical theme which gives unity to what is otherwise a series of discursive essays. Mr. Lynch contends that the ordinary view or assumption as to the absolute certainty of scientific knowledge is mistaken, and he professes to establish his claim by recounting the constant mistakes committed by the great men of science of the past. The soundness of such an argument may be open to question, but the historical account given of science is often lively and interesting, although perhaps too much is made of the small mistakes, and foibles of great men. When Mr. Lynch comes to philosophers such as Kant, he paints a picture which is clearly too one-sided to carry much conviction. He does not set out in this book to explain, at any length his own theory as to the character of scientific certainty, but he is content to indicate a view somewhat similar to that of Mach and to refer the reader to his work on psychology for a more complete exposition.In his first essay Mr. Lynch reviews briefly the early period when the philosophers were also the leading scientific workers. Actuated by a praiseworthy desire to make the speculations of these early thinkers live, he tends to modernise overmuch their doctrines; thus he says that in Herachtus we find the early apprehension of the principle of evolution and also the theory of ether; moreover, he scarcely does justice to the metaphysics either of Plato or of Aristotle. According to Mr. Lynch, the subject which Plato pursued with the greatest tenacity was mathematics, but the medieval schoolmen seized upon the more obscure of Plato's doctrines and " left their malign influence to obfuscate the brains of many of our most famous and authoritative thinkers of to-day "; and while Aristotle's " Ethics " is " a work of marvellous creation," Aristotle was nevertheless not strong in the " field of psychological analysis." If Mr. Lynch takes a ' rationalist ' view of medieval Platonism and is also hostile to modern absolute idealism, he is equally sceptical both of the scientific and of the philosophical theories of relativism. If his chapters on relativity have been understood aright, he thinks that Einstein has added very little to the body of scientific knowledge, and that his theory is rather a convenient formula liable to be overturned to-morrow, than a statement of an abiding truth. Philosophical relativists, such as Lord Haldane, Mr. Lynch states have taken Polonius as their model and cannot be regarded seriously. Apparently the cure for all these fallacies and the basis for a true system of science and philosophy is to be found in a new constructive psychology.In the latter part of his book Mr. Lynch reviews modem schools of thought, and he does not conceal his contempt for most of the leading thinkers. Bradley, Bergson, Bosanquet, the Earl of Balfour, Dean Inge, Dr. Schiller, Prof. Wildon Carr, Prof. Dawes Hicks, and others, are dismissed with none too complimentary remarks, and for universities and scientific associations generally Mr. Lynch has scarcely a good word to say. He appeals over the heads of the professors to the great public, but he should bear in mind that while the public always likes and admires outspoken criticism, witty or caustic as the case may be, it immediately turns a deaf ear if it suspects a personal grudge or ill temper.

ISSN:0028-0836    

DOI:10.1038/120469a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

LIFE aiycT its incidents are always changing, new fashions and phenomena come and go, and among these our diseases alter not only in name but also in nature. With the more rapid means of communication the rate of living, though not longevity, has increased, and, like most generations, the present complacently condoles with itself on the increased strain of modern life. Neurology has made enormous advances in recent years, and, as a result, many new diseases have become recognised, but apart from the influence of this addition to knowledge there appears to be an increasing susceptibility of the central nervous system to attacks of epidemic disease, such as acute poliomyelitis during this century, during the special conditions-1 of the War cerebrospinal fever, and since the later years of the War a practically new disease, epidemic or lethargic encephalitis, known in the lay press as ' sleepy sickness,' which should be distinguished from the sleeping sickness of more tropical climates, due to infection with trypano-somcs. The endowed lectures at medical institutions offer an opportunity for the publication of original investigations and for surveys of current knowledge. The appearance in an expanded form, with more recent additions, of the scholarly Milroy Lectures on " Epidemic Diseases of the Central Nervous System," given in 1925 before the Royal College of Physicians of London by Dr. A. Salusbury MacNalty, of the Ministry of Health, and dedicated to his former teacher, the president of the College, Sir John Rose Bradford, provides convincing proof of the value of such endowments. Dr. MacNalty had much to do with the early investigation of encephalitis lethargica, first described early in 1917 by Economo and von Wiesner in Vienna, and attracting attention a year later in England, where it was first suggested to be botulism, a very rare disease in Great Britain, of which the only definite outbreak occurred in 1922 at Loch Maree from eating infected potted duck paste.Well equipped in epidemiology, Dr. MacNalty is therefore able to give an admirable account of the epidemic nature and history of the three diseases - acute poliomyelitis and polioencephalitis, cerebro-spinal fever, and encephalitis lethargica - not only in man but also of what is known about their occurrence in animals. Since the end of the War the incidence of cerebrospinal fever has greatly diminished, but unfortunately the reverse applies to the other two, both of which are due to infection with an ultra-microscopic virus spread by healthy ' carriers/ The after-effects of encephalitis lethargica on the brain, which may follow acute attacks so slight as to pass almost or quite unnoticed, are calamitous; when the incidence of abortive attacks and of its form, or the closely allied condition, known as epidemic hiccup, which do not appear in the notification returns, are taken into account, the increase becomes positively alarming. A thorough knowledge of the causation and epidemiology of these diseases is most important in providing efficient means for their prevention, a subject on which Dr. MacNalty also touches, and hence this well -written and detailed account of their epidemiology is most appropriate.

