MODERN CHEMISTRY AND ITS WONDERS Photo, E.N.A. A FUTURE CENTRE OF CHEMICAL INDUSTRY. Kaieteur Falls. The most wonderful in the world. With a height of 741 feet and a breadth of over 350 feet and set in majestic scenery in the Potaro River in British Guiana, this fall could supply 2| million horse-power, and will, no doubt, in the near future be a great industrial centre. MODERN CHEMISTRY AND ITS WONDERS A POPULAR ACCOUNT OF SOME OF THE MORE REMARKABLE RECENT ADVANCES IN CHEMICAL SCIENCE FOR GENERAL READERS BY GEOFFREY MARTIN, D.Sc., PH.D. FIRST-CLASS HONOURSMAN IN CHEMISTRY OF LONDON UNIVERSITY AUTHOR OF "TRIUMPHS AND WONDERS OF MODERN CHEMISTRY," "PRACTICAL CHEMISTRY," "INDUSTRIAL CHEMISTRY," "THE HALOGENS," "CHEMICAL LECTURE DIAGRAMS," "RESEARCHES ON THE AFFINITIES OF THE ELEMENTS," ETC. ETC. Yet I doubt not through the ages one increasing purpose runs, And the thoughts of men are widened with the process of the suns. TBNNYSON ILLUSTRATED NEW YORK D. VAN NOSTRAND COMPANY TWENTY-FIVE PARK PLACE 1915 PRINTED IN GREAT BRITAIN MO' :? - *J '' PREFACE MY recently published book Triumphs and Wonders of Modern Chemistry met with such an enthusiastic welcome by the chemical reading public, having run through two editions and been translated into Russian in the compara- tively short time which has elapsed since publication, that when my publishers approached me with the request to write a companion volume to that work, treating of matters omitted for want of space in the first book, I gladly acceded to their proposal. The present book is the result. The treatment is popular, technicalities being avoided as much as possible. However, in it I suppose the reader to be familiar with the ordinary conceptions of chemistry, such as have already been explained in a popular manner in the first book. The book is not in- tended for students wishing to study for one or other of the innumerable examinations of our somewhat chaotic educational system. Rather it is intended to interest the cultured general reader in some of the really wonderful achievements of scientific chemistry. The subjects chosen include both technical and pure scientific advances, with which the writer has had special opportunities of be- coming conversant. The reception accorded to the first volume, not only in the reviews but also fn the numerous letters which have reached me from practically all parts of the world, has convinced the writer that the work met a real want and that a considerable demand exists for a book of this type. There exists a wide public interested in scientific problems, 3573Si vi MODERN CHEMISTRY AND ITS WONDERS who have neither the leisure nor the inclination to master the technicalities and enter into the minutiae of the regular text-book of chemistry the latter type of book also labours under the disadvantage that only such things can be discussed therein as are likely to have academic ex- amination questions set on them. In addition to interesting general readers, the book may possibly prove useful to popular lecturers and chem- istry teachers in need of interesting illustrative facts for their routine chemical classes. Popular books on science, although depreciated by professional scientists, yet serve an extremely useful pur- pose in bringing home to the mass of the people the enormous importance of Science to the State. The greatest care has been taken to keep the subject matter thoroughly up-to-date. Much of the material here appears in book form for the first time. In every case the most recent authorities, not only English but foreign as well, have been consulted. No one authority has been slavishly followed, but an endeavour has been made to put every fact in a fresh and original way. Consequently the reader will find many old problems presented afresh in a novel form and treated on lines different from those usually adopted in the ordinary chemical text-book. By such means I hope to bring the reader into immediate contact with the thoughts of the great leaders of science, whose ideas, usually buried away in the transactions of learned societies, are inac- cessible to all but the specialist. Seeing that this book is being issued during our struggle with the Germans, it will not be irrelevant to mention that for many years chemists have been urging that in any war that we might have with Germany, our enemies would be all the more formidable because of PREFACE vii their high scientific education and attainments. The scientists of this country have been advocating that there should be national encouragement and support of the useful kind of scientific man, that our manufacturers should employ men who have scientific qualifications, and that into the ranks of those who govern us there should be introduced a much larger leaven of men of science. Unhappily this advice fell upon deaf ears. A war with Germany is, in a great measure, a contest be- tween chemists, and British chemists believe that if the government would have listened to them, the Germans would have been beaten in the early stages of the great war, and that thousands upon thousands of lives would have been saved ; they say that in the Autumn of the year 1914, Germany was saved from a crushing defeat because she had possessed the sense to encourage her chemists. In these pages, the Author hopes that he will be able to reveal the marvels of chemistry, and at the same time to make plain the importance of scientific studies in national affairs. My best thanks are due to Mr. W. P. Dreaper, Editor of the Chemical World, who allowed me to reproduce my article on " Metallic Firestones/'which first appeared in that journal under the title " The Pyrophoric Alloy Industry," and also gave me permission to reproduce a picture of the cultivation of Sugar Beet. To Dr. Lander, Professor of Chemistry at the Royal Veterinary College, London, I am indebted for several curious and interesting facts which do not seem to be generally known. To Dr. Henry Sand, of Nottingham University College, I am indebted for illustrations of the apparatus used in Electro-chemical Analysis a subject which has been much advanced by his researches. To Sir Henry Roscoe, F.R.S., I am indebted for leave viii MODERN CHEMISTRY AND ITS WONDERS to quote from his interesting Life and Experiences. To Mr. G. W. Clough, B.Sc., I am indebted for several valuable suggestions. To the late Professor R. K. Duncan and to his publishers, the A. S. Barnes Co. of New York and Messrs. Hodder & Stoughton of London, I must express my best thanks for leave to quote from The New Knowledge. Messrs. Crookes & Reynolds' Diagram of Atomic Weights is reproduced by kind permission of the British Association. The picture of the Pennycraig Explosion is reproduced by kind permission of the South Wales Institute of Engineers from Professor Gallaway's Colliery Explosions. The illustration of the " Will-o'-the-Wisp " is re- produced by permission of Messrs. W. & R. Chambers, Ltd., from The Gallery of Nature. The two illustrations of Asphalt Digging in Trinidad are reproduced by permission ot the Institution of Mining Engineers. The illustrations of a Malt House and Mash Tuns are reproduced by per- mission of Messrs. A. Guiness & Co., Ltd. The curve of Atomic Volumes is reproduced by permission of Messrs. Blackie & Son, Ltd., from Caven and Lander's Systematic Chemistry. The Chemical Society of London gave per- mission to reproduce the illustrations of Dr. Sand's apparatus for Electro-chemical Analysis. Professor Joly of Dublin and his publishers, Messrs. Constable & Co., Ltd., kindly gave me permission both to quote from and to use some illustrations of the book Radio- Activity and Geology. The Editor of Cassiers Magazine gave me leave not only to quote some extracts from the journal, but also to use some of the illustrations. To Messrs. Fred. Bayer & Co. I am indebted for the photograph of the picture entitled Where German Work-People live." The photograph of Mendeleff was supplied by the photographer, Warwick Brooks of Manchester. The illus- trations of apparatus used in cutting and welding by the PREFACE ix oxy-acetylene flame were supplied by Messrs. Carbic, Ltd. Messrs. Baer & Co. supplied the blocks for illustrating the article on metallic fire-lighters. Messrs. Charles GrifBn & Co. kindly gave me per- mission to quote certain passages from Dr. Wynter Blyth's book on Poisons. Messrs. Macmillan & Co. courteously gave me per- mission to quote from Kingsley's Scientific Essays. To all of these I wish to return my best thanks for the assistance rendered. GEOFFREY MARTIN. UNIVERSITY OF LONDON. CONTENTS CHAP. PAGB I. THE WONDERLAND OF MODERN CHEMISTRY . . i II. THE ROMANCE OF SOME SIMPLE NITROGEN COM- POUNDS 24 III. THE ROMANCE OF EXPLOSIVES 51 IV. RADIUM AND THE NEW CHEMISTRY .... 88 V. THE MYSTERY OF THE PERIODIC LAW . . .112 VI. THE RADIO-ELEMENTS AND THE PERIODIC LAW . 135 VII. MODERN ALCHEMY 150 VIII. APPLICATIONS OF ELECTRICITY TO CHEMISTRY . -157 IX. THE ROMANCE OF THE HYDROCARBONS . . . 175 X. THE ROMANCE OF SUGAR 225 XI. THE ROMANCE OF ALCOHOL . . - . . 242 XII. THE ROMANCE OF COAL-TAR . . . 262 XIII. THE ROMANCE OF COMMON SALT .... 291 XIV. METALLIC FIRESTONES 328 XV. ARTIFICIAL PRECIOUS STONES 336 INDEX ........ . 349 LIST OF ILLUSTRATIONS PLATES KAITEUR FALLS ...... Frontispiece PLATE FACING PAGE 1. MANUFACTURE OF NITRO-GLYCERINE ... 60 2. INTERIOR OF THE WASHING HOUSE OF A NITRO- GLYCERINE PLANT ...... 60 3. SHAPING CHARGES OF GUN-COTTON WITH A BAND SAW 72 4. CHISELLING AND TURNING BLOCKS OF GUN-COTTON FOR CHARGING SHELLS 72 5. THE BATTLESHIP LIBERTE AFTER THE EXPLOSION OF B-POWDER -76 6. PORTRAIT OF MENDELEEFF . . . . .114 7. REYNOLDS-CROOKES DIAGRAM OF ATOMIC WEIGHTS . 130 8. THE VICTORIA FALLS . . . . . .162 9. NIAGARA FALLS 162 10. WATER-POWER HARNESSED TO PRODUCE ELECTRICITY 166 11. ELECTRIC FURNACES, NIAGARA FALLS . . .166 12. DR. SAND'S APPARATUS FOR RAPID ANALYSIS^ BY MEANS OF ELECTRIC CURRENT . . . .170 13. AN ANCIENT FIRE- WORSHIPPER'S TEMPLE NEAR BALAKHANI 176 xiri xiv MODERN CHEMISTRY AND ITS WONDERS PLATE FACING PAGE 14. A GLIMPSE OF THE FAMOUS RUSSIAN OIL CITY OF BAKU 176 15. RUSSIAN OIL WELLS AT BALAKHANI . . . .180 1 6. OIL WELLS AT Los ANGELES, CALIFORNIA . . 180 17. RUSSIAN OIL WELL ON FIRE . . . . . 190 1 8. GREAT PITCH LAKE AT TRINIDAD . . .194 19. VILLAGE OF LA BREA, TRINIDAD . . .194 20. THE WILL-O'-THE WISP- . . . . t .198 21. A FIFTY-THOUSAND BARREL STORAGE TANK FOR PETROLEUM IN COURSE OF CONSTRUCTION . . 206 22. DEAD MINERS, OVERCOME BY CARBON MONOXIDE . 206 23. OXY- ACETYLENE BLOW-PIPE FOR PIERCING HOLES IN METAL RAILS ..222 24. CUTTING 9-lNCH THICK ARMOUR BY MEANS OF AN OXY- ACETYLENE BLOW-PIPE FLAME . . .224 25. THE HOME OF THE SUGAR-CANE A SCENE IN JAMAICA , , . 226 26. CULTIVATION OF BEETS FOR THE MANUFACTURE OF BEET-SUGAR 236 27. GROUP OF WORKERS ON A SUGAR PLANTATION, GUADELOUPE . . . . / . . 236 28. BOILING SUGAR FOR MAKING SWEETS AT MESSRS. FRY & SONS' WORKS, BRISTOL . . . .238 29. MALTING FLOOR OF MESSRS. GUINESS & Co.'s BREWERY IN DUBLIN 250 30. MASH TUNS OF MESSRS. GUINESS & Co.'s BREWERY IN DUBLIN 250 LIST OF ILLUSTRATIONS xv PLATE FACING PAGE 31. WHERE GERMAN WORK-PEOPLE LIVE . . .270 32. STRUCTURES OF CRYSTALLISED SALT . . . .296 33. CRYSTAL -CAVE, WIELICZKA SALT MINE ... . 296 34. BALL-ROOM HEWN OUT OF SALT . . . .296 35. ST. ANTHONY'S CHAPEL, HEWN OUT OF SALT . .298 36. A CHAMBER EXCAVATED IN SALT . . . .298 DRAWINGS IN THE TEXT PAGE 1. RAILWAY TRUCKS SET ON FIRE BY NITRIC ACID . 26 2. NITRIC ACID FROM THE ATMOSPHERE . . .3 3. SOLUBILITY OF AMMONIA IN WATER . . . . 35 4. PREPARING AMMONIA BY HEATING LIME AND AM- MONIUM CHLORIDE . . . . .36 5. AMMONIA AND NITRIC ACID . . . . .41 6. DENTIST ADMINISTERING NITROGEN MONOXIDE TO A PATIENT 43 7. THE RADIOACTIVE ELEMENTS . . . . .99 8. CURVE OF ATOMIC VOLUMES 125 9. SODDY'S HELICAL REPRESENTATION OF PERIODIC LAW 133 10. RADIO-ELEMENTS AND PERIODIC LAW . . .141 11. MOISSAN'S ELECTRIC FURNACE 158 12. SECTION THROUGH DR. SAND'S APPARATUS FOR RAPID ELECTRO- ANALYSIS . . . . . .170 13. DR. SAND'S ELECTRODES FOR ELECTRO-ANALYSIS . 172 14. EXPLOSION OF GAS IN A WELL AT SURAKHANI . . 177 xvi MODERN CHEMISTRY AND ITS WONDERS FIG. PAGB 15. OIL BURST AT DROOJBA .183 1 6. EXPLOSION IN A COAL MINE . . . . .203 17. DEATH FROM CARBON MONOXIDE POISONING . .208 1 8. THE SNAEFELL DISASTER BRINGING UP MINERS OVERCOME BY CARBON MONOXIDE . . .215 19. PRINCIPLE OF A SAFETY LAMP A FLAME WILL NOT PASS THROUGH WlRE GAUZE . . . . 2iy 20. DAVY'S SAFETY LAMP . . . . . .219 21. DEATH OF MANSFIELD . . . . .265 22. SODIUM BURNING ON WATER ..... 309 23. MAKING CHLORINE GAS IN THE LABORATORY . -311 24. SUNLIGHT DECOMPOSING CHLORINE WATER, OXYGEN GAS BEING LIBERATED 317 25. EXPLOSION OF HYDROGEN AND CHLORINE GAS BY RAY OF SUNLIGHT ENTERING THROUGH A HOLE IN A SHUTTER 321 26. SIMPLE GAS-LIGHTER 333 27. SECTION OF GAS-LIGHTER . . . . 333 28. CIGARETTE LIGHTER . . . . . .334 29. APPARATUS FOR MAKING ARTIFICIAL RUBIES . . 343 MODERN CHEMISTRY AND ITS WONDERS CHAPTER I THE WONDERLAND OF MODERN CHEMISTRY " And Nature, that old nurse, took The child upon her knee, Saying ' Here is a story book Thy father has written for thee.' 'Come wander with me,' she said, * In the regions yet untrod, And read what is still to read unread, In the manuscripts of God.' And he wandered away and away, With Nature, the dear old nurse, Who sang to him night and day The rhymes of the Universe." So sang the immortal Wordsworth of the wonders of nature. In the following pages I hope to take the reader with me into part of the Wonderland of Modern Chemistry, and to tell him of facts as strange or even stranger than any ever fabled in a fairy tale with the advantage of being perfectly true. But first of all I must say a few words about what we mean by the science of chemistry. The reader, with faint memories of his schooldays float- ing in his mind, may have some sort of idea that chemistry deals with nasty smells, explosions, and such like things. This, however, is a very distorted view to take. 2 MODERN CHEMISTRY AND ITS WONDERS More accurately we may say that chemistry is the science which deals with the different kinds of matter and their various transformations into other kinds of matter. Consequently wood, tea, metals, glass, acids, poisons, perfumes, rocks, air, gases, water in a word, every substance that you can think of, forms a proper object of study of the science of chemistry. The whole great universe about us, from its uttermost heights to its deepest depths, is built up of matter of some kind or other ; and so chemistry must deal intimately with its structure. Our bodies, plants, flowers, and the innumer- able products of modern civilisation be it a railway train or a piece of wall-paper, a palace of marble or a reel of cotton are all built up of matter, and therefore chemistry as a science must underlie all these things. Ultimately all other sciences rest upon chemistry as a basis, for all such sciences finally deal with matter in some form or other. This is what makes chemistry so interesting as a study ; it is continually giving us glimpses of unexpected wonders. Many of the grandest problems of the astronomer who deals with rushing worlds and blazing suns, of the physiologist who treats of living matter and the mysterious vital processes ceaselessly proceeding in every living organism and producing the most astonishing products and effects, of the physicist who deals with the mysteries of light and heat and electricity and the forces which drive matter into motion, are simply chemical ques- tions ; and all these classes of men have at some stage or other to fall back upon the chemist for the elucida- tion of their deepest problems. Even geology is essen- tially a chemical science ; for the wearing down of rocks and the countless changes undergone on the surface of the earth by the action of wind and water, fire and acids, are essentially chemical changes ; indeed, the WONDERLAND OF MODERN CHEMISTRY 3 whole world is but a vast system in ceaseless and rapid chemical change. Since chemistry is the science which deals with the various kinds of matter, and since all industries use as their raw material matter in some form or other, it is obvious that chemistry must be more closely interwoven with the industries of a country than almost any other science. Indeed, for this reason it has been stated that national pre-eminence in chemical industry ultimately means a national world supremacy. Chemistry gives us command of matter, and therefore the empire of the world. The country that produces the best chemists must, in the long run, be the most powerful and wealthy. And why ? Because it will have the fewest wastes and unutilised forms of matter, the most powerful explosives, the hardest steels, the best guns, the mightiest engines, and the most resistant armour. It will have at lowest cost the best manufactured articles ; its food will be the most nourishing and the cheapest. Its inhabitants will be the most healthy and the best developed, the most free from disease and vice. They will be thrifty, resourceful, intelligent, utilising their country's resources in the best possible manner and opposing the least resistance to favourable evolution. Their country will be the least dependent upon other lands, the most prosperous in peace, the most terrible in war. Truly the education of the nation in advanced chemistry and higher physical science is the most paying investment that any country can make. Indeed, one writer goes so far as to suggest that competition between civi- lised nations is merely a competition in the science and applications of chemistry. Therefore it is greatly to be regretted that in England our higher education and 4 MODERN CHEMISTRY AND ITS WONDERS universities are starved the teachers in great universities often living on pittances such as skilled artisans would refuse/ while, still worse, chemical research is greatly 1 Let me give some instances of what is now (1915) nothing less than a national scandal. You can purchase the full-time services of a doctor of Science, one who has discovered several new facts and who has possibly written a couple of books, and who has, in a word, brains, ability and ideas in abundance, for I am ashamed to say it about 130 a year ! This is less than the wages paid to an average clerk of the same age in a bank, far less than that paid to an average civil servant, and even less than that paid to a good fitter in an engineering workshop. The financial position of the scientific worker engaged in research on the fundamental questions of science is pitiable in the extreme. The reader will naturally suppose that, at least, the "teacher- scientists " on the staffs of the great modern universities like those of London, Birmingham, Manchester, Bristol, Liverpool, and Wales, that is to say the men who are the pick of those who pass through the universities, who do the bulk of the very advanced teaching work of these universities much of it laborious evening work all men with brilliant degrees (possessing in nearly all cases the highest scientific degrees attainable, often possessing the doctorate of both an English and a German university), all engaged in researches and making discoveries in science which aid the public in health and sickness, and whose steady but unobtrusive work forms the basis of the great scientific discoveries which from time to time startle the world and lead to the creation of world- wide industries surely such men at least get a fair wage for their work, a wage as good as that, say, of a clerk in a bank or an employee in the Post or Patent Office, or, at least, as good as a second division civil service clerk. Nothing of the sort. They do not even obtain a living wage, still less a pension ! I do not exaggerate. Let me explain. Most of the research work done in England is carried out in our modern universities by the teaching staff". Students do little because (as explained below) our university regulations are ingeniously framed so as to make it unprofitable for them to do it. Now the staff of a modern university is very sharply divided into two classes, viz. pro- fessors and non-professors. All the latter, some of them men of forty, and more, are known as the " junior staff." A professorship represents the greatest pros- perity to which a scientist can reasonably hope to reach. The salary may be put as 600 to 800 a year. Comfortable, you will say. Yes, but meagre com- pared with that of a successful lawyer, surgeon, physician, stockbroker, or man of business. But what of the junior staff? They start at, say, twenty-two to twenty-five years at anything between 100 and 120 a year. Very, very rarely do they ever get more than 200 or 250 a year at forty years of age. The bulk can never obtain professorships, and the few that do ultimately attain to this highest honour seldom do so before they are forty. These men are sweated at a salary which commences at say 120 and possibly goes up to 200 by the time they are thirty-five or forty. They work often from WONDERLAND OF MODERN CHEMISTRY 5 discouraged by the regulations of the chief British universities, who have made it most unprofitable for an average student to indulge in research of any kind. Very different is the German system, where the universities turn out, not mere teachers of little boys or nine in the morning to ten at night at teaching and researching. After middle age (if they survive !) they may with luck expect some improvement. This, then, is what the brilliant university graduate (and only brilliant men are taken on) may expect if he takes up pure science as a profession : Five or six years' hard work for a brilliant degree, fifteen years' apprenticeship of still more laborious and difficult work at an average salary of 175, and then, with luck, but very doubtful, a possible 600 to 800 a year. This is the country's offer to its best scientific brains. Three months' holiday in the year, I hear my readers whisper. Nothing of the sort. The young scientist in these modern universities has to spend the bulk of his holidays in the stifling air of the laboratory working 12, 13, and 14 hours a day at his subjects if ever he is to attain that professorship which looms vaguely in the remote distance. " Poverty " is the excuse put forward by the modern university for sweating 95 per cent, of their teaching staff at this sort of salary. Yet with incredible meanness they forbid them to augment their salary by outside work, and every- one knows that they raise and spend hundreds of thousands of pounds for pre- tentious buildings (what has Birmingham and Bristol spent within recent years on huge buildings ?), in spite of the fact that the average chemical or physical laboratory is as out of date in tiventy years' time as is a modern battleship, and that all that is wanted to carry on the -work are a few corrugated-iron sheds fitted with "working benches with high-pressure water^ gas, and electricity laid on. It is men not buildings that are the need. Even when money is obtained ear-marked for salaries, a few more assistants are appointed at the same meagre wage, the clerks engaged in purely routine work in the office get a " rise," but no improvement in the position of the junior scientific staff ever takes place. The main problem agitating the university authorities seems to be how to secure in- credibly highly qualified scientists at incredibly low salaries. Civil servants are all assured of a living wage by the time they are middle-aged men (say thirty- five or forty) and of a pension afterwards. University teachers, who should rank at least as high as junior second-class civil servants, however, do not attain even this nor do they get pensions. They are told that they must keep " moving on " and that their positions are not permanent. The theory is that they must leave their positions and attain better ones, and the responsibility of the university then ceases though where they are to "move on" to is left delightfully uncer- tain. Postmen, clerks in banks, &c., have not this nightmare hanging over them after years of hard and honourable work. Equally miserable is the pay of technical chemists. Very often they are not paid more than labourers, packers, &c. in spite of the fact that a long and ex- pensive training is necessary to attain full chemical qualifications. 