ISSN:0028-0836    

DOI:10.1038/120470a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE third instalment of the work edited by Prof. Gutenberg maintains the standard of the first two. It begins with a clear and up-to-date account of terrestrial magnetism by Dr. J. Bartels. One learns in it that the whole energy of the earth's permanent magnetic field is equivalent to that of the radiation received from the sun in three seconds ! - or, it maybe remarked, to the gravitational energy released by a radial contraction of the order of 10 ~8 cm. Prof. Gutenberg then devotes sixty-six pages to the physical constitution, figure, density, and thermal state of the earth. In a useful, if brief, account of the figure of the earth, the Badau approximation is given, but neither Darwin nor Callandreau is mentioned. Present knowledge of the distribution of density is well summarized. The three physical states of matter are clearly defined on p. 455. The distinguishing mark of a gas is its high compressibility, while a solid is distinguished from a liquid by the possession of a measurable rigidity, or elasticity of form, which liquids have not. Glasses are therefore regarded as solids, and not as liquids. But Gutenberg seems to contemplate seriously the possibility that all solids have a finite viscosity; the proposition is perhaps worth consideration, though neither experiment nor theory lends it much support. The work of Bridgman, Tainmann, and others on the properties of matter at high temperatures and pressures is described. Methods of measuring gravity and its variations with position are treated fully by Prof. Ansel, with special reference to the detection of masses of abnormal density near the surface. An account of electrie currents in the crust is then given by Bartels.The last chapter, by Gutenberg, deals with the application of seismological methods to the investigation of the uppermost layers of the crust. Until recently seismology, so far as it has dealt with the sedimentary layer at all, has usually regarded it mainly as a nuisance. But the problems it involves are now being attacked, and this chapter is, I believe, the first connected account of the results. Artificial shocks, such as explosions or even the fall of a heavy body, are recorded on instruments with magnifications of the order of a million, so that movements of almost molecular extent can be detected. The sound wave in the air is a prominent feature of the records. The velocities of compressional waves in the sedimentary rocks are notably less than in igneous ones, of the order of 2 km./sec. as against 5-4 km. to 8 km./sec. Distortional waves have hitherto been found more difficult to observe.

ISSN:0028-0836    

DOI:10.1038/120471a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE author, holding that a proper understanding of the relation of germplasm to soma is a prerequisite in the investigation of all problems of biology, has set himself the task of giving in broad review an account of the established facts concerning this relationship as it exists in the animal kingdom (including man). The result of his endeavour is this excellent and most useful book. The objective method of presentation, the historical review followed by a fair statement of modern opinion, the judicial comparison of opposing doctrines, the avoidance of any exhibition of preference save only in those matters upon which the author is a recognised authority, make the reading of this book both pleasant and profitable. The subject of the endocrine activity of the gonads ia treated in a most thorough manner, and any one who seeks trustworthy guidance in the Steinach-Stieve controversy will find it here. Castration, gonad implantation, substitution therapy, and rejuvenation are discussed fully, and the r61e of the nervous system in the maintenance of the sexual characters is examined by reference to the author's well-known work concerning the thumb-pad of the frog. The bibliography does not include all the names and papers to which reference is made in the text.This work, into which Harms's earlier book is worked in (" Die innere Sekretion der Keimdriisen," Jena, 1914), can be, warmly recommended. Not the least of its good qualities is that the author indicates everywhere lines of profitable research.

ISSN:0028-0836    

DOI:10.1038/120472b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

EVIDENCE was presented (B. Lewis and E. K. Rideal,J. Chem. Soc.,129, 583 and 596; 1926) for the view that the photo-expansion of bromine and other halogens in the presence of water vapour (Budde effect) is due to heat liberated by the recombination of halogen atoms set free by the absorption of light quanta. Although absorption of radiation occurs in the dry gas, no Budde effect is observable (J. W. Mellor,J. Chem. Soc.,81, 1280; 1902; Lewis and Rideal,loc. cit.) even when the gas is subjected to an intense source of ultra-violet radiation (E. B. Ludlam,Proc. Roy. Soc. Edinburgh.44, 197; 1924). This is interpreted to mean that the halogen does not dissociate in the dry state; that the radiation absorbed activates the halogen molecule for a short period of time and is then emitted (presumably as longer wavelengths).It has been shown by several workers that the photo-chemical union of hydrogen and chlorine does not proceed in visible radiation in the absence of water vapour. Of the numerous mechanisms proposed for this reaction, the Nernst atomic chain still remains on the whole the most plausible. The formation of hydrogen bromide from the elements is known to proceed by way of bromine atoms, tho erido-thermicity of one of the atomic steps preventing long chains (for literature see Lewis and Rideal, J. Amer. Ghem. Soc., 48, 2553; 1926). Lewis and Rideal (J. Amer. Che,m. Soc,., loc. cit.) have shown that the absence of water vapour retards this reaction. La,ek of space prevents adequate reply to Bodenstein and Jost (J. Amer. Chem. Soc., 49, 1416; 1927), but it should be mentioned that Table TIL, p. 2558 of Lewis and Ridoal's paper, presents a series of experiments on the formation of hydrogen bromide in as dry a system as was possible at the high temperatures without the use of phosphorus pentoxide, in which considerable retardation was observed, and in one ca,se, nearly stopped completely. Two or three typographical errors prevail; the values for experiments 8 and 11 should read 45-8 per cent, and 56 per cent., ami in the last column 52-2 per cent, belongs to experiment 10. It is generally agreed that the high quantum yield in the photo-synthesis of hydrogen chloride is due to some chain mechanism involving chloride atoms. Since the mechanism of the Budde effect is probably the primary step in this reaction (BernaTcl Lewis, Trans. Ji'ar. Sue., 21, 585; 1926), and if the atoms which initiate the chains are absent, then it follows that the latter cannot be initiated in the absence of water vapour. There seems to be no evidence that water vapour functions in the chain itself as wa,s proposed by Coehn and Jung (Bur. 56, 696; 1923) and Coehn and Heymer (Die 'Naturwissenschaflen, 14, 299; 1926) from the observation that the dry gases did not combine in the visible but did so in the ultraviolet. For the purpose of brief discussion these two mechanisms will be reproduced here.A. Moist hydrogen and chlorine: in visible light. (1) ci2 + iiK (small)=cra (2) C1'2 + C12 -Cl2 + 2 Cl (3) Cl i H2O =IT01 + OH (5)H + C122 = HC1 + CI B. Dry hvdrogen and chlorine: in ultra-violet. (1) 01 s I hv (large) =C1"2 (2) C1"2 + C12 = 012 [ 2 01 (3) C1"2 + H2 _012 + 2 H twice (4) H + C13 = HC1 + Cl (5) 01 +01 =ClaReaction (2) in both mechanisms is unnecessary, since we know that non-polar (Franck, Trans, tfar. Soc., 21, 536; 1926) and pola,r (TConclratjew, Z. /. Physik, 39, 191; 1926; Bernard Lewis,' NATUBE, 119, 493; 1927) molecules undergo optical dissociation in a single act without collision. It has been pointed out that tho time between absorption and dissociation for these simple molecules must be shorter than 10"lu sec. (Bernard