6 MODERN CHEMISTRY AND ITS WONDERS men crammed with bookwork as our universities do but practical men, men trained in methods of research. For the German university regulations made it profitable for the student to take up research work, and later these students were absorbed into chemical industry. And the result ? Germany turned out chemical products of the annual value of 750,000,000 ; and in certain chemical products she dominated the world's markets. Meanwhile our universities are merely multiplying ex- aminations and academic distinctions of all kinds, increas- ing their difficulty and putting all sorts of obstacles in the way of research for students. And yet so long ago as 1877 Huxley remarked: " I would make accessible the highest and most complete training the country could afford. Whatever that might cost, depend upon it the investment would be a good one. I weigh my words, when I say that if the nation could purchase a potential Watt, or Davy, or Faraday, at the cost of a hundred thousand pounds down, he would be dirt cheap at the money. It is a mere commonplace and everyday piece of knowledge, that what these three men did has produced untold millions of wealth, in the narrowest economical sense of the word." Our universities, therefore, should aim at producing not men who know a lot the assimilators of other people's ideas but research men, men of a creative type of thought, who are capable of inventing and producing new things, and are able to harness the forces of nature to their ends. If our university senates see a ghost of a chance they promptly invent some fresh examination for the benefit of the hapless students. 1 They should diminish 1 In almost any modern English university, for example, before a student can attain its highest Degree in Science or Arts he has to pass no less than four or five separate examinations, each of an increasing stage of difficulty, He is, therefore, WONDERLAND OF MODERN CHEMISTRY 7 the number of examinations and increase facilities for re- search as every scientific academic teacher who has had experience in teaching young men and women knows. Make it profitable for your student to undertake research and he will do it with enthusiasm, and boldly plunge into the unknown. Face him with a succession of Chinese- like examinations as our universities now do requir- ing years of study to surmount, and leaving the student jaded and tired to death of mere bookwork at the end of it all, and you find that the average student will never have the energy or freshness left after all those wasted years to face research, which is itself hard and weary work. In England and Scotland our university research laboratories are empty, but our " knowledge-cramming " classes full. In Germany the research laboratories were full and the " cramming " classes empty the result of wise university legislation in the latter country. What has already been achieved by chemical research may be realised when I tell the reader that within the last few years there have been obtained synthetic dyes far brighter and more durable than any natural dyes, artificial fibres far more lustrous than any natural fibres, manufactured scents a thousand times more powerful than any natural scents, wonderful new artificial drugs which have revolutionised dentistry and medicine, abolished pain and disease, and which allow the most astonishing surgical operations to be performed without pain or danger. I might also mention artificial substitutes for bone and ivory, horn and leather, rubber and resins during the whole of his four or five years of student life kept in a turmoil of examina- tions, and the only knowledge which appeals to him is that which will help him to answer a probable examination question. The effect of this mental attitude on the teacher may be easily imagined. He dares not touch on anything except those portions of science which adapt themselves to examination requirements otherwise he loses the interest of his hearers ! 8 MODERN CHEMISTRY AND ITS WONDERS (often superior to the natural articles as regards some properties), and tough transparent substances like celluloid and other film-making materials, which have allowed the wonderful development of living pictures and motion photography. Perhaps, however, the greatest achieve- ment of modern chemists is the discovery of explosives of terrific power, which have enabled man to blast his way through mountain and valley, and have rendered possible those truly astonishing modern engineering feats which are rapidly transforming the whole surface of our planet. When I tell the reader that all these things are but the prelude to far greater achievements, which will ultimately lead to the harnessing of the natural forces of the Universe by man, he will realise that chemical research is no dry and uninteresting subject, but is one which teems with problems, the solution of which will bring into the grasp of the solver prizes of immense value. At one time and that quite recently too terrible epidemics swept across the world, decimating the human race. The great plague, for example, coming from China swept right across Russia and Europe into England. We are told that grass grew in the streets of London and the dead were so numerous that there were scarcely enough men left to bury them ! This was simply an invasion of foreign bacteria, far more deadly than any invasion of human foes ; even at the present time such invasions, causing bacterial diseases, levy a frightful toll upon the human race, killing annually millions of men, women, and children. By the manufacture of bacterial killing substances the so-called " antiseptics " the chemist has done much to save us from disease ; it is safe to state that now it would be impossible for WONDERLAND OF MODERN CHEMISTRY 9 plague to sweep over the world and decimate the whole human race, as it formerly did, not once, but many times. Antiseptics have obviated for ever such a possibility, and the world has to thank chemists for this great advance. At the present time chemical remedies are known for many diseases, and many authorities believe that a time will come when diseases like typhoid and scarlet fever will be as rare as are now fatal mechanical accidents among civilised races. Indeed, many diseases, at one time regarded as very dangerous, are now considered scarcely worse than an ordinary cold. The chemist also protects usfrom professional poisoners, who once flourished in Europe to an almost incredible extent, and who still flourish to some extent in many Eastern countries. In past times almost every man of note went in danger of secret poisoners, and medical science was then not sufficiently advanced to decide whether a man died suddenly in a fit or from a swift poison. Now, however, all this is changed, for by the swift and sure means of chemical analysis the chemist can detect poisons in the human body even after the un- fortunate victim has been dead for months, and so can bring the guilty ones to justice. Secret poisoning, thanks to chemists, is now almost as deadly to the poisoner himself as to the victim ! Chemistry has revolutionised not only the Arts of Peace but also the Art of War. Whence, for example, has come the knowledge that has made possible the long, slow evolution of the rude bow and arrow of the savage into the great guns of to-day ? Surely from the laboratory of the chemist. He has given us our fine steels and our high explosives without which modern armament would be impossible. The modern battleship is but a vast float- ing engineering shop, whose death-dealing appliances derive their irresistible power from explosive chemicals. Like- io MODERN CHEMISTRY AND ITS WONDERS wise the airship, the aeroplane, the waterplane where were they invented ? Not on the battlefield, but in the shed of the scientific inventor ; not until the chemist had discovered how to distil out volatile, explosive components from oil, wherewith to furnish the motive power for their engines, was their advent possible. All these are practical achievements the value of which can be realised by the average man in the street. But chemists have made discoveries which lead us right into a fairy land of science, discoveries which must appeal to the imagination of every thoughtful person, and which enable us to withdraw awhile from the cares of life and enjoy the calm of science : " The silence that is in the starry sky, The sleep that is among the lonely hills." We all know that the astronomer deals with things of infinite vastness, the grandeur of which, the revealing of series of worlds stretching away in endless vistas into space, strike with awe even the most thoughtless mind. The chemist has revealed equally wonderful things in the domain of the infinitely small ; he has directed the arm of reason into regions of almost inconceivable minuteness to weigh and measure the tiny atoms which build up matter objects so small that they lie as far beyond the vision of the most powerful microscopes as these carry their vision beyond that of the naked eye. Nay, recently the chemist has passed beyond the atom itself and has revealed to our astonished gaze a domain in which the atoms themselves loom as great galaxies built up of still tinier particles. And thus the chemist has given us a truly astonishing vision of universe within universe reced- ing into the infinitely small just as the astronomer has revealed to us universe within universe stretching away into the infinitely great. The whole vista thus opened out by WONDERLAND OF MODERN CHEMISTRY n modern chemistry lays bare hitherto unsuspected depths of complexity in the commonest and most insignificant things about us. Tennyson long ago expressed this grand truth in the lines : " For Knowledge is the Swallow on the lake That sees and stirs the surface-shadow there But never yet hath dipt into the abysm, The abysm, of all abysms, beneath, within, The blue of the sky and sea, the green of Earth And in the million-millionth of a grain Which cleft again for evermore, And ever vanishing, never vanishes, To me, my son, more mystic than myself Or even than the nameless is to me." And now what of the men who have achieved these wonders the workers in the rank and file of the great scientific army ? What manner of men are they ? Well it must be confessed that the majority are very ordinary individuals, certainly not even approximately as dis- tinguished looking as poets or artists or actors or soldiers. They wear neither long hair nor exaggerated neckties, nor have their clothes an extraordinary cut. Indeed, beyond the fact that they are somewhat more shabby than the ordinary business man there is nothing to dis- tinguish the average scientist from the average man in the street. The popular notion that Science is a happy family of mutually admiring absent-minded philanthropists, each striving for the benefit of the human race, is very far from being a picture of the reality. So far from thinking solely of benefiting the human race, most pro- fessional scientists, I am afraid, are much more concerned about earning enough money to buy their wives nice hats and bring up their families respectably ! In fact, they are just ordinary, everyday men. The scientific world is a very restricted one with prizes few and far be- 12 MODERN CHEMISTRY AND ITS WONDERS tween, where the struggle for survival is as fierce as in any natural species, and where bitterness and spite and disappointed hopes are as prevalent as in the industrial or artistic world. As in other branches of activity, the " top " is no limitless plateau with room for all scientists. Rather it is a spiky pinnacle whereon a few eminent professors uncomfortably sit, and occupy most of their spare time in shoving down their junior colleagues who would presume to climb to the same level. More often than not great scientists pass their lives in obscurity. Yet they have this consolation their achieve- ments will ultimately be recognised and will spur unborn generations on to fresh endeavours : " He is not dead whose glorious mind Lifts thine on high. To live in hearts we leave behind, Is not to die." How often do we, when engaged in investigating new and unknown regions of science, come across the work of men dead and forgotten scores of years ago ; their personality again lives before us in their writings, and we idly wonder concerning their forgotten struggles and difficulties. There is one thing every scientific investigator must bear in mind and that is accuracy. Facts which are inaccurate and which live in the literature of science for a time, ultimately come home to roost a Nemesis to the hasty and inaccurate worker. As Goethe put it : " Haste not, let no thoughtless deed Mar for aye the spirit's speed. Ponder well, and know the right, Onward then, and know thy might ; Haste not, years can ne'er atone For one reckless action done." As a class, successful scientists have one or two small WONDERLAND OF MODERN CHEMISTRY 13 characteristics which differentiate them somewhat from other classes of men. In the first place, a scientific discoverer owes his success to a highly developed but peculiar mental characteristic and that is excessive attention to minute detail. His is a mind which frets itself into a frenzy about minute dis- crepancies which an ordinary individual would regard as too minor for serious attention. Nearly all great discoveries have been made by this attention to little discrepancies. " Powers of careful observation " is the euphemistic term by which scientists denote this necessary character- istic for discovery. Consequently your successful scientist tends to attach exaggerated importance to little things. He is a "crochety," "finicking" individual. This is why scientists are always quarrelling, disputing about petty details. They are remarkably jealous of each other, usually referring to work other than their own as " very ordinary " if it is a careful, exact piece of research ; whereas it becomes " too speculative " if the worker goes in for any degree of originality, and the poor man is always spoken of (behind his back) as " quite unsound." Most eminent scientists in any one branch are deadly enemies. Indeed, it is a most entertaining -if not a dig- nified spectacle, to see one eminent professor " slating " another eminent professor's book in hypercritical reviews. Moreover, those professors who write books look down on those who merely do research work, and vice versa. Their ideas are usually distorted as regards the relative value of things, and it is this which has led to the current English notion that a scientist is " unpractical " and a " Fuss pot." I doubt whether scientists could govern a state any more than artists or actors could. Scientists deal with Nature, but Statesmen deal with men, and the qualities which tend for success in the one branch of 14 MODERN CHEMISTRY AND ITS WONDERS activity will often be the antithesis of the qualities needed for success in the other sphere of activity. The average English business man whose success in life depends entirely upon exercising commonsense when brought into contact with the new, strange world in which the scientists wander, views with blank aston- ishment these men disputing, quarrelling, and attacking each other about what seem to him the veriest trifles ; he classifies the whole pack as a lot of semi-maniacs. This attitude of mind is largely responsible for the utter lack of sympathy which prevails in England between scientists and the business world, and is the real reason why scientists as a class are so miserably poor. "The beakers and flasks of the scientific investigator," said the great German chemist, Emil Fischer, " are minute compared with the vats employed by the chemical manu- facturer. This relative difference in size also corresponds to the comparative wealth of these two classes of men." Certainly if scientists as a class had any business ability they would have long ago improved the pittances which are now paid to fully trained men. Scientists simply do not realise their power, and fail entirely to act in a united manner to secure proper recognition of their services. They should be protected from exploitation, especially as the average Englishman thinks that it is the duty of every scientist to be a " martyr to science." These peculiarities of scientists have been noted for centuries. Thus in the old work entitled Physica Sub- tenanaea, published nearly two hundred years ago, we read the following : " The chymists are a strange class of mortals impelled by an almost insane impulse to seek their pleasures among smoke and vapour, soot and flame, poisons and poverty, yet among all these evils I seem to live so sweetly, that WONDERLAND OF MODERN CHEMISTRY 15 may I die if I would change places with the Persian King." Charles Kingsley, who undoubtedly would have made a great scientist if his walk in life had lain in another sphere, speaks some admirable words on the disinterested labours of scientists. They are well worth quoting, although I am afraid they envelop the scientist with an idealistic atmosphere which one better acquainted with this species of the human race would know is far removed from the reality. In a lecture l delivered to the Royal Institution many years ago, he said, speaking of Science : " Her votaries have not as yet cared much for purple and fine linen, and sumptuous fare. There are very few among them who, joining brilliant talents to solid learning, have risen to deserved popularity, to titles and to wealth. But even their labours, it seems to me, are never rewarded in any proportion to the time and the intellect spent on them, nor to the benefits which they bring to mankind ; while the great majority, unpaid and unknown, toil on and have to find science her own reward. . . . They are engaged in a war a veritable war against the rulers of darkness, against ignorance and its twin children, fear and cruelty. " I can conceive few human states more enviable than that of the man to whom, panting in the foul labora- tory, . . . Isis shall for a moment lift her sacred veil, and show him, once and for ever, the thing he dreamed not of ; some law, or even mere hint of a law, connecting them all with each other and with the mightier whole, till order and meaning shoots through some chaos of scattered observations. Is not that a joy, a prize, which wealth cannot give nor poverty take away ? " 1 Kingsley, Scientific Essays, published by Macmillan & Co. 16 MODERN CHEMISTRY AND ITS WONDERS Kingsley elsewhere observes of the scientist : "He is following a mistress who has never yet con- ferred aught but benefits on the human race." And, yet, to this very day, the scientist in the stage play or average novel is always represented as a villain, seek- ing to murder someone by the aid of mysterious powers ! Tennyson, who had possibly an intimate personal knowledge of scientists, had a decidely lower opinion of them than Kingsley. Tennyson naturally thought, that men who dealt with the mysteries of the universe ought to possess lofty and poetic minds. He found them, how- ever, like ordinary mortals, concerned with petty things and petty spites, and so in " Maud " he described them as having : " An eye well-practised in Nature, a spirit bounded and poor." However this may be, I do not think that anyone can deny the really astonishing achievements of modern chemists, or dispute the truth of Kingsley's words : " What physical science may do hereafter I know not ; but as yet she has done this : She has enormously in- creased the wealth of the human race ; and has therefore given employment, food, existence, to millions who, with- out science, would either have starved or have never been born." It is not the fault of science that Germany has harnessed her to the chariot of death and destruction. Science is potent beyond all belief for good but she puts terrible powers into the hands of madmen. Chemists have even dared to leave the inanimate world and have attacked the problem of life itself. In earlier times, even so recently as the first de- cades of the nineteenth century, men looked with awe WONDERLAND OF MODERN CHEMISTRY 17 upon the mysterious region of vital chemistry. They saw plants and animals produce with ease and in abun- dance innumerable curious substances which, in the laboratory, men failed altogether to produce ; to mention a few : beautiful dyes, which tinge plants and animals the most exquisite colours, from the soft pink of the rose, through shades of glorious red of the carnation, to wonderful tints of yellow, green, and purple ; sweet tasting sugars, beautiful perfumes, powerful poisons, and wonderful healing drugs, all produced by the strange chemistry of plant and animal life. Yet up to the year 1827 no man had ever produced in the laboratory a single one of these bodies, and chemists hovered awe- stricken at the entrance of this vast chemical domain, fearing to enter, and regarding all these products of the wonder- ful life-activity of animal and vegetable life as the direct manifestation of mysterious vital forces which prevailed only in living matter and which produced results which no man could imitate. Indeed, not a few persons were of the opinion that even to dare to enter this region, and to endeavour to understand the processes by means of which animals and plants produced these astonishing results, was something in the nature of blasphemy, being in their opinion attempts to spy upon the secrets of the living God and to observe how he brought forth in secret the wonders of the living world. And so it came about that the whole scientific world was in 1827 thrilled by the announcement that a scientist had actually made a substance artificially which until that time had been brought forth solely in the laboratories of the animal body. For in that year the great German chemist Wohler succeeded in making in an artificial manner from purely mineral substances the white crystalline substance called urea a typical vital product. We can well imagine the wonder and delight with which Wohler first B i8 MODERN CHEMISTRY AND ITS WONDERS gazed upon artificial urea a substance now manufactured artificially in tons at a time and solemn must have been the thought which flashed through his mind that now for the first time in all the ages since the world began, he gazed upon an artificial organic product. This feat was the forerunner of many other similar ones. Fats were made artificially so far back as two generations ago by Berthelot of Paris. Artificial grape sugar saw the light twenty years ago at Wiirzburg. Artificial dyes innumerable are now manu- factured in tons at a time, and to-day great industries have arisen in which millions of pounds' worth of substances, formerly only known as the product of vital activity, are annually produced by purely chemical means. It is therefore altogether hard to realise the time when the production of a single artificial organic substance was the cause of endless astonishment. Now such products are so common that men have ceased to take any notice of them. It is true that only comparatively simple organic bodies have been thus obtained in the laboratory. The immensely more com- plex organic substances, such as albumen, have not yet been synthesised ; but yet recently a beginning has been made. Thus within the last dozen years Emil Fischer in Berlin has worked out methods for the artificial building up of albuminous substances, and in 1911 showed a small bottle full of the substance thus obtained. This synthetic protein, however, is anything but cheap. The starting materials for its preparation cost about 50, and the labour involved in its preparation must have been much more costly than even this, and so the substance has not as yet appeared on the breakfast table as a food ! It was exhibited simply as a chemical curiosity. But one must remember that the chemical curiosities of to-day are to-morrow world-wide articles of commerce, WONDERLAND OF MODERN CHEMISTRY 19 and so this synthetic protein may be the forerunner of a world-industry of artificial foodstuffs. The reader must recollect, too, that at the present time the whole human race has to rely for food and warmth upon grains, roots, fruits and fibres, and upon animals to whom organic nutriment is as essential as it is to us. It is true that Science can do much by intensive cultivation and by scientific feeding to increase our planet's stock of foodstuffs. But there is an ultimate limit to the productive powers of the soil of our planet, and although we may increase it greatly by scientific means, yet the population will increase in equal ratio and no doubt will go on increasing long after the reproductive power of the soil has reached its limit. But what a new vista would open out if Science should discover some means of enabling us to feed on inorganic material such as surrounds us on every side in untold billions of tons 1 The atmospheric nitrogen, which is about us on every side and of which some seven tons' weight rests on every square yard of the world's surface sufficient nitrogen for nearly fifty tons of living matter is even now being fixed by electrical means and converted into manures, and so ultimately* into food. But Emil Fischer's synthesis of simple proteins is a stage further than this. It represents the artificial production of actual foodstuffs by purely chemical means, from the purely inorganic materials which surround us on every side in millions of tons. And if Science should so advance as to make the production of this artificial food an easy matter giving us bread, so to speak, from the air and stones about us then food would become so inexpensive and so abundant that the human race could multiply into numbers which altogether baffle conception. The difficulties to be surmounted, however, are stu- pendous. Nevertheless the very bread we eat, and most 20 MODERN CHEMISTRY AND ITS WONDERS of our foodstuffs, may yet be produced on a manu- facturing scale by chemical means. Then, indeed, a new epoch will have dawned for the whole human race. Mankind will have reached a new stage in his upward development. And what the end of it all will be we cannot even guess. It may be that we are just in the beginning of the beginning, as Tennyson hinted in the pregnant words : "Well were it not a pleasant thing To fall asleep with all one's friends And every hundred years to rise And leave the world, and sleep again : To sleep thro' terms of mighty wars, And wake on Science grown to more, On secrets of the brain, the stars, As wild as aught in fairy lore ; Titanic forces taking birth In divers seasons, divers climes, For we are the Ancients of the Earth And in the morning of the times." On the other hand, it may be that Science will not continue to advance at her present swift rate of progress. 1 1 One great danger to the ultimate progress of Science is the rise into power of the great Scientific Societies, whereby the whole of crystallised scientific thought becomes vested in the hands of a few men, who, like the Theological Societies of old, will crush and suppress any attempt of scientists to break away from established tenets or establish free modes of thought among themselves. Paradoxical though it may seem, a period of reaction follows the work of every great original thinker, and the mistakes or influence of a Newton or a Helmholtz often paralyse for many years the labours of workers in whole branches of thought which were traversed by these great minds. A great thinker like Aristotle probably put back scientific thought for 2000 years ! Now when immensely rich and immensely powerful International Scientific Societies (Science is International) adopt as fairly and irrevocably established certain great theories and methods of investigation, their power to crush free thought and free investiga- tion is enormous, and their motives in doing it will be identical with the motives which impelled the Priesthood to crush free-thinkers in the Middle Ages namely the firm conviction that in so doing they are benefiting the human race and doing the right thing. The reader must remember that human nature is un- WONDERLAND OF MODERN CHEMISTRY 21 It may be that a long period of stagnation, lasting for thousands of years, may follow the present epoch of enhanced activity. But of this period of stagnation we can at present detect no sign. Science, aided by thousands of busy brains, is striding onwards so swiftly that no single man can keep pace with her or prophesy into what unknown regions of fact and thought she will next launch us. As yet we are far from any information which will lead us to expect the artificial making of any piece of living matter in our laboratories. The simplest organism is marvellously complex, the end product of billions of years of evolution in Nature's laboratory. However "biological chemistry" as the science which deals with vital processes is called is already well-estab- lished and rapidly advancing. Its progress is fraught with the most momentous consequences to the human race. In biological chemistry most processes are carried on by means of mysterious substances called " enzymes " which up to this time have never been obtained in a pure condition, but which cause chemical changes to take place without themselves undergoing much change. Now since we are dependent, not only for the assimilation of our very food, but also for a large part of ' our luxuries and comforts, upon these changes, it will readily be seen that when man acquires the power of guiding them very strange things may come to pass. Most of changed, and that the irresistible tendency of all men is to resent any attempt to deviate from the established order of things. Science can only advance by allowing freedom of thought, and even when men hold opinions which we feel absolutely certain are incorrect, tolerance should be extended to such views. Advances are always made by minorities, whose opinions, gradually gaining ground, finally become majorities^ only in turn to be assailed by other minorities. The power of the few men who control the English and the German Chemical Societies is, at the present time, simply enormous. They completely sway between them the whole of scientific chemical activity in this country and abroad. Should such men become too conservative they could block and sup- press original ideas and make chemistry a stagnant science. See, for example, p. 119. 22 MODERN CHEMISTRY AND ITS WONDERS the countless chemical changes which occur in the animal and vegetable kingdoms some of them of a truly wonder- ful nature are due to the action of these enzymes. Many of the oldest industries of the world's history the making of wine, beer, and vinegar, the souring and clotting of milk to form cheese, the tanning of hides are dependent upon the formation of enzymes in the bodies of bacteria or in living tissues. The same is true of the fermentation processes employed in the retting of flax, in the curing of tea and tobacco, coffee and cocoa. Even the coagula- tion of blood from a wound (which stops bleeding) and the processes of digestion are all dependent upon enzymes. So also are modern processes for disposing of sewage by bacterial oxidation. Now that these results of biological science are being applied in the service of industrial and economic chemistry, the results which will ultimately follow are altogether difficult to foresee. The influence of these discoveries on our ideas of the mechanism of life itself is very great. Although the fundamental secret of the nature of life still remains, and will long remain, hidden from our eyes, yet it is indisputable that much which was quite recently regarded as vital and inseparable from living matter has been proved to depend upon conditions which can be realised 'apart from the living organism ; it is indisputable that the veil hiding the actual crude material mechanism by means of which the vital processes are carried on, is being rapidly drawn aside by the chemist. But unfortunately this brings us little nearer to the mystery of life itself. For example, what is Thought and all the allied mental phenomena ? How can any rolling con- course of atoms thrill thought and consciousness into matter ? It avails not how complex a system we conceive of flashing atoms and sub-atoms, for our chemistry cannot explain how thought arises from their motions WONDERLAND OF MODERN CHEMISTRY 23 and arrangements. It may be true that the notion of a flower or a picture or even a complex mental resolution all take their rise in definite atomic motions or collisions going on in our brains but these changes do not constitute or explain the arising thought itself. A man is but an aggregate of material atoms whirl- ing, wheeling, colliding in ceaseless change. And Science, before she can pretend to have solved the problem of life, must explain how such a mere aggregate of so many pounds' weight of carbon, nitrogen, phosphorus, oxygen and hydrogen atoms can evolve thought and conscious- ness by the mere relative movement of these atoms. At present Science has no standpoint wherefrom to plunge into such mysteries ; she has no sure anchoring ground from which to venture into the unsounded depths of Mind, to conceive of its generation and flight. She has nothing definite to lay hold of in such shadowy realms, nothing to grip and guide her experimentally as in the more material sciences such as chemistry and physics and mechanics, where experiment reigns supreme. And so, in spite of all the enormous advances of Science within the last few centuries, we are, apparently, as far as ever from the solution of the great mystery of life itself. Even to-day, after a' century of strife, Science still knows not whether Wordsworth was right when he wrote the grand words which represent the intuitive belief of unnumbered millions of the human race : " Our birth is but a sleep and a forgetting ! The Soul that rises with us, our life's Star, Hath had elsewhere its setting And cometh from afar. Not in entire forgetfulness And not in utter nakedness But trailing clouds of glory do we come From God, who is our home." CHAPTER II THE ROMANCE OF SOME SIMPLE NITROGEN COMPOUNDS NITROGEN, like carbon, forms an innumerable multitude of compounds. So numerous are they, indeed, that a large book could be written about them alone. These compounds are among the most important known, com- prising as they do the bodies which build up living matter, explosives, medicines, drugs and dyes in a word all those bodies which serve the thousand and one wants of civilised peoples. Interesting as the subject would be, we cannot treat of these substances here. I wish to direct the reader's attention to some quite simple nitrogen compounds, which are of surpassing interest at the present time. The fate of a world probably rests upon two simple compounds of nitrogen namely, nitric acid, HNO 3 , and ammonia, NH g . This is a fact sufficient to direct attention to these two substances, old friends of our schooldays as they are, and invest them with a fresh interest. Indeed they form the centre of attention of the scientific world at the present time, since it is directly or indirectly from these two bodies that all our effective explosives are made. Deprive a nation of them, and slowly but surely her offensive power declines and ultimately vanishes, for with them goes her means of manufacturing explosives. More- over, her supplies of food must dwindle and fall far below the needs of any congested population, because nitrates 24 SOME SIMPLE NITROGEN COMPOUNDS 25 and ammonium salts are needed by the land for manurial purposes, to supply nitrogen to make crops grow. Let us, therefore, first of all concentrate our attention on these two- substances. Of the two nitric acid, HNO 3 , has possibly the greater commercial importance, and so we will take that first. It is a colourless liquid. The pure acid is terribly corrosive, attacking organic material such as paper, wood, and skin extremely rapidly. Most metals dissolve in it, evolving poisonous nitrous fumes. Moreover, the strong acid is decomposed by light, evolving oxygen gas. Hence if an air-tight bottle of the pure acid is placed in a brightly lighted room, enough oxygen may be gradually formed to cause such a pressure inside that the bottle explodes and hurls the fluid in all directions on to the wooden floors and benches. When this occurs invariably the wood takes fire and burns furiously. Some chemical laboratories have been burnt down in this way. The acid is, therefore, always preserved in dark blue bottles in a dark place. For a similar reason it is very difficult to send pure nitric acid in large quantities long distances by rail. For if the glass vessel in which it is confined should happen to break, then the strong acid pouring over the waggon almost always sets it alight. Conse- quently the substance, when in large quantities, is sent diluted with water. In the colour industry, however, it is absolutely necessary to have a very strong acid free from every trace of water. The, difficulty of transporta- tion was ultimately got over by mixing the strong acid with an equal volume of strong sulphuric acid. The mixture can be sent in iron vessels, and consequently without danger, since the iron becomes " passive " or in- soluble in acid, owing to, some authorities say, a thin coating of iron peroxide forming a protecting film over it. Owing to the terribly corrosive properties of nitric 26 MODERN CHEMISTRY AND ITS WONDERS acid many fearful accidents have happened, and of these the most dramatic was that which occurred some years ago in a large German dye-factory. A workman over- balanced himself and fell into a large vat containing a boiling mixture of strong nitric and sulphuric acids, such as is used for dissolving dyes. There was no one in the FIG. 1. Railway trucks set on fire by nitric acid. building to hear his last despairing cry, and when, later, the man was missed, nowhere could a trace be found of him. His vanishing was an absolute mystery which no one could account for. Some people thought that the man had secretly fled the country and gone to America, others that he had met with an accident. The manager of the works suggested that he had fallen into SOME SIMPLE NITROGEN COMPOUNDS 27 the acid and had been dissolved, hair, flesh, boots, clothes, bones and all. The weeping wife now laid claim to his insurance money, but the assurance officials refused to pay out anything. " Produce us evidence of death," they said, " and we will give you the money. How do we know that your husband has not simply secretly left the country ? " So the poor widow was in a sad plight and at her wits' end what to do. She appealed to the manager of the works, and he resolved to solve the problem. Being a chemist, he knew that the human body contains quite a considerable amount of phosphorus, which must be found in the acid (if the man had really fallen into it) in the form of phosphoric acid. So he caused an analysis of .the liquid to be made, and sure enough found a large amount of phosphorus present, such as repre- sented the amount known to be in the body of a full grown man. This evidence was then presented, and the end of it all was that it was accepted as conclusive evidence of death, and the poor widow received the pay- ments due to her. Applied chemistry is thus of great use, sometimes, in legal matters, although lawyers are not, as a rule, trained in such matters. Nitric acid, being one of the most important of modern chemicals, is manufactured in enormous quan- tities. It is stated that more than 100,000 tons are made annually enough to form a lake 200 yards square and 10 feet deep. At the present time, owing to the war, far greater quantities than this are being made. Nitric acid is absolutely indispensable for making dyes and explosives. The aniline dye industry worth millions of pounds annually would be non-existent without nitric acid. So also would the explosive industry. Almost every high modern explosive in some stage or other in its manufacture requires nitric acid. Thus nitro-glycerine the basis of dynamite, cordite, 28 MODERN CHEMISTRY AND ITS WONDERS blasting gelatine and the like is made (p. 59) by bringing together nitric acid and glycerine. Picric acid (the basis of lyddite, mellinite and the like) and trinitrotoluene, so important as the bursting charge of modern shells, are obtained by allowing nitric acid to react with phenol and toluene substances contained in coal tar. Ammonium nitrate a compound of nitric acid and ammonia is the base of most mining explosives. Therefore, deprive a nation of its nitric acid and you deprive it of its explosives and of its power of waging war. Until quite recently practically the only source of nitric acid was Chile saltpetre (sodium nitrate, NaNO 3 ). The acid was and still is obtained from this by heating it in iron boilers with concentrated sulphuric acid (oil of vitriol), when the following change takes place : NaNO 3 + H 2 SO 4 = NaHSO 4 + HNO 3 Sodium nitrate Sulphuric acid Sodium hydrogen sulphate Nitric acid The nitric acid which distils over is collected in earthen- ware vessels. Now, until quite recently, practically the world's whole supply of nitrates came overseas from a rainless and desert strip of land lying along the coasts of Chile and Peru ; it was long ago remarked that with all her strength Great Britain could be put out of commission in war times simply by cutting off her supply of nitrates from Chile. The same applied with even greater force to Germany and the Continent of Europe. In England at the time of writing the same fact holds to-day ; but in Germany new factors have come upon the scene, and she no longer depends to the same extent as formerly upon overseas imports of nitrates. Germany has begun to make her own nitrates and nitric acid. In my former book, Triumphs and Wonders of Modern Chemistry? 1 2nd ed., p. 196. SOME SIMPLE NITROGEN COMPOUNDS 29 I explained how in the atmosphere we have a practically inexhaustible supply of nitrogen about 4000 billion tons. Every square yard of land has about seven tons of nitrogen lying over it : but all this nitrogen is " free " and therefore useless for chemical purposes. We have to combine it or " fix it" as chemists say, before we can turn it into useful products. There are several ways of doing this. In the first place we can burn the nitrogen of the air directly to nitric acid simply by causing it to pass through a high tension electrical arc. How this was done was briefly indicated in my former book, but the subject has de- veloped since then and so, for completeness' sake, some additional details are here given. The various processes now in use for directly burning the air to nitric acid are shown diagrammatically in the accompanying drawing, which is taken from the writer's Chemical Lecture Diagrams. Fig. 1 shows a general view of the plant. A is the air compressor, which forces a steady stream of air into the electrical furnace B (which may be any of the types shown below). Here combination of nitrogen and oxygen occurs, nitric oxide, NO, being formed, thus : N 2 -fO 2 = 2NO ; and the gas at 800-1000 C., mixed with excess of air, passes into the cooling chamber C, and then along a series of pipes, D D, which traverse the interior of a boiler, F, and so heat it sufficiently to cause it to develop enough steam to work the pumps, &c. The gas, now cooled to about 50 C., enters a large oxidation chamber, G, where the nitric oxide, NO, finally unites with oxygen still present in the air to form nitrogen peroxide, NO 2 , thus: NO + O = NO 2 , and the chamber becomes filled with the brown fumes of this substance. Combination has not occurred before because in C the temperature was too high to permit of the existence of 30 MODERN CHEMISTRY AND ITS WONDERS NO 2 , as a high temperature decomposes it, thus: NO =NO + O. The nitrous fumes now pass along the AIR COMPRISE* FI6.I.GENERALVIEW OF PLANT 88B. 1C NO NO, DJ^ T- If OXIDATION FURHACC ST SAM BOILER CHAMBER FIG.3 BIRKEUND EYDE FURNACE SECTION FIG.2. BIRKELAND EYDE ELECTRIC FURNACE (DIAGRAMMATIC) E _IR ARC FLAME ItMPlOYEDBYTMS ;-ANIUN4SODA-rABKIK) FI6. 5. PAULING FURNACE Fl G . 4 . B I RKELAND-EYDC FURNACE EXTERNAL VIEW FIG. 2. Nitric acid from the atmosphere. pipe H I into the absorption tower K, where it meets with a descending stream of trickling water. This decomposes the nitrogen peroxide, forming a mix- SOME SIMPLE NITROGEN COMPOUNDS 31 ture of nitrous and nitric acid, thus : 2NO 2 -f H 2 O = HNO 2 + HNO 3 . This liquid can be drawn off and converted into pure nitric acid by driving warm air through it ; but more usually the acid liquids are allowed to flow into a series of tanks, L, rilled with moist limestone, which is converted into a mixture of calcium nitrate and -nitrite. If soda or potash is em- ployed as the neutralising medium, we get sodium or potassium nitrates produced. Fig. 2 is a diagrammatic sketch of the Birkeland-Eyde furnace. The electrodes consist of two copper pipes, A and B, kept cool by a current of water. They are con- nected with a high-tension powerful alternating current, which forms an arc between them. The arc is placed between the poles of a powerful electro-magnet, which then blows it out into a wheel-like disc of flame composed of burning oxygen and nitrogen. The whole is enclosed in a refractory casing, shown in section in fig. 3 and a general view in fig. 4. The section fig. 3 shows how air is blown in to feed the flame. The air enters at A A and passes in through holes in the refractory lining. The electric flame plays down the disc-like space C C, and the burnt gases come out at D and then pass away to the absorption plant, as indicated in fig. 1. E E are the wires of the electro-magnets. Fig. 4 shows how the Birkeland-Eyde furnace looks when viewed externally. Fig. 5 shows the Pauling arc flame. The main electrodes A and B are bent into the shape of a V, A H H being a section of one main electrode and B K K a section of the other. The base of the electrodes thus forms at M N a vertical slot, through which are intro- duced thin "lighting knives'' F F. These "knives" can be brought very close together by the screwing arrangement P P, and the arc, thus lighted at the 32 MODERN CHEMISTRY AND ITS WONDEF narrowest portion of the spark gap, shows a tendency rise up between H H and K K, owing mainly to 1 upward pull of the hot gases, but is interrupted at eve half period of the alternating current, only to be reform at the lowest and narrowest part of the electrod Through a nozzle, C, a stream of previously heated I air is blown upwards into the arc, causing the air diverge and form between the V-shaped main electroc a flame of burning O and N, sometimes a metre in leng Fig. 6 shows the furnace employed by the Badisc Anilin und Soda Fabrik, making use of the Schonherr ; flame. A A is an insulated high-tension electrode, 1 other electrode being the iron piping E E, into whi A A projects. An arc is thus formed between 1 electrode A A and the iron piping ; but a stream of is blown in peripherically at the base of the pipii through a series of orifices, X X, in such a way to cause a rotating movement in the tube E E, a a whirling flame of burning O and N to run up i tube E E E, which is cooled at the top by the wat cooling arrangement F F. The hot nitrous gases stre; away from E E, down the external pipes H H, and out into the plant for absorbing the nitrous fumes. 