Lewis, Proc. Nat. Acad. Sci., in press). If atoms can be formed in tho dry gas, then since (1) and (2) in B are confined to one step without collision, the dissociation of the halogen would have occurred before (3) could ta,ke place. At lower hydrogen pressures the quantum yield would be less than one. If we agree that (2) does take place in the dry gas, then in a 1: 1 mixture of hydrogen and chlorine (2) may occur more often than (3), due to tho smaller heat of dissociation, and the quantum yield would again be less than one. Altering the relative concentrations would also affect the yield. It is difficult to see why chlorine atoms resulting from (2) and (4) in B cannot propagate chains as in Cl + H2=HC1 + H, for this reaction still remains thermodynamically possible from la-tost thormochomica-1 data. In this case chains, and therefore high quantum yields, would be expected. Mechanism B, for the dry gases, cannot explain satisfactorily the theoretically predicted quantum yield of two which was in general realised by Coebn and TToymer. The chain mechanism in A for the moist gases is. extremely doubtful. Considerable doubt has been cast on (3) by Norrish (Trans. Far. Soc., 21, 575; 1926). Thon (Fortschritt d. c.he.m. Phys., 18, 60-67; 1926), after certain considerations, concludes with Lewis and Rideal (J. Am. Chem. Sue., loc. cit.) that the action of water is physical and therefore does not enter into the chain mechanism.It can be shown approximately that reaction (4) in A is ondothermic to such an extent that the small efficiency of fruitful collisions between OH and Jti2 would cut the chains very short. Thus an essential step in the chain is not always effective, if indeed it is at all, and the mechanism therefore is inadmissible. Until evidence to the contrary is available, the mechanism of the moist reaction must be considered as a primary dissociation of the halogen under the influence of water vapour followed by an atomic chain, either that of .Nernst or one suggested by Thon (Z. phys. Ohem., 124, 327; 1926), The dry reaction is most simply explained by activation of a chlorine molecule and its interaction with hydrogen molecules to form two molecules of hydrogen chloride. However, Thon (toe. cit., p. 69) suggests that a trace of oxygen in Coehn and Heyrner's experiments would bring about the photo-synthesis of water in ultraviolet light and the main reaction could proceed. This could be tested by exposing a dry mixture to visible light after the reaction had just commenced by exposure to ultra-violet. If this reasoning is correct, the mixture should now react in the visible.There is a, possible method of testing directly whether water vapour functions in the chain mechanism. Porter, Bardweli, and Lind (J. Am. Chem. (S'oc., 48, 2603; 1926), in some important experiments on the synthesis of hydrogen chloride, have shown that tho chains are of the same length whether the reaction is carried out photochemically or by means of alpha radiation. Since the variation, of sensitivity of the mixture produces the seme change in rate of both reactions, they conclude that " this must mean that the reaction chains in both cases are of equal length, and hence the mechanisms of the secondary reactions are identical whatever they may be." Tonisation by alpha radiation always takes place, and thus the initiators of the chains are present regardless of water vapour. If water plays a role in the chain mechanism, no chains should be propagated when a dry mixture of hydrogen and chlorine is. exposed to alpha radiation. On tho other hand, if chains, and therefore high quantum yields, persist in the absence of water vapour, this would indicate that the latter does not function in the reaction chains. It is intended to carry out these experiments.