1 air enters the furnace at C, and is heated to a hi temperature before being blown into the arc (throu the orifices at X) by passing up the tube D D and do the tube B B, both of which are heated by the hot ga streaming away from the furnace. Now the main disadvantage of all processes of direc burning up the atmosphere is the very poor yield nitric acid for the power applied. Such processes c only come into extended use in lands where power cheap especially in lands rich in water power, wh is especially useful for the production of the elect current. Hence such processes have mainly develop SOME SIMPLE NITROGEN COMPOUNDS 33 in countries like Norway, Sweden and America, where very great waterfalls exist (see chap. VIII.). Quite recently, therefore, a sensation was made in the scientific world when it became known that nitric acid can be made quite cheaply from ammonia gas, NH g , and that the latter in its turn can be manufactured quite cheaply from atmospheric nitrogen and hydrogen, as we shall presently see. The process for turning ammonia into nitric acid was brought to perfection by the famous German chemist Ostwald. It is simplicity itself although many years of patient research were necessary before it was brought to commercial success. The ammonia gas is mixed with the requisite amount of oxygen gas and the whole is sent through tubes filled with a preparation of finely divided metallic platinum, which here acts as a catalyst. The temperature must be very carefully regulated, and when this is done, we get the ammonia quantitatively converted into nitric acid thus : NH 3 + 20 2 = HN0 3 + H 2 Ammonia Oxygen Nitric acid Water Thus Germany's power due entirely to scientific research of producing nitric acid quite cheaply from ammonia, renders her independent of the saltpetre beds of Chile for the supply of her explosives. In fact, were it not for the wonderful development of chemical science in Germany, it is quite safe to say that, encircled as she is by a ring of enemies, Germany would have been beaten to her knees in a few months. Her supplies of war necessities would have been utterly unequal to the demand. She could not, in fact, have undertaken the present terrible war at all. It is German science, even more than German armies, which has made her a menace to the neighbouring nations. It has given her such a c 34 MODERN CHEMISTRY AND ITS WONDERS powerful command over matter, that she can produce most of her own supplies. But this brings us back to our old friend ammonia y NH 3 , and we must now say a few words regarding this very important substance. Ammonia gas is lighter than air and very soluble in water, so that it must be collected by displacing the air out of a vessel as shown in the illustration (fig. 5). It may, of course, be collected over mercury. The gas thus obtained is colourless and invisible but possesses a most powerful smell. A single sniff .of it will bring tears to the eyes and almost suffocate one. Indeed death has been known to follow the accidental breathing of the vapour. Ammonia gas is so soluble in water that at C. over a thousand cubic feet of it will be condensed within a single cubic foot of water. The water becomes warm as the ammonia dissolves in it and extends so as to double its bulk. It is very probable that a chemical combination takes place, thus: NH 3 + H 2 0- NH 4 OH Ammonia Water Ammonium hydroxide This solubility of the gas may be shown by inverting a jar of it over water. This rushes up and completely fills it. A striking experiment is founded upon this fact. If a bottle filled with ammonia gas and fitted with a cork containing a tube which projects up inside the jar (fig. 3), be placed over water, the water will run up the jet and on reaching the end will squirt in a fountain into the interior of the jar until it is full of water. If the water be coloured red with litmus solution, this will turn blue within the jar owing to the action of ammonia, and we get a red fountain of water changing its colour to blue in a most striking way. The first drop of water which reaches the inside of the jar absorbs nearly all the ammonia in the neighbourhood and thus creates a partial SOME SIMPLE NITROGEN COMPOUNDS 35 vacuum inside. The external pressure of the air, pressing down with a force of 15 Ibs. per square inch, then forces the water into the vacuous vessel with such force that it squirts up as a regular fountain. The gas will not burn in air unless heated strongly. Chemically it combines with acids, neutralising them and FIG. 3. Solubility of ammonia in water. forming a series of most important compounds known as the ammonium salts, some of which are valuable manures. The solution of ammonia in water is what is termed a " base," because it has these properties and turns red litmus blue. Pressure and cold turn it into a colourless liquid which boils at -38-5 C. and freezes at - 77 C. to a mass of white transparent crystals. 36 MODERN CHEMISTRY AND ITS WONDERS Liquid ammonia, like water, absorbs much heat when allowed to evaporate, and is now used on a large scale for producing cold and manufacturing ice. This liquid ammonia possesses very powerful solvent properties, dis- solving as a rule those things which dissolve in water and in many other ways behaves like water. FIG. 4. Preparing ammonia by heating lime and ammonium chloride. Ammonia gas is easily prepared by heating together ammonium chloride and slaked lime, when the following change takes place : 2NH 4 C1 Ammonium chloride - Ca(OH) 2 Slaked lime (Calcium hydroxide) = CaCL + 2NH. 2H 2 Calcium chloride Ammonia Water SOME SIMPLE NITROGEN COMPOUNDS 37 As a matter of fact, very large amounts of ammonia are manufactured every year in this way from liquors which are formed when coal is distilled for the purpose of making coal gas. The coal contains a considerable amount of nitrogen, and much of this escapes in the form of ammoniacal liquors, which when collected and heated with lime evolve the ammonia as such. Usually, however, the evolved ammonia is absorbed by passing the gas into sulphuric acid, when the valuable ammonium sulphate is produced, thus : 2NH 3 + H 2 S0 4 = (NH 4 ) 2 S0 4 Ammonia Sulphuric acid Ammonium sulphate Thus, even in 1906 Great Britain produced about 290,000 tons of ammonium sulphate, and Germany about 235,000 tons. This substance found its main use, of course, for manurial purposes, as plants need for growth nitrogenous food quite as much as do animals. However such quantities, large as they may seem, are much too small to meet national needs. They are a mere drop in the ocean of the world's hunger for nitrogenous compounds. Consequently, a great sensation was produced in chemical circles in 1913 when it be- came known that two German chemists, namely Haber and Le' Rossignol, had succeeded in solving the problem of how to make free nitrogen and free hydrogen unite directly so as to form ammonia. Of course it had long been known that hydrogen and nitrogen will directly unite under suitable conditions. A simple experiment can be carried out to prove this. If we mix hydrogen and nitrogen gases together in the proportion of three volumes of hydrogen to one volume of nitrogen, and then pass a series of electrical sparks through the gaseous mixture, we notice that it 38 MODERN CHEMISTRY AND ITS WONDERS will contract and form the strongly smelling ammonia gas : N 2 + 3H 2 = 2NH Nitrogen Hydrogen Ammonia How electricity achieves this is not known. Perhaps the intense heat of the electrical spark shatters the hydrogen and nitrogen molecules into single atoms which then rush together to form ammonia molecules. The subject is, however, probably far more complex than this. It is known that under the influence of the electric discharge (which we must picture as a stream of tiny electrons flying like projectiles with a velocity of thousands of miles a second across the space occupied by the whirling gaseous molecules), centres of attraction appear in the gas, being probably composed of molecules or atoms which have captured many electrons. To them come streaming other molecules and group themselves in thousands around the centre to form complicated clusters. It is probably in these clustering groups of molecules that those collisions occur which give rise to the formation of ammonia molecules. Ultra-violet light will bring about the same result, but how or why these strange changes take place remains for the most part wrapt in mystery. However this may be, it is certain that any such method of producing ammonia is quite hopeless from a commercial standpoint the yield of ammonia is too bad. Now Haber and Le Rossignol set to work in another way. They made numerous experiments, and discovered that if they sent hot nitrogen and hydrogen through tubes containing finely divided metallic osmium or ura- nium the two gases will readily unite and the ammonia can be separated from the gases in quantities large enough to make the process a very profitable one. The SOME SIMPLE NITROGEN COMPOUNDS 39 metallic uranium or osmium act " catalytically " that is to say, they cause the union to take place without themselves undergoing any marked chemical change. Many such catalytic actions are known in chemistry, but how these " catalysts " work is not known. The process has been used technically on a large scale in Germany by the Badische Anilin und Soda Fabrik, and the whole process forms a really wonderful feat of scientific chemical engineering. Stupendous pressures are used the gaseous nitrogen and hydrogen being compressed to about 200 atmospheres 3000 Ibs. on the square inch and all leakage under this enormous pres- sure has been eliminated. Many of the details, however, are still kept secret, and it is known that works costing over 2,000,000 were being erected in Germany in 1913 for the production of ammonia on the larger scale. Owing to the dangerous pressures employed, it is stated that many of the working parts are buried in immense trenches so that the disastrous effects of an explosion will be minimised. The nitrogen is obtained in practically unlimited quantities by liquefying the air and separating the oxygen by fractional distillation, as ex- plained in my former book, Triumphs and Wonders of Modern Chemistry, p. 183. The hydrogen is obtained by the decomposition of coal gas or similar gases, or by passing steam over red-hot iron, or by passing water gas over red-hot lime, for in fact by modern methods hydrogen can be obtained in practically unlimited quantities and extremely cheaply. 1 The following diagram, fig. 5, taken from the author's Chemical Lecture Diagrams^ will explain the method em- ployed in making synthetic ammonia. The pump M forces a mixture of nitrogen and hydro- 1 The technical processes are explained at length in the author's work, Industrial Chemistry, vol. ii. 40 MODERN CHEMISTRY AND ITS WONDERS gen under a pressure of 200 atmospheres along the tube E E E into the vessel H, whence it passes out through X F F W through a drier, C (filled with soda lime), into the strong tube O P, as shown. A is an electric heater, whereby the gas passing along the inner tube S T is raised to a temperature of 800-1000 C., and then passes, while hot, through the contact substance at B (usually finely divided osmium or uranium), which is heated by the hot gas to about 500-600 C. Here combination between the hydrogen and nitrogen takes place, and ammonia is formed. The tube S T is thus kept hot by the gas streaming down it, the temperature being highest at S and decreasing as we proceed towards T. Therefore the cold entering gas, as it comes in by U and passes over the hot tube on its way towards S, naturally gets heated, and at the same time aids in cooling the tube from T to a, so that by the time the gas passes from U to S it is almost raised to the temperature of the furnace at S, whereas, as the heated gas passes down the tube S T, it is finally so chilled by the incoming gas at U that it issues at T with a temperature not much higher than the atmospheric. The interchange of heat is thus nearly perfect. The mixture of uncombined gas, together with the produced ammonia, passes along the tube N R, through the pump M, and then along the tube E E into the refrigerator H. H is surrounded by a vessel, L L,kept at a temperature of - 60 C. to - 70 C. by a mixture of alcohol and solid CO 2 ; and at this temperature the ammonia gas condenses to a liquid form, and may be drawn off at K. The cold, gaseous hydrogen and nitrogen, which remains uncondensed, passes away by X F F, and here meeting the entering gas coming down the interior tube E E chills it so considerably that it enters H at a temperature not far removed from that at which the ammonia condenses. At the same SOME SIMPLE NITROGEN COMPOUNDS 41 42 MODERN CHEMISTRY AND ITS WONDERS time the gas escaping along F F is heated almost to atmospheric temperature by the incoming gas, and so passes away through a drier, C (filled with soda lime), into U almost at atmospheric temperature. The production of ammonia in this way is fraught with tremendous economical consequences. Ammonium salts will become much cheaper than they have hitherto been, and so the price of nitrogenous manures will fall greatly. This will lead to a revolution in many branches of agriculture, and intensive farming will now be possible on a very large scale. Hence the capacity of the world to produce foodstuffs will increase greatly, so that a long era of prosperity should lie before the world if cheap and sufficient quantities of food have any influence on such matters. The manufacture of all sorts of expensive nitrogenous compounds, such as explosives, dyes, cellu- loid, photographic films, and so on, will also be enor- mously cheapened, and this in its turn will make other industries develop, and these will react one on the other so as to benefit trade and commerce in a way quite incalculable at present. Haber and Le Rossignol's process for producing synthetic ammonia represents the foundation of a world industry, whose evolution and development will profoundly modify the conditions of the human race. We must now say a few words about the compounds of nitrogen with oxygen the Oxides of Nitrogen. It has been mentioned in a previous chapter, nitrogen under the influence of an electrical discharge will burn in oxygen, producing oxides. There exist no less than five of these namely ; N 2 O, NO, NO 2 , N 2 O 3 , and N 2 O 5 . The first nitrogen monoxide, N 2 O is a colourless gas easily obtained by heating ammonium nitrate : NH 4 N0 3 = N 2 +2H 2 O Ammonium nitrate Nitrogen monoxide Water SOME SIMPLE NITROGEN COMPOUNDS 43 It is soluble in cold water but less so in hot. Burning bodies blaze in it almost as brightly as in oxygen gas itself. Its great peculiarity consists in the fact that when breathed it causes insensibility. While coming to, the patient will utter sounds like laughing. Hence the popular j-name -"laughing gas." It is much used by FIG. 6. Dentist administering nitrogen monoxide to a patient. dentists and doctors for minor surgical operations. If mixed with oxygen and breathed for a short time it will not cause insensibility but will intoxicate one like alcohol. Sir Henry Roscoe thus describes its effects on students working in a chemical laboratory : l "At the end of the session of laboratory work there 1 Life and Experiences, p. 35 (1906). 44 MODERN CHEMISTRY AND ITS WONDERS was held by the students what may be termed t a chemical saturnalia ' by the administration of nitrous oxide (nitrogen monoxide) to such of the laboratory inhabitants as desired to take it. I remember very well some ludicrous incidents, interesting in showing what varied effects the nitrous oxide intoxication pro- duces on different individuals. The Famulus of the laboratory was a Quilp-like creature, Williams by name. When under the influence of the gas he simply sat upon the coal box and made the most horrid series of grimaces that one could imagine. Watts (of dictionary fame) on the other hand when under its influence danced about in a high state of exhilaration, clicking his thumbs in great delight. A student of the name of Fox, a Quaker, and of course a man of peace, became terribly pugnacious, and chased us all round the laboratory. I remember fortunately hiding behind one of the doors in the furnace room, but he caught one of the excisemen, and, getting the head of the unfortunate man < into chancery/ inflicted considerable damage upon his person. It was all over in a few minutes, but it was deadly while it lasted. The astonishment of the peaceable Quaker, when he recovered, at the results of his onslaught was very amusing to all but the exciseman." The next oxide Nitric oxide, NO is also a colourless gas, much resembling nitrogen monoxide in general pro- perties. Its great peculiarity is that in air it turns red owing to its combining with oxygen, thus : 2NO + 2 = 2N0 2 Nitric oxide Oxygen Nitrogen peroxide (A red gas) It may be prepared by pouring strong nitric acid upon SOME SIMPLE NITROGEN COMPOUNDS 45 copper strips or shavings, and, being insoluble, may be collected over water ; 3Cu + 8HNO 3 = 2NO + 3Cu(NO 3 ) 2 + H 2 O Copper Nitric acid Nitric oxide Copper nitrate Water The gas is poisonous, combining with the haemoglobin, the red colouring matter of the blood, to form a compound which prevents it from fulfilling its function of oxygen carrier. The gas is even more deadly than carbon monoxide, which combines in a similar way with the Wood. The substance has been known to explode. Indeed some years ago a quantity of the gas stored up in an iron structure in a chemical works exploded when a workman merely turned a tap, and, blowing the apparatus to pieces, killed the unfortunate man. It was probably re- solved into free nitrogen and oxygen. The third oxide Nitrogen peroxide, NO 2 is, under ordinary circumstances, a red gas. It exists, however, in two forms. Below 10 C. it forms a colourless liquid having the formula N 2 O 4 . Above this temperature it begins to break down into N'O 2 , changing colour as it does so, and becoming dark red. The red fumes noticed when nitric acid or nitrates are heated are due to the forma- tion of this substance. It may be prepared by heating lead nitrate. Pb(N0 3 ) 2 = PbO + 2N0 2 + 2 Lead nitrate Lead monoxide Nitrogen peroxide Oxygen The substance is a terrible and insidious poison. Many a man has breathed it without at the time noticing any bad effects, but after some hours or even days a pain may develop in the region of the lungs, a violent in- flammation may set in, and death through pneumonia follow. The reason is that the water in the lungs decom- 46 MODERN CHEMISTRY AND ITS WONDERS poses it, forming nitric and nitrous acids, both terribly corrosive, and these cause wounds in the tissues and set up the inflammation. 2N0 2 + H 2 0=HN0 3 + HN0 2 Nitrogen peroxide Water Nitric acid Nitrous acid This fact is rather interesting, because when modern explosives detonate large amounts of nitrogen oxides are evolved and soldiers breathing such fumes are very liable fatally to injure their lungs. (See p. 78.) Of the remaining oxides, Nitrogen trioxide, N 2 O 3 , is a very unstable blue liquid, which freezes to green crystals, and above - 20 C. it decomposes to NO and NO 2 . While nitrogen pentoxide, N 2 O 5 , is a colourless solid, which ex- plodes when suddenly heated, and dissolves in water, pro- ducing nitric acid : It may be produced by distilling strong nitric acid with phosphorus pentoxide. For ages in the past a terrible and mysterious poison now called Hydrocyanic or Prussic acid has been known to exist. It was extracted from crushed peach stones or leaves, by allowing them to remain soaked in water for some time and then distilling the liquor. The first part of the liquor which distilled over contained the poison. In ancient Egypt some four thousand years ago it was used for putting people to death. Thus on a papyrus pre- served at the Louvre, M. Duteil read, " Pronounce not the name of I. A. U., under the penalty of the peach!" in which dark threat, without doubt, lurks the meaning that anyone who revealed the religious mysteries of the priests would be put to death by waters distilled from the peach. "That the priests actually distilled the peach SOME SIMPLE NITROGEN COMPOUNDS 47 leaves," says Blyth, 1 " has been doubted by those who consider the art of distilling a modern invention ; but this process was well known to adepts of the third and fourth centuries, and there is no inherent improbability in the supposition that the Egyptians practised it. From the Egyptians the knowledge of the deadly drink appears to have passed to the Romans, for, although not expressly mentioned, yet the fact that, in the reign of Tiberius, a Roman knight, accused of high treason, swallowed a poison and fell dead at the feet of the senators, is wholly inexplic- able, unless it be allowed that the fatal dose was prussic acid, and that in a tolerably concentrated form." Indeed it is believed that this was the actual poison used by Nero to get rid of his brother Britannicus, for the details of this tragedy have been recorded with some minuteness. " It was the custom of the Romans to drink hot water, a draught nauseous enough to us, but, from fashion or habit, considered by them a luxury, and, as no two men's tastes are alike, great skill was shown by the slaves in bringing the water to exactly the degree of heat which their respective masters found agreeable. The children of the imperial house, with others of the great Roman families, sat at the banquets at a smaller side table, while their parents reclined at the larger. A slave brings hot water to Britannicus ; it is too hot ; Britannicus refuses it. The slave adds cold water ; and it is this cold water which is supposed to have been poisoned: in any case, Britannicus had no sooner drunk of it than he lost voice and respiration. Agrippina, his mother, was struck with terror, as well as Octavia, his sister. Nero, the author of the crime, looks coldly on, saying that such fits often happened to him in infancy without evil result ; and after 1 Poisons : Their Effects and Detection, by A. W. Blyth, p. 2. Published by Griffin & Co. 48 MODERN CHEMISTRY AND ITS WONDERS a few moments' silence, the banquet goes on as before." l In the light of modern science we know that the poison must have been either prussic acid or one of its salts. The effects, indeed, of the poison are appalling in their suddenness. A few drops placed in the eye of a dog kill it in thirty seconds. A man has been known to swallow a quantity of the acid, stagger a few paces, and fall dead without a sound or convulsion. Usually, how- ever, the poisoned person falls to the ground in convul- sions, and dies in a few minutes. This terrible substance is known now to be a simple compound of hydrogen, carbon, and nitrogen, having the formula HCN. The pure acid when free from water is a colourless extremely volatile liquid. It has a very peculiar peach-blossom odour and is a strong acid. Usually it is met with dissolved in large excess of water. It may be prepared by distilling any cyanide with dilute sulphuric acid, and condensing the evolved gas in a suitable glass vessel in water. Yet on account of its terribly poisonous nature (a mere sniff of the vapour having had fatal results) only very skilled chemists should undertake its preparation. It seems almost incredible that the famous Swedish chemist Scheele, who first pre- pared it pure by distilling potassium ferrocyanide with sulphuric acid in 1782, should have been totally unaware that he was dealing with the most powerful of all known poisons. Thus we read with astonishment that he smelt and tasted it, and did various other experiments with it without ill effects. Free prussic acid occurs in the unripe berries of certain plants. It there serves as a protective means to prevent them from being eaten while still unripe by birds. The curious part of the matter is that as soon as some of these berries are ripe, the prussic acid disappears, 1 Blyth, loc. cit., p. 6. SOME SIMPLE NITROGEN COMPOUNDS 49 as there is no longer need of protection. In many plants and natural oils, especially in bitter almonds, it occurs not free but combined with a sugar, forming a complex compound called amygdalin. By boiling with acids, or even on prolonged standing with water in the presence of certain ferments or enzymes, the acid is set free. The salts of the acid form a very interesting and im- portant class of bodies, which, however, we cannot discuss further here. Before concluding this chapter a few words must be said regarding an interesting gaseous compound of nitrogen called Cyanogen. This in some respects is allied to hydro- cyanic acid, having the formula C 2 N 2 , although it is a colourless substance not having any acid properties. It was discovered by Gay-Lussac about a hundred years ago, who prepared it by heating the cyanides of gold, silver, and mercury, thus : Hg(CN) 2 = Hg + C 2 N 2 Mercury cyanide Mercury Cyanogen The mercury salt is placed in a hard glass tube fitted with a cork and gas-delivery tube. At a dull red heat the gas is rapidly evolved and may be collected over mercury, being somewhat soluble in water. The colourless gas seen to collect over the mercury possesses a smell somewhat like that of peach-blossoms, and when a light is applied to the mouth of the vessel containing it, it is seen to burn with a magnificent purple flame. It is terribly poisonous, a breath or two of it being fatal. At the very highest temperatures carbon and nitrogen appear capable of directly uniting, cyanogen, for example, appearing in the gases evolved from blast furnaces. It is supposed by some authors that it exists on the sun. In eclipses of the sun Hale has observed cyanogen gas floating immediately above the layer of D 50 MODERN CHEMISTRY AND ITS WONDERS white hot clouds which girdle the sun. Probably it occurs in far greater masses beneath these clouds, where it is in- accessible to observation. If it thus occurs in the sun it must probably have existed once upon a time in the primeval atmosphere of the earth. It certainly occurs in comets. In the tail of the last comet (Comet More- house) the spectroscope discovered traces of this deadly gas, and it has been suggested that the passage of a large comet through the solar system may cause such an irruption of this substance into the earth's atmosphere from external space that the whole human race would be poisoned. 1 Although not, I suppose, inconceivable, such an event is very improbable, the largest comet yet discovered bearing with it a quantity of matter far too small appreciably to affect the earth. However, it is by no means impossible that in space there exist worlds whose atmospheres contain large amounts of this gas, and whose seas are impregnated with prussic acid. The faintest breath of their atmospheres, and the slightest gulp of their waters would instantly prove fatal to any creature built on lines similar to those found upon the earth. 1 Several novels have been written in which the supposition is made that in its journey through space the earth dashes into such poisonous vapour, which kills off everything except the heroes and heroines of the story, who have an exciting time exploring the dead world and starting it anew. CHAPTER III THE ROMANCE OF EXPLOSIVES HUMAN civilisation is very old, so old that its very beginnings are lost in the mists of antiquity. Thousands of years before London or even Troy was founded, there existed huge world-cities, with their swarming millions of inhabitants, their long broad paved streets, their countless shops and stately palaces. Such indeed were Babylon, Nineveh, Ur and Nippur, the ancient wonder cities of Mesopotamia, some four thousand years ago. Their remains, buried under the dust mounds of ages, are now being laboriously excavated. Indeed the modern traveller when passing over the desolate and silent wastes of sand which now cover their ruins can scarcely realise that he is standing on a place where thousands of years ago reigned the most intense human activity. He can stand on the very spot where " Once Babylon, by beauty tenanted, In pleasure palaces and walks of pride, Like a great scarlet flower reared her head, Drank to the sun, and laughed, and sinned, and died." But all that he will see of her one-time mighty fortifi- cations and colossal buildings, which towered up into the air to the height of 600 feet, are a few unsightly mounds of earth. Centuries before Christ, great commercial cities like Tyre, Sidon, and Carthage were built of rows of streets of stately, six-storied, stone houses, while thousands of 51 52 MODERN CHEMISTRY AND ITS WONDERS trading ships rode at anchor in their harbours or were moored along their broad, busy quays. Civilisation reached a high level in ancient Egypt. Some of the engineering works carried out by the Egyptians still remain unsurpassed, the wonder of the modern world. Crete, thousands of years before our era, was the theatre of a wonderful civilisation, the very memory of which had faded like a dream from the memory of men until, a few years ago, the ruins of great palaces were unearthed, whose charred remains tell us of wars unrecorded and forgotten in which this civilisa- tion perished. Ages later, and still in the memory of all, arose and spread the splendid civilisations of Greece and Rome. America, too, even in very early times, seems to have from time to time witnessed the periodical rise and fall of native civilisations. A common fate overtook these old civilisations. One after another they perished, overwhelmed by armies of warlike savages. Time after time this has happened, not only in Asia, but also in Europe and America. Every time settled life and pro- gress began in any region of the world, when towns began to grow up, wealth and trade develop, and plenty and prosperity to smile throughout the land, then thrift- less savages in neighbouring districts, scorning to obtain by patient labour what might be taken by force of arms, came pouring in upon the bright spot, and usually suc- ceeded in destroying so completely the beginnings of civilisation in these regions, that we are often ignorant to this very day that they ever existed. The world's history or rather that fragment of it with which we are acquainted is one vast tragedy. And the reason is simple enough. A civilised man is not and never will be a match physically for savages living under wilder and harder conditions. The very conditions of civilisa- THE ROMANCE OF EXPLOSIVES 53 tion set a premium upon a high intelligence and a weak muscle, and the process of evolution in a very short time produces a type of man corresponding to this want. But among savages intellect is at a discount. It is the fighting man, the man with strength and courage, who is esteemed and valued, and consequently produced by the conditions of life under which he exists. Unless, there- fore, a civilised state can compensate the physical dis- advantages of its warriors by artificial aids such as a superior organisation, powerful fortifications, and offen- sive death-dealing machinery, sooner or later this state is bound to perish in hand-to-hand conflicts with ruder and less civilised nations ; and thus the advances it has made in the art of life are all swept away again. This being so, we may well inquire whether the modern European civilisation will also perish in the same way ? We believe not. It is possible that our civilisation will suffer a slow process of internal decay as the result of the spread of some religious mania, such as has happened in the East time after time, and in the West once at least ; but violent, abrupt dissolution at the hands of savages is now unthink- able. And the reason is simple. Behind each civilised man now stands a power a million times mightier than the strongest arm that ever drew a sword or hurled a spear the terrible power of modern explosives. The bravest savage is as defenceless as a rabbit before civilised man with his lyddite shells and quick-firing guns. Un- civilised races can manufacture swords and spears and arrows of the materials found abundantly about them. But the manufacture of explosives and of arms of precision is utterly beyond their power ; for their production re- quires a knowledge of chemistry and of engineering science such as is unattainable by any uncivilised people. Indeed a people arriving at such knowledge must neces- sarily attain civilisation at the same time. Under modern 54 MODERN CHEMISTRY AND ITS WONDERS conditions a civilised race can only be overcome by a civilised race. Nay, more ; we may well doubt whether at the present time a civilised race can be overcome even by a civilised race. A nation like Germany, governed by military despots drunk with an imaginary superiority, may try to overrun the world. But her only chance was to take the world by surprise, to deliver a swift, assassin-like blow in the midst of smiling peace, and overwhelm the other nations while these were unprepared for war. Give but a breathing time, and civilisation puts such terrible defensive weapons in the hands of the defenders, and such mighty economic forces into motion, that such efforts are brought to nought. Napoleon took fifteen years to kill a million men ; Kaiser William the Mad, in his attempt to wreck a continent, killed two millions of men in twelve months, and into the vortex of the titanic struggle sucked thirty millions of armed men. Such are the forces which modern civilisation opposes to those who try the methods of savages and endeavour to take by force that which is not theirs by right of labour. Modern science has rendered as true now as ever it was, the old, old saying that " he that taketh the sword shall perish by the sword." Thus we owe our safety to explosives, and in- directly to the chemist who produces them. It was said of old that the pen is mightier than the sword. We can now say with truth that the balance of the chemist is mightier than either. The nation that leads in chemistry leads in all other things, for upon this science there depend not only the means of pro- ducing metals for making machinery and tools, but also the production of materials from which are made clothes, books, inks, paint, dyes, medicines, and fire itself in a word, all that distinguishes our life from that of prehistoric savages. THE ROMANCE OF EXPLOSIVES 55 But here the reader will require to know what we mean by an " explosive." Any body which will suddenly expand and exert great force in so doing may, in a sense, be called explosive. Even such a harmless liquid as water can be made to act as a powerful explosive. The most terrific natural explosions which occur on the earth are caused by it. When water is brought into contact with white- or red-hot material it is suddenly converted into steam which may occupy several thousand times the volume of water from which it was produced, and if restrained from so doing will exert an enormous force. The terrible volcanic explosions which occur from time to time, and fill the world with awe and terror, are due, as a rule, to water coming into contact with the white-hot matter in the interior of the earth. Whole mountains and islands have by this means been blown into the air with a tremendous crash. Thus at Krakatoa in 1883 a whole mountain, forming more than a cubic mile of solid rock, was hurled into the air. The vast thunder of the explosion was heard nearly 2000 miles away, while windows were shattered by the mighty sound-waves at a distance of 150 miles! In comparison with this, the most awful of artificial explosions produced by modern high explosives seem quite puny. Thus in 1896 some 55 tons of blasting gelatine were being unloaded from a railway train at Johannesburg in South Africa, when it exploded as the result of an end-on collision. The town was startled by the sound of a titanic thunderclap, and looking upwards saw a sheet of flame accompanied by a cloud of flying debris ascending to the sky. Rushing to the spot, the townspeople found that a crater 300 feet long, 65 feet broad, and 30 feet deep had been produced in the soft ground, while every building within a radius of 1000 yards was either blown down or badly shattered. 56 MODERN CHEMISTRY AND ITS WONDERS About 30 ; 000 tons of material had been blown into the air. In 1893 the Hudson River Palisades were blown up at Fort Lee, and there 2 tons of dynamite, placed in a chamber in the rock, brought down 100,000 tons of rock. In the same year 2^ tons of dynamite, placed in chambers in a dyke at the Dinoric quarries at Llanberis, blew up 180,000 tons of rock; while at Talcen Mahr in 1895, 7 tons of powder poured into two shafts overthrew nearly 200,000 tons of material. Yet what are these results when compared with the explosion which at Krakatoa blew into the air some seven thousand million tons of rock and earth ! All modern explosives are solid or liquid substances which are capable of suddenly liberating large quantities of gas as the result of extremely rapid chemical action. These gases set up a tremendous pressure, and so blow out the bullet from the gun with enormous force in exactly the same way that the compressed air of a boy's air-gun does. The explosion, or the sudden conversion of a solid or liquid into gas, is effected by the application of heat, electricity, or simple percussion. The explosive best known to us all is Gunpowder. This consists of : Potassium Nitrate, KNO 3 . . 75 parts Charcoal, C . . . . 15 Sulphur, S 10 The finely-powdered materials are thoroughly mixed together in gun-metal or copper drums, having blades in the interior capable of working in the opposite direction to that in which the drum itself is travelling. After passing through a sieve the mixture is then ground under heavy metal rollers, subjected to hydraulic pressure, and then THE ROMANCE OF EXPLOSIVES 57 broken up into a form suitable for the particular purpose for which the powder is intended. The explosion is due to the fact that the elements of the potassium nitrate are dissociated by heat, gaseous oxygen and nitrogen being set free. The nascent oxygen combines with the carbon to form the gases carbon mon- oxide (2C + O 2 = 2CO) and carbon dioxide (C + O 2 = CO 2 ). The sulphur should unite with the potassium to form solid sulphide of potassium according to the equation : 2KNO, + S + 3C = 3CO 2 o Potassium nitrate Sulphur Carbon Carbon dioxide (saltpetre) + K 2 S + N 2 Potassium Nitrogen sulphide But as a rule it unites with some oxygen, producing the gas sulphur dioxide (S + O 2 =SO 2 ). The gases formed by the explosion of a given bulk of gunpowder occupy about 300 times the bulk of the powder at ordinary tempera- tures. The enormous heat produced by the sudden in- flammation expands these gases many times further. To this expansion the explosive force is due. The force set up may be reckoned as some hundreds of tons per square inch. Moreover, as the powder burns rapidly this pressure is suddenly applied, and has all the effect of a tremendous blow. The chamber in which the bullet is confined gives way at its weakest point. Hence the bullet yields before the breech, and is hurled with a mighty force from the barrel. This is not always the case : fearful accidents sometimes occur when the ball has been too tightly wedged, or when the metal of the breech is weak. In the atomic world we must picture the explosion as consisting in millions upon millions of gaseous molecules bursting forth from the flaming surface of the powder 58 MODERN CHEMISTRY AND ITS WONDERS and flying swiftly against the bullet, whirling as they fly with incredible velocities. Then, just as one billiard ball imparts motion to another, so also do each of the myriads of molecules imparts theirs to the projectile. The motion imparted by a single molecule may be as nothing, yet the accumulated effect of untold millions of impacts is stupendous. The projectile acquires an ever- increasing motion, until it finally rushes forth from the barrel and flies shrieking through the air on its errand of destruction. The whole complex change, the sudden shattering of countless millions of atomic systems, passes in a flash beneath our eyes. Yet, as I have pointed out in my former book, 1 a single second is a vast interval of time in the atomic universe, during which the atoms have ample time to carry out countless billions of minute evolutions ; consequently the bright flash of an explosion is to an atom no swift change, but in reality betokens the slow and orderly passing of one atomic universe into another. The old black gunpowder is now rapidly passing away, having been almost entirely superseded by other explo- sives, as we shall presently see. The smoke which it pro- duces when fired contains more than 50 per cent, of the total weight of the powder, and is thrown out as solid matter to foul the atmosphere, becloud the gunner, and make his situation a conspicuous target for the enemy. The modern smokeless powders are free from these defects. The effects producible by gunpowder, mighty as they are, fade into insignificance when compared with those producible from certain modern " high " explosives such as dynamite or nitro-glycerine, picric acid, and mercury fulminate. The starting-point in the manufacture of dynamite is glycerine. I suppose that everyone is 1 Triumphs and Wonders of Modern Chemistry, 2nd ed., p. 6Q. THE ROMANCE OF EXPLOSIVES 59 acquainted with this clear, oily, and sweet-tasting liquid, and, indeed many of us have eaten it in honey, for it is often used for adulterating this article by unscrupulous dealers. Glycerine is obtained in very large quantities as a secondary product in the manufacture of soap and candles from oil and fats, being produced by the action of high-pressure steam or boiling alkalies upon these substances. In order to make nitro-glycerine, the glycerine is sprayed in a very fine stream into a leaden tank (called a "nitrator ") containing strong nitric acid, rendered more active by being mixed with sulphuric acid, and kept cold by a stream of cold water circulating through leaden coils in the interior of the vessel. In all these dangerous processes stirring is required, and since air is the most easy and frictionless means of agitating a liquid, a stream of this is allowed to bubble up from perforated pipes placed in the tank. There is no apparent change, for pure nitro-glycerine resembles glycerine itself very closely in appearance ; nevertheless the following change has occurred : C 3 H 5 (0 . N0 2 ) 3 + 3H 2 Glycerine Nitric acid Nitro-glycerine Water What has happened is that three hydrogen atoms from the glycerine molecule have been displaced by the introduction of three NO 2 groups from the nitric acid. As soon as the chemical change is ended the nitro- glycerine must be separated from the nitric acid and then washed until it is completely free from adhering acid. This is carried out as follows. The leaden tank in which the reaction takes place is provided with a narrow conical top as seen in our illustration (Plate 1). When the action is over, waste acid from a previous charge is run in at the bottom and displaces the nitro-glycerine upwards, and 60 MODERN CHEMISTRY AND ITS WONDERS this overflows by way of an outlet from the narrow top of the nitrator. This top chamber is a closed compart- ment with a glass window in the narrow overflow face. The nitro-glycerine containing a large volume of water and acid runs over into a first washing vessel, called a " forewash," seen between the two nitrators in Plate 1, the flow being stopped when the waste acid has risen to the sight window. In the first wash tank the liquid is washed with a copious supply of water agitated by a rapid stream of air kept bubbling through it in order to free it from acid. The water is skimmed off by an indiarubber pipe, and the nitro-glycerine is then run into a second vessel containing a large volume of water, seen in our illustra- tion, Plate 1, between the two stairways, and is then washed again. Next it runs away through a gutter and enters the final wash-house, shown in Plate 2. In this the heavy, oily nitro-glycerine is washed with alkaline water, with softened warm water, and with softened cold water, and finally is drained off and collected. The object of this extremely thorough washing is to prevent the prepared stuff from spontaneously decom- posing in use, the slightest trace of acid left in it having been known to cause terrible disasters through premature explosion. The nitro-glycerine is then freed from moisture by being filtered through salt, which, being unaffected by the explosive liquid, sucks out of it the last of its moisture, thus serving both as a filter and a dryer. All waste water goes to a large tank in a further house, and is run through a labyrinth to separate any nitro-glycerine that it still contains. The mud which settles in the tank is run with the waste water into a pond at some distance, and at brief intervals a cartridge is fired in the bottom of that pond in order to blow up and destroy any traces of nitro-glycerine which may accumulate there. A visit to a large explosive works is well worth making. From Cassier's Magazine. Nitrators Forewash Nitrators PLATE 1. Manufacture of Nitro-glycerine. From Cassier's Magazine. PLATE 2. Interior of the Washing House of a Nitro-glycerine plant. THE ROMANCE OF EXPLOSIVES 61 The most elaborate precautions are taken to avoid disaster. The buildings are separated by wide intervals, and are buried deep in the earth and surrounded by great earthworks in order to minimise the effects of any explo- sion. The workmen move silently about clad in soft felt shoes, for boots containing nails might cause a percussion and result in a terrible disaster. In each building very few men are employed, so that any culpable carelessness on the part of a workman will result in the loss of only two or three lives at most. In one room you will see the dangerous nitro-glycerine being produced by the hundredweight. By the side of the tank containing the nitric and sulphuric acids, into which the glycerine is steadily pouring, you will see a workman sitting intently watching a thermometer. By him is an apparatus for signalling alarm to neighbouring buildings. Anything going wrong with the charge in the nitrator will manifest itself in a rapid rise of temperature. The utmost upper limit of temperature allowable is 25 C. (77 F.), and if the rise continues a few degrees above this the whole charge may explode and blow the whole building into the air. So the workman sits with his hand on a lever, ready in an instant, by means of a single move- ment of it, to turn off the stream of glycerine and dis- charge the contents of the nitrator into a deep tank of cold water, situated under the foundations of the house. Here it is flooded and all danger is at an end. How dangerous is the operation of making nitro- glycerine, and how easy the slightest carelessness of the workmen is visited by the supreme penalty of death, may be seen from the case of the explosion at Hayle, which occurred on January 5, 1904, at 10.55 A.M. At the time of the explosion nitro-glycerine was flowing down a gutter from the precipitating house to the washing- house, which were separated by an interval of about