ISSN:0028-0836    

DOI:10.1038/120473b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

SINCE the publication of my letter on the transmutation of lead in NATURE of May 1, 1926, I have continued the experiments in collaboration with Dr. A. Karssen and W. A. Frederikse. In the letter mentioned above I stated that our repeated experiments showed that the phenomena observed with the quartz-lead lamp and pointing to a transmutation of lead into mercury, were very difficult to reproduce. The lamp with which we obtained the photograms published was the tenth made after changing the construction from time to time to secure the most distinct results. In the hope of arriving at a still better method, and intending to distil off the mercury continually during the sparking process, the construction of the lamp was again changed. The result, however, was that, even without distillation, the lead spectrum now remained absolutely free from mercury lines.After this very unexpected result, a lamp was constructed as nearly identical as possible with the lamp before the last modification was made. The behaviour of this new lamp was not quite the same as that of the old one; the discharges were different, the last contact was not made by a very thin jet of lead, and by oscillation all the gas was pumped out of the sparking space, which did not take place with the old lamp. Notwithstanding this, the appearance of mercury lines was again observed, but not so strong, and after much longer periods than before. From this we obtained the impression that the kind of discharge, being influenced by the construction of the lamp, was important here. To find another easily reproducible method, we tried now another construction -which allowed sparking at high voltages, 160,000 volts and 10 milliamperes in a nitrogen atmosphere at different pressures between two solid lead electrodes, but the lead spectrum remained absolutely free from mercury lines. Experiments of the same kind were carried out with a lamp in which the lead electrodes were heated above the melting point, but the results of all these experiments with long sparks and consequently with discharges of relatively small potential fall, gave only negative results.In the meantime, as mentioned in another paper, we applied a different sparking method, using carbon disulphide as liquid dielectric. From the extra pure lead supplied by Kahlbaum, and treated by us in the way already described to remove every trace of mercury, two electrodes, 15 mm. thick and 2 cm. long, were made. These were mounted in two holders of steel, connected to two rods of steel, and all the steel parts were heated beforehand for twenty-four hours in an electric furnace at about 800° in an atmosphere of pure nitrogen. The steel-holders and rods treated in this way, and also the lead electrodes, were examined by the slightly altered method of Stock (Z. f. anorg. Chem., 39, 465 and 791; 1926) and appeared to be completely free from mercury. Since it was possible that, for purification, the carbon disulphide had been shaken with mercury, sulphur was added and the solution was boiled for two hours in a flask with a reflux-condenser. The solution was then distilled, and 200 c.c. of the distillate was examined. No trace of mercury was found, whilst a quantity of 0-001 ingm. mercury would have been detected easily. Now we started our definite sparking experiments at 160,000 volts and 10-20 milliamperes. Since we wished to work at this voltage, and the dispersed lead soon diminishes, the electrical resistance of the dielectric, causing a decrease of the tension, every time, as the voltage began to decrease, the experiment was stopped until the dispersed lead had precipitated. After having sparked in this way discontinuously for one or two hours, the dispersed lead was gathered and examined. In 30 gm. of the mixture of dispersed lead and carbon, 0-1-0-2 mgrri. mere ury was found. The same result was obtained six separate times. Then our transformer went wrong, and it was some time before we could continue our experiments.In the meantime I resolved to carry out an experiment, the results of which would be very convincing. It would be very important if it could be proved in repeating the experiment, after replacing only the lead electrodes by electrodes of another pure metal, of which no transmutation into mercury could be suspected, that the dispersed metal in this case is always free from mercury. I chose platinum; two platinum rods, 3 mm. thick and 4 cm. long, wore mounted in the same steel-holders and the sparking experiments were repeated. The result was that the conglomerate of dispersed platinum and carbon was found to be free from mercury. On repeating this experiment, the result was the same; and the conclusion consequently was, that the mercury found in our sparking experiment with lead electrodes must have been formed from lead. I intended to send now a preparation of our mercury to Dr. Aston, whom I had asked to examine it in his mass spectrograph, but I preferred not to do so before we had repeated the platinum experiments several times. The third sparking experiment with platinum electrodes and with a new quantity of purified carbon disulphide gave, however, not a negative but a positive result, but not so strong as we found in our experiments with lead electrodes.Taking for the fourth experiment the carbon disulphide previously used in our third experiment, the result was again negative. From this it follows that the new quantity of carbon disulphide must have contained a trace of a mercury compound, probably a volatile organic one, which was not removed by the purification method applied, and it had escaped detection. Since the positive result, after sparking with platinum electrodes, had disappeared, it seemed that this mercury compound could be dissociated and removed by strong electrical discharges, and therefore wo resolved to purify the carbon disulphide in future by the sparking method with platinum electrodes. The result of this method was excellent. After having sparked 750 c.c. of carbon disulphide for 1J hours, the conglomerate of dispersed platinum and carbon was separated from the liquid, and the liquid was distilled. The distillate proved to be free from mercury. This was found not only by direct chemical analytical examination, but also by submitting the carbon disulphide to a repeated sparking process between platinum electrodes, and by examination of the conglomerate of platinum and carbon formed-about 7 grams. The conglomerate was now completely free from mercury. This carbon disulphide purified by electrical discharges was used in our next experiments with lead electrodes, 1 cm. thick and 3 cm. long. These experiments, repeated several times, have so far given only negative results. At the moment I am, therefore, inclined to conclude that the mercury found in our earlier sparking experiments came, certainly partly and perhaps entirely, from the carbon disulphide. This seems possible, since in these experiments a used quantity of carbon disulphide was supplemented by a new quantity of carbon disulphide purified in the ordinary way. But there is still this difficulty, that after sparking between the lead electrodes in carbon disulphide, purified in the usual way, the reaction was stronger positive than after sparking in this dielectric between platinum electrodes, in the same circumstances as regards voltage, current strength, and time. Consequently, there is still an uncertainty, which probably will be solved by our continued investigations. Though the experiments, which have been mentioned here very shortly, have taken a full year, they are only the beginning of detailed investigations in different directions. Still, I feel obliged to make this communication, since I know that other investigators are repeating our sparking experiments with carbon disulphide