a 62 MODERN CHEMISTRY AND ITS WONDERS quarter of a mile. What exactly happened will now never be known, but it is believed that the single workman who was in the former building clumsily dropped the heavy leaden lid of one of the tanks. The concussion was sufficient to explode the whole charge, which first blew into fragments the precipitating house, instantly killing the man, and then flashing down the gutter, the explosion entered the washing-house, killing the three men working there, and hurling the building into the air. The thunder of the explosion was heard over an area of 3000 square miles, extending even so far as Exeter, some 90 miles away. The effects of the explosion were visible for several miles around the works, chiefly in the breakage of glass. Thus at St. Ives, no less than four miles away, some 200 worth of glass windows were shattered, many being blown entirely out. And here a curious thing was noticed, a phenomenon which accompanies most terrific explosions. The windows, especially in the houses facing the works, were blown, not inwards but outwards. The effect of an explosion at a distance is apparently to project the atmosphere vertically and produce a partial vacuum around, so that the air inside a vacuum-surrounded house simply bursts it open and blows its windows outwards. But this reminds me of the exciting time which a public school has just come through safely. The crisis came suddenly during the chemistry lesson of one of the higher classes. One of the boys quietly remarked to the master : " Please, sir, I have made a pint of nitro-glycerine," and he held up proudly for the master to see a beaker filled with a pale yellow liquid. The class stared at the beaker in horrified amazement. The master paled. There was enough of the deadly explosive to blow the whole school down, and half the town with it. "Good God!" said the master, " how did THE ROMANCE OF EXPLOSIVES 63 you make it?" "Oh/ 1 said the boy, "I just poured a pint of glycerine into a mixture of strong nitric and sulphuric acid." The master carefully approached the beaker and gingerly carried it to a cupboard. Little work was done during the rest of the lesson. Everyone walked about on tip-toes, and none ventured near the cupboard where the terrible jar reposed. After the lesson the news spread like wildfire. Everyone had visions of the buildings flying skyward like a fiery rocket. At every un- usual sound boys and masters jumped. The sudden slam- ming of a door sent a shudder through the whole school. Late in the afternoon the chemistry master stole silently from the school, with the beaker in his hand. Gingerly he picked his way up the main-street of the town in a zigzag path to avoid the possibility of collision with passers-by. Arriving at the playing grounds, he distributed the nitro-glycerine in remote parts of the grounds. When he returned the school breathed a sigh of relief, and set up the master as a lifelong hero. Mean- while the enthusiastic young experimenter was sternly summoned to interview the infuriated head . . . but here we will stop. Instead of dwelling on the painful scene which ensued, let us discuss the properties of nitro-glycerine. Nitro-glycerine is a heavy, colourless oil which, like the glycerine from which it is derived, tastes sweet. It is very poisonous ; in large quantities it acts like strychnine, and causes death in a few minutes ; but in small quantities it is a powerful medicine for stimulating the heart. It soaks into most substances in a most extraordinary manner. Indeed if placed on the skin it will soak through into the blood, causing giddiness and severe heart trouble. After a time, however, workmen get used to it, and indeed actually knead the glycerine into other substances by the hand, as we shall presently see. After the terrible accidents that have happened the 64 MODERN CHEMISTRY AND ITS WONDERS reader will be surprised to hear that nitro-glycerine does not readily explode. It is not nearly so explosive as gunpowder. In fact the flame of a match can be quenched in it without danger. If we apply a light to it, the oil will burn quietly with a smoky flame. If poured from an open vessel on to a fire the liquid usually blazes up without explosion. In fact it is only when suddenly heated, or when subjected to a violent shock, such as that caused by the explosion of a small charge of fulminating mercury, that it will explode. But when the substance does explode it goes off with terrific violence, shattering the stoutest structures into fragments. Its explosive force is estimated at eight to ten times that of the same weight of gunpowder. Nitro-glycerine has several properties which make it dangerous to use as such. For example, it freezes between 4 and 5 C. into a crystalline solid which must be thawed again before using by placing in warm water. When solid it is much more liable to explosion by simple per- cussion than when liquid. At Hirschberg a mining overseer was killed by the explosion of some frozen nitro-glycerine which he attempted to break into smaller pieces with a pickaxe. Like water, the nitro-glycerine expands in freezing, and may thus burst the vessel con- taining it in the same way that freezing water sometimes bursts water-pipes. Indeed this was the cause of a terrible accident some years ago. A box of nitro-glycerine was being sent to some mines and was lying in the office of a luggage company waiting to be fetched away. The cold had caused the substance to freeze and burst its packing. In the warm office it again melted and, unluckily for him, one of the office boys observed a yellowish liquid oozing from under the lid. Being of an industrious nature he at once fetched a hammer and nails and began to fasten the lid on more securely, when, with THE ROMANCE OF EXPLOSIVES 65 a flash like lightning and a roar like a vast thunder peal, the box exploded, shattering the whole office and causing the great building to reel and almost collapse. When the dust of fallen masonry and the smoke had cleared away, the horrified searchers discovered that some thirty people had been blown to pieces. No trace of the unfortunate office boy was ever found again. This disaster shows that nitro-glycerine is in some respects very dangerous to store and to transport. Indeed when it first began to be manufactured by Mr. Nobel a Swedish engineer no railway or ship company could be induced to accept the danger of conveying it. Mr. Nobel was actually on the point of abandoning its manufacture when a fortunate accident revealed to him a method of making it transportable. One day when unloading a waggon containing a number of jars of nitro-glycerine packed in sand to prevent breakage, it was observed that a jar had fractured and that the nitro-glycerine had soaked right into the sand, just as ink soaks into blotting paper. The sand was observed to have the same powerful explosive properties as the pure nitro-glycerine, but was far safer, and being in a compact form, far easier to transport. The old " Kieselguhr Dynamite," in fact, is merely sand soaked in nitro-glycerine. Ordinary sand, however, is not used but a fine sort called " Kieselguhr," which is really nothing else- than the skeletons of innumerable myriads of tiny organisms, and will absorb no less than three times its weight of nitro-glycerine. The quantity absorbed, however, must be always less than the capillarity of the cellular diatoms enables them easily to retain without drip or overflow. Kieselguhr fully charged with nitro-glycerine is as dangerous as the unabsorbed liquid itself. Now kieselguhr (a variety of sand) is in itself an inert substance and so reduces the effective action of the ex- plosive base nitro-glycerine. 66 MODERN CHEMISTRY AND ITS WONDERS A great advance was made when, instead of inert kieselguhr, other absorbants for the nitro-glycerine were used which are themselves explosives. One of the most powerful explosives in use is of this nature and is called "blasting gelatine." It is, in effect, a solution of nitro- glycerine in a kind of gun-cotton called collodion cotton (made by soaking cotton in a mixture of nitric and sulphuric acid). It is made by mixing together 7 to 10 per cent, of collodion cotton with 93-90 per cent, of liquid nitro-glycerine at a temperature of 40 C. Solution takes place and on cooling an amber-coloured, translucent, elastic mass is produced. When saltpetre and wood meal are kneaded into the mixture we get the explosive known as Gelatine dynamite or gelignite. These dynamites have so far displaced the old " kieselguhr dynamite " that the latter formed in 1909 only 0'4 per cent, of the total amount of explosives used in mines and explosives in Great Britain. And now a few words on what dynamite has done for civilisation. Modern times have been distinguished by the carrying through of gigantic engineering. operations ; it is quite safe to say that without the employment of high explosives these could never have been achieved. Tunnelling operations have become quite simple, dynamite cartridges enabling men to blast their way right through the hearts of mountains, while dynamite makes the con- struction of great canals an easy matter ; the rocks and earth in the way are simply shattered by dynamite ex- plosions and the debris is then carted away by mechani- cal appliances. Consequently once any great engineering feat such for example as the making of the Panama Canal is decided upon, the price of dynamite and the raw product glycerine from which it is obtained at once goes up with a bound, as the demand for explosives exceeds the supply. Now these great engineering operations have all one THE ROMANCE OF EXPLOSIVES 67 object in view, and that is the speeding up of communica- tion between one part of the world and another ; and so dynamite, perhaps more than any other agent, has knit the world into a closely connected civilised whole. Methods of quick transit of persons, inventions, news, and mer- chandise from one part of the world to another have done more to bring universal peace and prosperity into the world than any other influence, and as this has in the main been made possible by engineers who in their turn could only do their work by using high explosives, the inventor of dynamite probably has been one of the greatest benefactors to humanity. Thousands of tons of dynamite are made yearly and used for blasting purposes. In using gunpowder for blasting it is necessary tightly to confine it, by what is called " tamping," in a hole prepared for it in the rock. In fact if gunpowder was exploded on an iron plate in the open air the disruptive effect would be nil. It must be confined. But this is not so with dynamite or nitro- glycerine. They exert their greatest force in the direction of those points in actual contact with them. Hence if a small amount of dynamite be merely placed on the top of a large boulder rock or on an iron plate, and be absolutely unconfined in any way, then on exploding the dynamite the rock or plate will be shattered into a thousand fragments. Hence dynamite, made up into small tin cartridges for convenience, is merely placed in the drill holes without tamping of any kind. Sometimes the liquid nitro-glycerine itself has been poured into the hole and then a little water poured on top is the only means used to confine it. This makes nitro-glycerine rather a favourite explosive for burglars who wish to blow open safes. This is especially the case in America. The thieves, after forcing their way into a safe room, next lute up all the crevices 68 MODERN CHEMISTRY AND ITS WONDERS between the door and the walls of the safe by soap or some similar lute. Then they pour the liquid nitro- glycerine in through cracks in the safe door. A detonator is then applied and the explosion usually succeeds in detaching the safe door from the walls, thus making the contents accessible to the criminals. In a recent burglary at the London Hippodrome a gang of thieves, who had secreted themselves in the building after the performance, attacked the night- watchman and after gagging and chloroforming him, proceeded to an underground room known as the treasury and blew open the safe with gelignite. This is the account of the night-watchman: " About 1.30 at night, while patrolling the theatre, I came to the vestibule at the main entrance. I was carrying a bull's eye lantern, and there was a little light coming through the glass doors from the street. Suddenly two men sprang at me and threw me down. One man pinned me down while the other pressed a cloth over my face. There was a strong odour of chloroform, and while I was struggling to free myself I lost consciousness. " It was about 5.30 A.M. when I awoke. My head was aching badly and I felt very drowsy. My lamp was by my side but it had gone out. I at once thought about the safe, and getting up I ran to the door leading to the underground treasury room. It was open. I ran down- stairs and saw the safe, which weighed over a ton, lying on its back. Its door, which had been forced, was all buckled up as if made of tin. All the money (some 500 or so) which was kept in the safe was gone. I at once called in the police." The police soon found that the burglars had turned over the safe, drilled some holes in the cracks of the door, and then forced in a quantity of gelignite (which as put up in cartridges has a creamy consistency). All crevices between the walls and the THE ROMANCE OF EXPLOSIVES 69 door were then sealed up by yellow soap, and the charge was exploded by a time-fuse inserted in the keyhole. The explosion would not make much more noise than the discharge of a rifle, and so was not heard in the street As an agent used for blasting nitro-glycerine is so vastly superior to gunpowder that it must be regarded as one of the most valuable discoveries of our age. Yet it has no value whatever as a projective agent. Exploded in the chamber of a gun it shatters it to pieces. Now what is the cause of the singular difference in the explosive effect of dynamite and gunpowder ? The reason is this : in gunpowder the act of explosion con- sists mainly in the union of carbon and oxygen to produce gaseous products. But the carbon and oxygen atoms are in different molecules. The grains of charcoal and nitrate, although very small, have a sensible magnitude, and con- sist each of many million molecules. Now the chemical union of fhe carbon atoms of the charcoal with the oxygen of the nitrate can only take place on the surface of the grains. The first layer of molecules must be con- sumed before the second can be reached, and so on. Hence the process, although very rapid, must take an appreciable time. In the case of nitro-glycerine and dynamite, however, the carbon and oxygen atoms are in the same molecule at an almost infinitesimal distance apart. Hence the com- bustion takes place in the molecules themselves and is prac- tically instantaneous ; thus : 4C a H 6 (O.N0 1 ) s = 12CO ? +10H 2 0+ 6N 2 + O 2 Nitro-glycerine Carbon dioxide Water Nitrogen Oxygen When the substance explodes the oxygen atoms at- tached to the nitrogen rush for the carbon and hydrogen atoms and unite with them to form carbon dioxide and 70 MODERN CHEMISTRY AND ITS WONDERS steam, while the nitrogen atoms are set free and part of the oxygen as well. The whole molecule is thus suddenly shattered and flies apart into gaseous products which occupy more than 1200 times the volume of the original nitro-glycerine, if the gaseous volume is calculated at ordi- nary temperatures and pressures ; but the heat liberated expands the gas to nearly eight times this volume. And all this takes place almost simultaneously among all the vast assemblance of nitro-glycerine molecules. So that the gas is liberated practically instantly. Now all our experiments are made in air, and this air presses with an enormous weight on every surface. Each square yard of surface supports about nine tons weight. Hence if a volume of gas is suddenly liberated it must press back this weight of air in order to find room for itself. In the case of gunpowder the 300 volumes of gas come off slowly enough to lift and displace the air without getting much compressed. In the case of nitro-glycerine, however, the 1200 volumes of gas come off instantly and cannot lift the air suddenly enough to relieve the pressure. Hence an enormous gaseous pressure is suddenly de- veloped around the explosive, which shatters the material in contact with it. The following illustration may help the reader to realise this more clearly. Take a light wooden surface, say one yard square. Move it slowly through the atmosphere and we encounter little resistance because the air flows round it as it moves. If, however, we force it rapidly forward the resistance greatly increases since the air has no time to flow round it. If we increase the velocity of the motion to that of an express train a mile a minute we would encounter a resistance which no human strength could overcome. Increase this velocity a dozen times, that is to say make it move as rapidly as sound waves, and the air would oppose such a resistance that our wooden board would be shivered into splinters. THE ROMANCE OF EXPLOSIVES 71 Multiply this velocity ten times and not even a boiler plate could withstand the resistance. Multiply the velocity once more by ten and we reach the speed with which the earth rushes round its orbit, about twenty miles a second. To a body moving with such a vast velocity the air at the surface of the earth presents an almost impenetrable barrier against which the strongest rocks may be dashed to pieces. Indeed this effect often occurs when meteorites rush into our atmosphere with planetary velocities. They are often shattered with a loud explosion. Now in the case of a piece of dynamite placed on an open rock or iron plate and caused to explode, we get a volume of gas some thousands of times greater than the volume of the dynamite suddenly shooting forth with a velocity of many miles a second. It encounters in an instant an enormous resistance from the air, and so a sudden gaseous pressure of some thousands of tons is generated all round the dynamite ; and this instantaneous pressure has all the effect of a tremendous blow on the material on which the explosive is placed. Hence it is easy to understand why the strongest rocks and the most impenetrable of iron plates are shivered into splinters by the force of its explosion in the open air alone. In the case of gunpowder the gas is liberated fairly slowly, and consequently such an enormous pressure against the air is never generated. So that gunpowder placed on an open surface in air and exploded exerts no disruptive effect. It is only when its gases are liberated in a confined space that the pressure becomes great enough to shatter massive structures. The reader will doubtless consider that such an enormously swift rush of gas as that which causes a dynamite explosion must be quite exceptional in the scale of nature. Certainly, on the earth gases seldom rush so rapidly. Even in the mightiest storms the wind 72 MODERN CHEMISTRY AND ITS WONDERS seldom travels more than 40 yards a second, whereas the gas rushing from dynamite has a velocity of many miles a second ! but we must remember that anything which is abnormal on the earth may be a normal condition in other parts of the universe. And so it is in this case. In myriads of the suns scattered through space the stupen- dous gaseous velocity which causes a dynamite explosion is vastly exceeded by that of currents of gas in their atmospheres. On the sun, for example, mighty winds of white hot gas rush along with velocities of 700 to 800 miles a second. The pressure and tearing force of such winds must exceed a million-fold the most terrific dyna- mite explosion producible by us. So that over the whole vast surface of the sun there is continually going on age after age, as a normal condition, the same vast explosive action which we see reigning for a fraction of a second when a dynamite bomb explodes 1 The next explosive that we will deal with is gun- cotton. This has a chemical composition somewhat similar to iiitro-glycerine and is produced by the action of nitric acid on cotton. Pure cotton which has been freed from fat and grease by boiling with alkali is immersed in a mixture of concentrated nitric and sulphuric acids (1: 3) for five or six minutes. The cotton is removed and the excess of acids squeezed out. It is next placed in cooled earthenware pots for 24 hours until the process of nitration is completed. The cotton must then be most thoroughly washed in order to remove from it every trace of acid. If this is not done a disastrous explosion may result at a later stage owing to the spontaneous de- composition of the product. In order to carry out the washing, the cotton is first placed in a centrifugal machine, and the greater part of the acid is there wrung out from it. Then it is plunged into a tank containing a large volume of rapidly chang- From Gassier' s Magazine, PLATE 3. Shaping charges of gun-cotton with a band saw. From Gassier s Magazine. PLATE 4. Chiselling and turning blocks of gun-cotton for charging shells. The brass-nose shell is shown on the right-hand stool, and the charge for this on the left-hand stool and in the lathe. THE ROMANCE OF EXPLOSIVES 73 ing water in which the gun-cotton is kept in agitation by a revolving feathered wheel. Afterwards it is boiled with water which usually contains a small quantity of sodium carbonate. The physical character of the cotton fibre is such that it presents every obstacle to the removal of the free acid, since it is built up of capillaries, but by reducing these tubes to the shortest possible length the removal of the acid from their interiors is much facilitated. The material is therefore placed for several hours in a paper-pulper or rag-engine. There it is passed con- tinuously around under the beater knives until it is chopped into a condition of complete division exactly like paper pulp or corn meal. The pulp is then pumped into other vessels and again washed and boiled with water until no trace of acid can be detected by delicate chemical tests in the wash-water. Gun-cotton before pulping and when dry looks exactly like the cotton from which it was made but has a somewhat harsher feel. To prepare the pulp for use in filling torpedoes or shells, the pulp from the rag machine is conveyed to a moulding press and the moulded discs or blocks are taken to a final hydraulic press ; here they are fashioned into the desired form, just as papier mache is. As taken from the press these blocks contain 12 to 16 per cent, of water, but as sent into service they contain about 35 per cent., which is added by allowing the com- pressed blocks to soak in a trough of fresh water until they cease to absorb more. If, in providing charges for torpedoes and shells, it is inconvenient to mould the portions for the heads and other parts, these are readily and without much danger shaped from blocks by cutting them with a chisel or band saw, or boring with a drill, or turning in a lathe, being careful to keep a stream of water flowing on the gun-cotton during the operation. (See Plates 3 and 4.) 74 MODERN CHEMISTRY AND ITS WONDERS Gun-cotton does not readily explode. If a match is applied to it when unconfined it merely flashes away in a whiff of flame. Wet gun-cotton will not burn at all, and bullets may be fired into bales of the stuff without any bad effects. When dry, however, a sharp blow has been known to cause explosion. Consequently it is in the drying houses that explosions of gun-cotton usually occur. Indeed after scores of years of manufacture all danger is not eliminated, and quite a bad explosion occurred so recently as Monday, March 3rd 1913, at Nobel's explosive works in Ayrshire, whereby seven men were killed outright and ten seriously injured. Apparently decomposition occurred among boxes of gun-cotton drying in the heating room, and so violent was the concussion that in a village half a mile away the roofs of houses cracked and came crashing down upon their occupants, while chimney stacks were thrown down in all directions, buildings rocking as if smitten by an earth- quake. At Glasgow, fully thirty miles away, windows rattled in a violent manner and crockery fell down from shelves and was broken. This occurred in a most scien- tifically managed works where every precaution was taken for isolation of the explosive and safety of the workers. In fact this disaster shows that those who have in harness great atomic forces always stand in danger of losing con- trol of them. Like fire, modern explosives are excellent servants but very bad masters. In practice gun-cotton is always set off by means of a detonator charge, which is exploded in the middle of it and thereby gives such a shock to the chemical molecular structure that the whole mass instantly explodes with terrific force, much in the same way that dynamite does. Indeed the tearing effect is much the same in both cases. The chemical constitution of this highly explosive gun-cotton as used in mines, torpedoes and shells is THE ROMANCE OF EXPLOSIVES 75 Js, being produced from cellulose (of which cotton fibre is made up), which has the formula [CgH^OJ^ as the result of the replacement of three hydrogen atoms in the cellulose molecule by three nitro groups, NO 2 , from the nitric acid. " Trinitro-cellulose," as the substance is called chemically, is insoluble in ether but soluble in acetone. There exist, however, lower forms of gun-cotton, in which only one or two nitro groups have entered into the cellulose molecule, and these are soluble in ether, their ethereal solution being known as collodion ; they form the basis of what is known as celluloid. Powders are now made of " gelatinised " gun-cotton, i.e. gun-cotton which by means of partial solution and subsequent evaporation of the solvent is made into a stiff jelly-like elastic mass. One powder of this sort, which has caused much discussion recently, is the French " B Powder." It is a smokeless powder consisting of two parts of insoluble nitro-cellulose (i.e. gun-cotton) mixed with one part of soluble nitro-cellulose (i.e. collodion wool), the whole made into a jelly by adding a mixture of alcohol and ether and stirring until the ingredients form a " jelly," after which the alcohol and ether are eva- porated. Such powders formed of " gelatinised " nitro-cellulose or gun-cotton are for some unknown reason much more unstable than the ungelatinised parent substances, al- though apparently the process of gelatinisation is a merely physical one attended by no chemical change. When kept for some years such powders often gradually decompose with increasing rise of temperature, and then suddenly the decomposition becomes so marked and the rise of temperature so great that the mass may explode with great violence. Consequently the French naval authorities have decreed that all B Powder over four years old shall be destroyed by being sunk in the sea. 76 MODERN CHEMISTRY AND ITS WONDERS This discovery was only made at the cost of human life, owing to a terrible series of disasters to French battle- ships. First of all the French battleship Jena blew up with a terrible loss of life, to be followed very shortly by a still more appalling disaster. On Monday, September 23rd 1911, at 5.35 in the morning an unexpected explosion took place on the battleship Liberte lying at anchor in Toulon harbour. As the alarmed men swarmed up from below, this explosion was followed by a series of others of fearful violence, culminating in a terrific explosion at 5.55 A.M., which could be heard thirty miles away. The air around was filled with debris, a captain on a training ship two miles away being killed by a flying fragment, while great chunks of massive iron armour, weighing tons, were hurled in all directions around the ill-fated vessel, crashing through the sides and decks of neighbouring warships and killing and wounding men in all directions. In a few minutes no less than 200 lives were lost and the noble vessel was reduced to a mass of twisted and torn scrap metal. Our illustration shows the battleship Liberte after the explosion (Plate 5). Cordite is a mixture of nitro-glycerme, gun-cotton, and vaseline in the proportions : nitro-glycerine, 30 parts, gun- cotton, 65 parts, and vaseline, 5 parts. The combustion of the powder without vaseline causes excessive friction of the projectile in the gun, producing rapid wearing of the rifling ; it is chiefly to overcome this that the vaseline is introduced, for on explosion a thin film of greasy matter is deposited in the gun, and acts as a lubricant. In order to prepare this substance the nitro-glycerine is poured over the gun-cotton and well mixed by hand ; then acetone is added and the whole mingled in a knead- ing machine for 3J hours. The acetone does not enter into the constitution of the powder, but since it dis- THE ROMANCE OF EXPLOSIVES 77 solves both the nitro-glycerine and the gun-cotton it allows them to be thoroughly mixed and incorporated into a homogeneous mass. The acetone is afterwards removed during the drying process. Vaseline is now added and the kneading is continued for some hours. The cordite paste is first subjected to a preliminary pressing, and is finally forced through a hole of the proper size in a plate by hydraulic pressure or by hand. The thick fibrous paste, if of a small diameter, is wound on drums, whilst if of a large diameter, it is cut off in suitable lengths. The most tedious process is the drying out of the solvent acetone. If the drying is done quickly, the surface of the cords is hardened, and the solvent cannot escape from the interior. Large cordite may thus require as many as seventy days in which to dry com- pletely. This drying is effected in steam-heated stoves, and the drying of the exterior surface must proceed only as quickly as the interior will give up its solvent to the more outward portions. It is for this reason, among others, that a large store of cordite is necessary to meet possible demands, because the substance cannot be made in a day or a week, and any hurry in drying would cause the rods to split and alter their rate of burning and so spoil their ballistic properties. Cordite is a splendid ammunition for guns, and forms the basis of what is now known as smoke- less powder. It is perfectly safe, a rifle bullet fired into a mass of it only causing it to burn quietly, while a detonator cannot be made to explode it. Balliste consists of nitro- glycerine 37*5 per cent, and nitro-cotton 62*5 per cent. -I It is impossible in the course of an article such as the present to pass in review all the numerous ex- plosives that are known. 1 We should however mention Picric Acid, C 6 H 2 (NO 2 ) 3 OH, which is prepared by dis- 1 For further details the reader should consult the author's book, Industrial Chemistry, vol. i., " Organic," where a full account of the subject is given. 78 MODERN CHEMISTRY AND ITS WONDERS solving phenol, C g H 5 OH (carbolic acid), in nitric acid. It or its salts are used for shells under the names " Lyddite," " Mellinite," &c. Trinitrotoluene, C g H 2 (NO 2 ) 3 CH 3 , is now very largely used and is stated to be superseding picric acid. Picric acid assumes the form of a crystalline solid, composed of a mass of very beautiful bright yellow plates or prisms. In fact it was (and still is to some extent) used as a yellow dye. Picric acid under ordinary circumstances is quite safe to make. In fact, students in chemical laboratories are allowed to make the substance as an exercise ; it can be melted without danger, and even be allowed to burn without explosion. Although so safe under ordinary circumstances, yet when exploded with a mercury ful- minate detonator it goes off with fearful violence, being even more powerful than gun-cotton or dynamite. When picric acid explodes it belches forth extremely poisonous gases. Among these we may mention the suffocating carbon dioxide and nitrogen, the blood- poisoning carbon monoxide and nitrogen oxides, the latter of which when breathed causes pneumonia and a suffocating death, while the former is the active agent of gas poisoning in mine explosions ; last but not least there are evolved vapours of the deadliest of all poisons namely, prussic or hydrocyanic acid (p. 48) a single breath of which can kill a man with the suddenness of the knife. In addition to this, the intense heat of an exploding shell converts part of the picric acid charge into very bitter and irritating vapours, which dye all objects in the immediate neighbourhood a deep yellow colour. We can, therefore, readily imagine the really terrible effects produced by the explosion of great shells weighing nearly a ton, especially if the explosion takes place in a THE ROMANCE OF EXPLOSIVES 79 somewhat confined space, such as the hold of a battleship. First there is the terrific thunder and blaze of light of the explosion itself ; then comes a sudden increase of air pressure, and the men not annihilated by the explosion itself are hurled in all directions ; lastly come torrents of intensely poisonous gases evolved as a result of the decomposition of the picric acid. Men gasp and die suddenly, killed by the prussic acid and nitrogenous fumes. Such men will appear black and livid in the face, and are often stained yellow by vapours from unexploded picric acid. In fact by the aid of the enormous guns constructed by modern science the very strongest land fortifications can be reduced to ruin in a few hours. We are told, for example, that some of the Antwerp forts were literally blown into the air by shell fire, so that what was once a fort was transformed into a deep cavity. The great 15-inch shells of the English Navy hit with precision at 12 miles and pound to dust everything within a hundred yards, while ranks of men are hurled down by such shells when more than a quarter of a mile from the place whereon the projectile falls. Byron's words, written over a hundred years ago : " The armaments that thunderstrike the walls Of rock-built cities, making nations quake And Monarchs tremble in their capitals." seem almost literally descriptive of the overwhelming nature of modern shell fire when directed on fixed land forts. Picric acid for military purposes is usually fused and poured while in a molten condition into the shell. The disadvantage of its use, however, is that it is an acid, and so combines with metals to form salts called " picrates," some of which are very explosive and unstable bodies. 8o MODERN CHEMISTRY AND ITS WONDERS There is, therefore, always the danger that the metal forming the shell and the picric acid charge inside may unite to form some of these unstable explosives, and so cause a disastrous premature explosion. For these reasons another nitro-derivative, viz., Trinitrotoluene , C 6 H 2 (NO 2 ) 3 CH 3 , has recently come into extended use, although it is not quite such a powerful explosive as picric acid. It is made by treating toluene (which is contained in coal tar) with nitric and sulphuric acid. It crystallises in yellow masses, and is really an extraordinarily safe explosive. For example, it can be burnt, hit with a hammer, bullets can be fired through it, and all sorts of other rough mechanical treatment meted out to it without causing it to explode. As much as one ton weight of the substance has been known to burn away quietly without explosion. Moreover, it has no acid properties, and so it will not (like picric acid) combine with metals to form unstable explosive compounds. By means of a detonator of mercury fulminate it can be caused to explode with very great violence although not so violently as wet gun- cotton. The fragments of shells filled with this substance are large enough to do much damage at a considerable distance, whereas picric acid and gun-cotton tend to pulverise shells and so localise their effect. One curious effect of the outbreak of war, therefore, is to make supplies of a number of products derived from coal tar of great military importance. Thus coal tar contains both phenol and toluene, from which are made picric acid and trinitrotoluene respectively. Even benzene becomes valuable from the military standpoint, because from benzene we can make phenol and so make picric acid. The very first thing, therefore, that a Government does on the outbreak of war, is to commandeer huge THE ROMANCE OF EXPLOSIVES 81 supplies of benzene, toluene, phenol and similar coal tar products. Great care, too, is taken to prevent the export of such chemicals to foreign countries, where they could be used for making ammunition for sale to the enemy. Mercury fulminate, C 2 N 2 O 2 Hg 2 , is a most dangerous and sensitive explosive much used for making percussion caps, detonating fuses, and the like. It may be prepared by dissolving mercury in nitric acid and then adding alcohol to the solution. A violent action soon begins, dense clouds of white and then orange coloured vapours are evolved, and the mercury fulminate is precipitated in small, gray, beautifully formed crystals, which are washed with water and stored wet in guttapercha vessels. A slight blow will cause it to explode with a loud detonation, and the easy method of preparation has caused it to be much used by anarchists in their 'bombs. Last of all we will mention a curious explosive called Nitrogen Chloride. In the year 1811 it occurred to a famous French savant called Dulong, to pass chlorine gas into a strong solution of ammonium chloride (sal am- moniac). To his surprise he noticed that a peculiar yellow oil began to collect at the bottom of the vessel. He collected a small amount of it and began to examine its properties more closely, when all of a sudden it ex- ploded with terrific force, blowing out the unfortunate man's eye and shattering into a pulp three of his ringers. This compound is now known to be nitrogen chloride, and is, perhaps, the most dangerous explosive known. Its formation may be represented thus : NH 4 C1 + 3C1 2 = NC1 3 + 4HC1 Ammonium chloride Chlorine Nitrogen chloride Hydrochloric acid Wishing to preserve others from a like accident, Dulong kept his knowledge to himself and so it came about that a similar accident happened in 1813 to Fara- F 82 MODERN CHEMISTRY AND ITS WONDERS day and Davy. Faraday was holding a small tube con- taining a few grains of this yellow fluid between his finger and thumb, when he was stunned by a bright flash followed by a violent thunderlike explosion. On returning to consciousness he found himself standing with his hand in the same position, but torn by the shattered tube, and the glass of a thick mask he was wearing cut by the projected fragments. The substance is, in fact, terribly explosive. The slightest touch of an oiled feather, a beam of sunlight falling upon it, or some slight vibration like that caused by a door slamming in the distance, may cause it to explode. Nitrogen chloride is composed of two elements, both of which are gaseous at ordinary temperatures, and they are held together in the liquid form by very weak chemical forces. The explosion is simply the sudden resolution of the oily liquid into its component gases, nitrogen and chlorine, thus : 2NC1 3 = N 2 + 3C1 2 Nitrogen chloride Nitrogen Chlorine A substance like this, however, is far too dangerous to be of any practical use as an explosive. After all the various accidents and disasters which have been related in the preceding pages, the reader will be rather surprised to hear that commercial explosives are comparatively safe substances when properly handled. So safe are they, in fact, that this often actually leads to disaster by the indifference with which workmen handle them. There are cases on record where work- men have melted frozen nitro-glycerine in a frying pan over an ordinary fire ! While in mining districts the miners will often carry about in their pockets dynamite cartridges, which if exploded would blow them to pieces. Indeed only a short time ago a rather curious case THE ROMANCE OF EXPLOSIVES 83 happened near Nottingham. It chanced that two miners, accompanied by a friend, were taking a walk on a Sunday afternoon on a waste bit of ground in the neighbour- hood. They wished to show this friend the effect of an explosion, and so one of them pulled out a cartridge from his waistcoat pocket, applied a light to the fuse, and threw the cartridge to a safe distance. Now every miner has a dog, who takes an intelligent interest in all that his master does. No sooner did the little animal see an object whirling through the air than he immediately thought that this was something thrown for his especial benefit, and that he was required to fetch it, and raced in pursuit. He caught the cartridge in his mouth and then came running back towards the men. These, horror-stricken, fled wildly, with the dog pursuing them. Although the miners developed a record speed, the dog soon caught them up. Luckily the dog had, by seizing the fuse, put it out, and so the situation was saved. And now I should like to say a few words about a subject on which a great deal of misapprehension exists. If in the case of modern high explosives we have com- mand of powers so vast that mountains can be rent asunder and steel twisted and shattered as if made of paper, why cannot we apply these same powers for driv- ing engines ? Would not these same powers placed in the cylinders of engines of suitable construction drive them with far greater power than the ordinary propellant- agent powers, such as gas, steam, oil and electricity ? The answer is that there is far more work to be obtained out of, say, 1 Ib. of coal or petroleum, than out of the same weight of dynamite, and that explosives are only valuable technically because they liberate their energy in a very short time. For instance 1 kilogram of liquid petroleum when burnt develops the amount of heat represented by 12,000 84 MODERN CHEMISTRY AND ITS WONDERS calories, and average coal about 8000 calories, whereas 1 kilogram of dynamite (with 25 per cent, kieselguhr) will only develop 1300 calories. So that the amount of energy liberated by burning 1 kilogram of petroleum or coal would cause an engine to do eight or nine times the amount of work that could be obtained by causing the engine to be set into motion by the power liberated by decomposing the same weight of dynamite. Also the actual utilisation of the energy liberated by explosives compares very unfavourably with that of a high-class engine of the Diesel type, where the efficiency may rise to 37 per cent, of the theoretical, whereas in an engine driven by explosives the efficiency is only 15 to 20 per cent, of the theoretically possible. Consequently the employment of high explosives as motive agents has little prospect of success. All explosives are substances in a state of strain, from which they release themselves when they explode. They may be compared to compressed springs which contain energy stored up in them which they give out when they perform mechanical work. All explosives, therefore, contain energy stored up in them, and 'this energy mani- fests itself when they decompose in the production of heat and the increase of volume which is so characteristic a concomitant of explosions. Explosive compounds must have this energy put into them at the moment of their formation. In other words, they must be formed from their elements with the absorption of heat. It is the heat which thus disappears in them when they are formed which reappears again when they explode, and which gives them their awful power. And experiment confirms theory. It is found that the heats of formation of explosive compounds are negative. In other words, they are formed from their elements with the absorption of heat. Now it is quite incorrect to assume that very high THE ROMANCE OF EXPLOSIVES 85 temperatures decompose all chemical compounds into their elements. The science of thermo-dynamics teaches us that with rising temperature those compounds tend to be formed whose production is attended with the absorp- tion of heat. Thus, in the electric arc at 3000 C. oxygen and nitrogen unite together, heat being ab- sorbed in the process. Further, the well-known com- pounds benzene and acetylene are formed from their elements, carbon and hydrogen, at the very highest temperatures, with the absorption of heat. Moissan has shown that at the enormous temperature of the electric arc carbon unites directly with many elements to form compounds called " carbides." A large number of these are formed from their elements with the absorp- tion of heat and will explode when struck at ordinary temperatures, then evolving the heat they had absorbed in their formation at high temperatures. In general the higher the temperature at which a reaction takes place the greater is the quantity of heat that is absorbed by it. A similar law prevails for the influence of pressure. An increase of pressure favours the formation of products which have small volumes. In other words, a very high temperature combined with a very high pressure will tend to produce compounds containing a very large amount of heat stored up in them, and possessing a very small volume. Such compounds, therefore, should exhibit explosive properties. For when they decompose they liberate all the large quantities of heat stored up in them, and at the same time they will form products of a greater volume than themselves and thus generate a sudden pressure. Arrhenius * has been led by these considerations to put forward some interesting theories to account for the stupendous explosions which take place on the sun, and, 1 Das Werden der Welten, pp. 82-84. 