ISSN:0028-0836    

DOI:10.1038/120475a0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature

摘要:

THE observations described in the striking experiment of Hubbard and Loomis (NATURE, Aug. 6, 1927, p. 189) are another example of the important conclusions which may be derived from a study of the interesting phenomenon of ultrasonic stationary waves. Velocities of sound in various, liquids were determined here by the ultrasonic stationary wave method some years ago; some of these results have already been published (Trans. Roy. Soc. Can.,3, 141; 1923; 159, 191, 197; 1925; 79; 1927); others were reported to the Canadian Research Council (Report, Boyle and Morgan, 1924). The ‘detector’ of the standing waves in these experiments was ‘nodal dust figures,’ something like the figures in a Kundt's tube, but less precision was claimed for the results than is claimed by the authors above.Pierce also carried out very precise experiments on the velocity of sound in gases (Proc, Amer. Acad., 60, 6, 271; 1925) by tho ultrasonic method, the detector of the standing waves in his experiments being a milli- or micro-ammeter in the associated grid-circuit of tho electric generating tube. In fact, Hubbard and Loomis's experiment does for liquids what Pierce's did for gases, with tho exception that thoir standing wave indicator is a neon tube instead of a milli-ammeter. Tho purpose of this note is to point out that the presence of thoso ultrasonic stationary waves in a liquid can easily be demonstrated a,nd visualised by making use of another phenomenon, namely, that of ultrasonic cavitatioii, or the production of bubbles in the liquid by the waves themselves. In our work in this laboratory nodal layers of bubbles, a half wavelength apart, have been produced in a tank of liquid between an ultrasonic generator and a reflector; and some months ago Messrs. Taylor and Sproule arranged an apparatus for ultrasonic waves in which a bell-jar was sealed to the face of an ultrasonic generator Liquid was poured in the bell-jar and the pressure in the air-space above it could be reduced by a connectec pump. On working the generator, stationary waves were produced in the vertical column of liquid above it, the air-liquid surface serving as reflector. The pressure in the bell jar and the voltage applied to the generator could be adjusted to result in the production of either large or small bubbles in the liquid When large bubbles were produced they rose rapidly through the liquid, but the small bubbles, especially at very high frequencies, could be made to stay suspended in the liquid in layers parallel to the reflecting surface. The layers were half a wave-length apart, and measurements of wave-lengths and velocities could readily be effected. Our purpose, however, was not to measure wave-lengths but to study cavita-tion, on which subject papers are in course of publication.The experiment is a very striking one, and in our work the nodal layers of bubbles were particularly regular and distinct at frequencies around 170,000 cycles per second. In addition, and as pointed out by Hubbard and Loomis, the column of liquid can be thrown into resonance, the condition of exact resonance in our experiment being indicated by a slight humping of the liquid at the free surface. The height of the hump depends on the intensity of the radiation, and if the liquid be slowly drained from the bell-jar the humping recurs every time the free surface passes through the nodal levels. In this way incidental measurements were taken of half-wave lengths and velocities. In all the determinations of velocity of sound by the ultrasonic method made in this laboratory in the last few years, we have found no detectable change of velocity with frequency, in solids or in liquids, within a range of frequency extending from 30,000 to 600,000 cycles per

ISSN:0028-0836    

DOI:10.1038/120476b0

出版商:Nature Publishing Group    

年代:1927

数据来源: Nature