1908, 86 MODERN CHEMISTRY AND ITS WONDERS doubtless, on all the visible stars. He believes them to be due to the action of explosive compounds which are produced in the interior of the sun under the enormous temperatures and pressures there prevailing. When these compounds are brought up near the surface again by the violent movement going on all over and inside the giant mass, they explode with enormous power, shooting aloft a column of molten and gaseous debris thousands of miles long and billions of tons in weight. A dynamite explosion can scarcely ever hurl a projectile more than a few thousand feet a second, but these celestial explosives hurl millions of tons of matter aloft at the rate of hundreds of miles a second. They have an energy millions of times greater than any explosive ever made by man. Arrhenius pictures the gases of the upper levels of the sun's atmosphere rushing downwards into the mighty depths of his body, just as we see them doing in sunspots. As they plunge downwards towards the interior the pressure keeps on increasing enormously, the increase being about 3500 atmospheres per kilometre descended. At the same time the temperature rapidly rises, flaring up to the giant heat of many millions of degrees centi- grade. Under these conditions they unite to form com- pounds. Yes, the very gases which, in consequence of the high temperatures and low pressures prevailing in the outermost levels of the sun (outside the clouds of the photosphere), fall apart into atoms, enter into chemical combination in the depths of the sunspots. But what strange compounds are these ! They are utterly unlike any that we know upon the earth. They require enormous quantities of heat for their formation, quantities which transcend those required for the formation of earthly chemical compounds in the same degree that the temperatures in the sun transcend those at which THE ROMANCE OF EXPLOSIVES 87 chemical processes proceed upon the earth. We must therefore picture to ourselves that deep in the interior of the sun there exist compounds which when brought to the surface suddenly flash with an appalling roar into their elementary atoms again, liberating as they do so the enormous quantities of stored up heat, and vastly increasing in volume. Such compounds must be regarded as the mightiest of all explosives, in comparison to which all earthly explosives are mere playthings. We indeed can form no conception of their titanic energy. We see their effects when billions of tons of gases come bursting through the photospheric clouds which surround the sun and go rushing upwards for hundreds of thousands of miles, often with velocities that are to be measured in hundreds of miles a second. These velocities exceed a thousand-fold those of our swiftest gun projectiles, and consequently the explosives in the interior of the sun must be over a million times more powerful than earthly explosives, for the energy increases with the square of the velocity produced. That there can really exist sub- stances so rich in energy is shown by the case of radium. This, as shown by Rutherford, will liberate before decom- posing a thousand million calories per gram mass a quantity of heat which exceeds that produced by the burning of an equal weight of coal nearly 250,000 times. These ideas of Arrhenius are interesting because they give us a glimpse into a hitherto undreamt of region of chemistry, which only comes into existence under the stupendous temperatures and pressures prevailing in the stars, and which we can never hope to attain in our earthly laboratories. CHAPTER IV RADIUM AND THE NEW CHEMISTRY NEARLY three hundred years ago there appeared a vision to the immortal William Shakespeare when at the summit of his mental activity, and he wrote it down as follows in the phraseology of his age : " And like the baseless fabric of a vision The cloud-capped towers, the gorgeous palaces, The solemn temples, the great globe itself, Yea, all which it inherit, shall dissolve, And, like this insubstantial pageant faded, Leave not a rack behind." It was not, however, until quite recently that men dis- covered that this picture of a world fading away is pro- bably a literally true one of what is actually taking place in Nature to-day. Modern discovery has made it ex- tremely probable that the elements are not eternal, as we once thought, but are themselves in change, withering away with age like all other things. Even the very atoms, those foundation stones of the universe, are now thought to be born, grow old, and die. This immense revolution in human thought all arose from a chance observation of the great French physicist, Becquerel, in 1896. It appears that he was examining compounds of a heavy element called Uranium, when he made the startling discovery that even in the dark it affected a photographic plate like sunlight. 1 At the same 1 Niepce de Saint-Victor appears to have been the first who discovered this fact many years ago. Le Bon claims to have anticipated Becquerel in some of his work. 83 RADIUM AND THE NEW CHEMISTRY 89 time the air all around the uranium compounds was found to have acquired the power of conducting electricity and soon discharged the most carefully insulated electro- scope. A great impetus was given to these researches when a lady, Madame Curie, traced many of these results to the presence of a mysterious new element which she called " Radium." The ray-emitting power of this new element was perfectly astonishing ; it possessed nearly two million times the activity of an equal quantity of uranium. What distinguished this element from any other one previously known was that it was continually shooting out into space with incredible velocities tiny electrified particles which, falling upon a photographic plate, produced the effect of sunlight. The flying particles, moreover, rendered all the air around electrically conductive and so caused the discharge of any electrified body in the neighbourhood. The wonder increased when it became known that, weight for weight, radium was by far the most dangerously poison- ous of all the known elements. It even poisons at a distance, in that the tiny electrified particles shot off from it become embedded in the flesh of animals and cause virulent sores and ulcers which take months to heal. Indeed I suppose that if ever it is found possible to collect a ton of the element together into one place it will be found to be certain and agonising death to approach to within a yard or two of it, even if actual contact with the element is avoided altogether. In addition to being the most poisonous element known, radium also enjoys the distinction of being the most expensive substance at present purchasable upon the earth's surface. In 1913, for example, the market value of radium was about 16,000 a gramme, or in Eng- lish measures, 450,000 an ounce, 7,200,000 a pound 1 This enormous costliness has, and is now, driving 90 MODERN CHEMISTRY AND ITS WONDERS mineral prospectors all over the world into the most unlikely and wild regions in the hope of alighting on some great sources of radium, hitherto undetected on account of the inaccessibility of the country. Weird have been the stories told of dangers and escapes of these bold pioneers of civilisation. Indeed some have even perished miserably in their search, one of the saddest cases being that of Mr. J. H. Warner, who, in 1913, with two natives penetrated into unexplored parts of Papua (New Guinea). He was killed and eaten by the ferocious natives of that part, his two companions escaping. But another and more astonishing fact was soon dis- covered. It was this : unlike anything else previously known, and apparently in contradistinction to all known laws and theories, radium was found to be hourly emitting very large quantities of heat, without itself undergoing any noticeable amount of change, either physically or chemically. And this heat evolution continued, without noticeable signs of diminution, hour after hour, day after day, century after century, for thousands of years. Curie and Laborde found that in a single hour a piece of radium emitted enough heat to raise an equal weight of water from its freezing point to its boiling point. One ton of radium enclosed in a suitable boiler would cause one ton of water to boil within one hour, and would keep it boiling continually for more than a thousand years. The energy given off by 12 pounds of radium, if fully utilised under the boiler of a perfect steam engine, would develop one horse-power continuously. The reader can easily calculate from this that 32 tons of radium in the furnaces of a great liner like the Maure- tania would propel the ship by developing the same power as is now generated by the daily combustion of some hundreds of tons of coal under her boilers. However, RADIUM AND THE NEW CHEMISTRY 91 32 tons of radium would, in the first place, be unattain- able ; and in the second place, even if obtainable, this amount of radium would cost at present prices some 500,000,000,000. The annual interest on this vast capital expenditure would be at least 20,000,000,000, a sum which in itself would more than pay for all the coal consumed by all the ships in the world, for I do not know how many thousands of years to come. The prospects, therefore, of employing radium for driving steamships do not look particularly rosy. Moreover, even supposing the discovery of some vast deposits of radium in the future in some wild country should solve the problem of supplying tons of radium at a moderate cost, nevertheless, our difficulties would not be overcome. For, as al- ready mentioned, radium is by far the most poisonous substance known, emitting vapours and effluvia which are perfectly deadly ; consequently the isolation of the radium in such masses so as to render the escape of all deadly rays and effluvia impossible, would be a decidedly difficult engineering feat. However this may be, I think that it will be quite clear to the reader that this new element is spontaneously emitting simply enormous amounts of energy. Conse- quently men quickly realised that they were in the presence of an altogether new order of phenomena, unlike anything that had ever been perceived upon the earth before. And soon the most advanced thinkers were at work, explaining these remarkable properties of the new element. The present writer was, I believe, the first to suggest the correct explanation, namely, that the radio-active elements are decomposing elements. 1 1 My attention has been called to the following passage, which occurs in the preface of Mr. Soddy's interesting book, entitled The Interpretation of Radium (1909) : " The present day interpretation of radium, that it is an element under- 92 MODERN CHEMISTRY AND ITS WONDERS This conclusion was later confirmed by Rutherford and Soddy, who actually isolated the elementary products of the decomposition of the elements. And so it was going spontaneous disintegration, was put forward in a series of joint scientific communications to the Philosophical Magazine of 1902 and 1903 by Prof* Rutherford . . . and myself." I should like to point out here that Messrs. Rutherford and Soddy were not the first to suggest that the radio-active elements are dissociating elements. So far as I am aware, the first definite statement to that effect occurs in the Chemical News of May 2, 1902, in a paper by myself entitled The Radio-active Elements considered as Examples of Elements undergoing Decomposition at Ordinary Temperatures, together with a Discussion of their Relationship to other Elements. In my paper the following very definite statement occurs : " For many years there has been a general disposition to revive the ancient notion that all matter is composed of a common ' protyle,' and that the elements have been formed from it by a successive series of condensations. And undoubtedly powerful experimental evidence has been furnished by the spectroscopic researches of Sir Norman Lockyer, who believes that the terrestrial elements are more or less completely dissociated into substances of a simple constitution at the high temperatures pre- vailing in the sun and stars. But what has hitherto been wanting is some ex- perimental evidence that the elements do actually dissociate at temperatures attainable in the laboratory. But it appears that we now have this evidence, for the radio-active elements appear to be actually decomposing at ordinary tempera- tures." It is also definitely stated that " radio-activity " is a general property of matter a conclusion now generally accepted. The paper attracted attention in America, and Prof. Baskerville, in his Presidential Address to the Chemical Section of the American Association (see Naturc t ~Ft\>. 25, 1904, p. 403), did me the honour of referring to my paper as follows: " Many have theorised as to the ultimate composition of matter. The logic of Larmor's theory (Phil. Mag,, December, 1897, p. 506), involving the idea of an ionic substratum of matter, the support of J. J. Thomson's experiments (Phil. Mag., October, 1897, p. 312), the confirmation of Zeemann's phenomenon, the emanations of Rutherford, Martin's explanations (Chemical News, 1902, Ixxxv., 205), cannot fail to cause credence in the correctness of Crookes's idea of a fourth state of matter." Messrs. Ruther- ford and Soddy, therefore, cannot be credited with being the first to put forward the theory that the radio-active elements are slowly decomposing. What they have done is to confirm by their brilliant experimental work my main thesis as regards the nature of the radio-active elements. Their first paper, " The Radio- activity of Thorium Compounds" (fourn. Chem. Soc., 1902, Ixxxi., 321), con- tains no statement of this theory. Their second paper (loc. cit. t p. 837) contains on p. 859 a statement of the theory in cautious language ; this paper, however, was only published in June, 1902, after the appearance of my paper. Messrs. Rutherford and Soddy's first communication to the Philosophical Magazine " On the Cause and Nature of Radio-activity" was published only in September, 1902, RADIUM AND THE NEW CHEMISTRY 93 that the dreams of a whole generation of the most advanced thinkers, of Faraday, Brodie, Crookes, Herbert Spencer, and Lockyer, were realised at last, and it was proved that men had in radium nothing more nor less than a decomposing element ! The radium atom was conceived of as consisting of an enormous number a quarter of a million of electrons whirling round with the speed of over a hundred thousand miles a second. As they whirled, the atom was supposed to radiate away energy, and finally to burst like a bubble, shooting out into space with enormous speeds the tiny particles which compose it. It was these tiny flying electrons that were supposed to give rise to the rays which affected a photo- graphic plate. Careful examination showed, however, that these rays were of no simple nature. At least three different sorts were evolved, which are now known respec- tively as the a, ($, and y rays. Besides these it was found that a peculiar radio-active gas, called an emanation, was given off which obeyed Boyle's law, but was chemi- cally quite inert and much resembled the inert gases of the atmosphere, namely, Helium, Argon, Krypton, Xenon, and Neon. Sir William Ramsay and Soddy have con- sidered it to be an unstable element of atomic weight over 200, which breaks down rapidly, throwing out rays as it does so, and after a month it has lost practically all its radio-activity. Among the products of change are Rutherford's A, B and C varieties of radium and gaseous helium. The a-rays are small particles shot out from the radium atom with velocities ranging up to 12,000 miles a second. They are charged with positive electricity, and when they strike a screen made of zinc blende the molecular impacts cause a sea of scintillating points to occur. It has been supposed that these particles are helium atoms, for their mass has been shown closely to 94 MODERN CHEMISTRY AND ITS WONDERS correspond to those of helium atoms, and helium is known to be a product of the decomposition of the radium emanation. The /3-rays are tiny particles possessing a mass of scarce the thousandth part of that of a hydrogen atom. They are negatively charged and fly off from the radium atoms with tremendous velocities. Some of the particles possess an initial velocity of over 160,000 miles a second ! The *y-rays are extremely penetrating, passing through a screen of aluminium 8 centimetres thick before their intensity is halved. They travel with a velocity greater than that of the /5-rays, but their true nature has not as yet been ascertained. The existence of these terrific motions inside an atom teaches us that within the atoms of matter there is a fund of energy so incalculably vast that it is altogether difficult to obtain any clear idea of it. It has been calculated that a single ounce of radium, were its internal motions fully available as motive power, would lift ten thousand tons a mile from the earth. Hydrogen and all other elements probably contain equal stupendous reservoirs of power, and it seems certain that all the energies previously known to us, which manifest themselves in the heat and light and electrical excitement of chemical combination, are merely overflow tricklings from the immeasurable ocean of intra-atomic energy. And now a solemn thought arises : Astronomy has long taught us that we inhabit but a dead ember swimming wide in the void of space, a grain of dust flung at random into a fathomless abyss ; we are lighted up from 90 millions of miles away by a more horrible hell-fire than ever the morbid mind of mediaeval priest conceived ; afar off and all around us other dead embers, other flaming suns, wheel and rush through the apparent void often at the rate of a million miles a day ; the RADIUM AND THE NEW CHEMISTRY 95 nearest sun is far beyond our reach, the farthest so remote that the mind fails in its endeavour to conceive of the distance. And so, alone in space, the world rushes forward far swifter than any rifle bullet into the unknown, spinning dizzily as it flies, surrounded on all sides by gigantic fires and terrific forces. Surely, if we come to consider it, the world is a strange, if not appalling place of residence. Shipwrecked mariners, though they cling but to a wave-swept boom, would seem safe com- pared to mankind on its bullet. And yet, so uncon- scious are we of the motion, to us our planet appears as a green, commodious home ; and the gigantic flames which rear aloft from the sun do but ripen fruit and flower, and warm mildly our smiling summer landscapes ; and we unconcernedly go to work, think our little thoughts, do our petty deeds, while all around us in the darkness the universe wheels and roars like a gigantic machine. Yes, safe, very safe, appears our little earth to us. But now radium has revealed a new and startling possibility. Are we not bestriding an explosive a million times more powerful than any explosive ever made by man ? If atoms can explode as radium atoms explode and fly to pieces with a speed of a hundred thousand miles a second as radium atoms do could not some sudden shock let loose this terrific energy residing in all matter atoms, much as a detonator explodes dynamite or gun-cotton, and so cause the whole world to disappear in one enormous flash of light ? Such things could conceiv- ably happen, and the glare of the catastrophe would be heralded to the distant worlds of space but by a new star shining briefly in their skies. New stars appear and disappear, and some writers have supposed that matter can thus, under suitable con- ditions, explode into a mist of flashing ultra-atomic particles. Truly, the recent advances which science has 96 MODERN CHEMISTRY AND ITS WONDERS made have revealed to us possibilities undreamt of by our forefathers, or even by the scientists of a few decades ago. A most interesting observation has been made by Prof. Bragg. He has shown that the alpha particles shot off from the radio-active elements go clean through matter atoms, knocking off electrical particles in their passage and so making the air around a conductor of electricity. He proved this by sending a stream of these alpha particles through a thin metal screen, which robbed each particle of some of its energy, but did not bring a single one to rest. The number of particles in the stream remained unchanged until their velocity had diminished to some 5000 miles per second, after which their subsequent history could not be traced. Now as each particle must have plunged right through some hundreds of thousands of atoms before emerging, we have in this the proof that the alpha particles have passed in their wild flight clean through the metal atoms, much as a rifle bullet will pass clean through a man. The vista opened up by this fact will be brought home to the reader when I tell him that now for the first time since science began we have been able to pass anything through an atom. When two molecules of a gas collide they approach within a fairly definite distance, and the approach is followed by a recession under new conditions of motion. Each molecule, however, has a domain into which no other molecule can penetrate which is roughly the volume swept out by the radius of the molecule. But the defences which guard the molecular domain break down before the onslaught of particles flashing forward at the rate of 12,000 miles per second, and so the alph particles crash right through the atoms, and their collisio- are rather with one or other of a number of circumscrir and powerful centres of force which exist quite inside atoms and act with great power when approached wi RADIUM AND THE NEW CHEMISTRY 97 distances small in comparison with the atomic radius. Hence we can pass right through the atom an alpha particle, which is simply an atom of helium, and then see what has happened to it when it has come out again, and from the treatment which it seems to have re- ceived we can try to understand what it has met with inside. Not only can this be done with the alpha rays, but also with the beta particles (which are electrons) and the gamma rays (X-rays), and so we have at once a powerful instrument for leading us into the mystery of atomic structure itself. And thus it is that we have presented to us possibilities of obtaining a glimpse of a world beyond the atom, and of discovering the arrangement of the interior of the atom. The chemical examination of radium showed that it was an element belonging to the calcium, strontium and barium group of elements, but of a greater atomic weight than either of these. Very careful determinations of this constant by M. and Mme. Curie gave it an atomic weight of 226-2 (O = 16). The heat evolved from radium was also found to be a secondary effect, the particles shot out by the exploding atom causing molecular shocks to the neighbouring molecules, thus generating a molecular movement in the neighbourhood which registers itself as heat. Curie and Laborde found that the temperature of a specimen of pure radium bromide remained constantly 3 C. higher than that of the surrounding air. A really wonderful feat which has recently been per- rmed is the actual counting of the number of alpha 'Vticles hurled forth per second by the decomposing )( io-active elements. When it is recollected that each : iese particles rushes forth from the radium atom at Prodigious speed of about 12,000 miles per second, G 98 MODERN CHEMISTRY AND ITS WONDERS and that from one gram of radium 136,000,000,000 of these helium atoms are expelled per second, the reader will realise what a remarkable feat this actual counting is. And yet it was done in the simplest possible manner by two distinct methods. First of all is a method de- pending upon the fact that when an alpha particle (that is to say an atom of helium) is expelled from an atom of radium and crashes against a sheet of zinc blende, at the point where the helium atom strikes the blende a tiny blaze of light appears. So that if we bring an ex- tremely small amount of radium near such a sheet of zinc blende in the dark and examine the surface of the mineral by means of a lens, we see flashes of light coming and going, appearing like stars in the sky ; and by count- ing the number of stars which thus appear per second and knowing the quantity of radium producing this effect, it is possible to find out the number of atoms of helium thus expelled from the radium per second. The other method depends upon the fact that each atom of helium as it flies through the air after being shot off by the atom of radium renders the air in its path conducting. Now matters are so arranged that the particle in its flight is allowed to pass between two highly charged metallic surfaces, which are insulated from each other by rarefied air, and are connected to a galvanometer. As the particle flies between them the air becomes conducting and an electrical discharge takes place from one to the other, causing the galvanometer to give a little movement. When the next particle comes flying along there is another movement of the galvanometer, and by simply counting the number of kicks the galvanometer makes in a minute we can count the number of alpha particles flying off from the radium. Some people have doubted the existence of atoms, but here we have, for the first time in history, the direct RADIUM AND THE NEW CHEMISTRY 99 effect of single individual atoms ; so that, indirectly, the URANIUM/ \__.a 3X,0YR5.Vy^. a? -o* lO'OYRS.l)^ *"N k UR.X { \ 1 MESO. f\ ZZ OAYsl A. /-S V V A V TVl" ACTIN.UM/ \ i\' ,ON,UM (^\ S^ ^' |^\ ? V A'a x--x ,^I".^A >> RADI-O ACT /" N 1 9 5 DAY: RADIUM / \ 1760 YRS.l /-*. a TM. x. 57 DAYS ^-p ACT. A. ^ -v^ IODAYS EMANATION^ \ 3-75 DAYS V h~*' ? T " ? RAI 4O YRS.(