RADIUM AND THE X-RAY
Professor Röntgen’s Discovery—The Triumph of the Curies— How the X-Ray detects Fraud—Its Value in Science.
RATHER more than thirty years ago there came to Paris a young Polish girl named Marie Sklodowska. Her father had been a man of science, and she had been brought up in his laboratory, but a revolutionary plot had broken up her home and forced her to take refuge in France. She was very ambitious to complete her scientific training, and, to do so, obtained work in a laboratory, where she washed bottles for a bare living, feeding on bread and milk, all the time working long hours of the night at her studies in order to pass her examination for a degree in science. At the University she met a young French student named Pierre Curie. They fell in love, and in 1895 were married. Together they worked hard and steadily, and in 1898 Madame Curie received her degree, and she and her husband turned to original research.
The particular study which interested the young couple was that of the rays given off by vacuum tubes. Twenty years earlier, in 1879, the English scientist Sir William Crookes had discovered that the negative pole of a vacuum tube, when excited by high-tension electricity, gives off rays of a very peculiar order. He named them cathode rays, and they were afterward shown to consist of particles of negative electricity known as electrons.
Other men of science experimented with these rays, but it was not until 1895 that Professor Röntgen announced that he had obtained from a vacuum tube a new light which was able to penetrate many substances hitherto regarded as opaque. The heaviest black paper was no bar to the passage of these rays, and they were able to affect a photographic plate. No scientific discovery ever made a greater appeal to popular imagination, and few have had greater results. The new rays opened up a whole new field to the surgeon and the doctor, who now, for the first time, could see a broken bone without first cutting through the flesh, or could watch the movement of food in its various stages in process of digestion. A hundred other uses soon appeared, of which I have more to say a little later on.
The discovery of the X-ray led a friend of Madame Curie to investigate the light-giving properties of phosphorescent substances. This young scientist, Monsieur Henri Becquerel, used the metal uranium as the subject of his experiment. After exposing a piece of uranium to sunlight he then placed it upon a photographic plate which was thickly wrapped in black paper. When developed, the plate was found to be affected, so there was no doubt but that here was a radiation similar to the X-ray. Becquerel tried again, using thin metal plates instead of black paper, and got a similar result.
On the following day Becquerel meant to try a fresh experiment, but the morning turned out dull, and since there was no sun he thrust the piece of uranium and his photographic plate into a drawer, and, busy with other work, forgot all about them. Days later he opened the drawer, and it occurred to him to develop the plate and see whether there had been any action upon it, even though the metal had not been first exposed to sunlight. He found there had, and so made the discovery that uranium itself gave off rays capable of penetrating dark matter. Becquerel told Madame Curie of his discovery, and she, greatly interested, set herself to examine other substances and see whether any besides uranium possessed radioactive properties. She did find one in the shape of thorium— a rare earth used in making incandescent mantles; and presently a second, namely, pitchblende, which is the parent ore from which uranium is obtained, and in this— imagine her amazement!—the degree of activity was no less than four times as great as that due to the uranium contained in the sample. The conclusion was plain, namely, that pitchblende must contain some other substance, probably an element, which was more radioactive than uranium.
At once Madame Curie decided that she would discover the nature of this substance, and she and her husband began work. The material for the experiment was presented to Madame Curie by the Austrian Government. It was a ton of pitchblende from the Government’s own mines. Pitchblende is one of those raw materials which are a natural storehouse of many different prime substances, and the task of separating all of these out of twenty hundredweight of hard rock was a tremendously heavy one. It required large quantities of coal, great tanks of distilled water, and many costly chemicals. Above all, it required much knowledge, extreme care, and weeks of very hard work.
Beginning work in a large building, the mass of material slowly decreased until the test tubes of the Curies’ laboratory could hold the results. Then came Madame Curie’s first discovery—that of a new element, which she named polonium, after her native country. But electroscope tests showed that there was a still more active element in the residue, and for months the patient investigators hunted it until, in 1898, they separated out that most marvellous of all elements, radium. Radium proved to be two and a half million times more active than uranium. It not only affected photographic plates, but ironized the air, excited phosphorescence, and liberated heat. It was even able to destroy life, although this knowledge came later.
The Curies did not invent radium, for radium is as old as the world. What they did was to discover it, and this is generally allowed to be the greatest chemical discovery made by man. While the element itself is capable of performing what seem like miracles, its principal value is the light which radium throws upon the structure of the atom and other deep secrets of chemistry.
In 1903 Madame Curie was awarded a doctor’s degree by the University of Paris, the Davy Medal was awarded to her husband and herself, and they also received one of the Nobel prizes. In 1906 Professor Curie was killed in a street accident, and Madame Curie succeeded to his professorship at the University.
Many other scientists have been busy investigating the properties of radium. It was Becquerel who, quite by accident, discovered the fact that the element can burn. He had been carrying an atom of radium salts no bigger than a pinhead in a glass tube in his pocket, and presently discovered a sore place on his body just behind the pocket. It was soon proved that radium rays produce very remarkable results upon animal cells, and one of the first discoveries made was that radium is a cure for warts. One good application of radium puts an end to any wart. From this discovery sprang the radium treatment of cancer and other similar diseases.
Radium, it is now known, emits several different kinds of rays. The Alpha rays are stopped by a sheet of paper, the Beta rays by a thin sheet of tinfoil, but the Gamma rays will penetrate a steel bar or a door. It is to the great English scientist Sir Ernest Rutherford that science owes its knowledge of these different rays. The Alpha rays he showed to be positively charged particles shot out at a velocity of about twenty thousand miles a second. The amazing part about them is that they have been proved to be positively charged atoms of helium, and so, for the first time in the history of the world, the old dream of the alchemists has come true, and we can watch one element change into another. Beta rays consist of streams of electrons traveling at much greater speed, while the Gamma waves are waves in ether similar to X-rays, but shorter.
When radium was first isolated from pitchblende this was supposed to be the only source from which it could be obtained. It is now known that, so far from being confined to one particular geological formation, radium exists everywhere in all rocks and in most water. True, the quantities are very small, for even in pitchblende, which is richer in radium than any other deposit, radium exists only to the extent of one part in two millions. And so difficult is it to obtain that thirty tons of pitchblende yield only one tenth of an ounce (about one part in eleven millions) after operations lasting for more than two years. In the year 1921 the women of America presented Madame Curie with a gramme (about a thimbleful) of radium. In order to obtain this amount six hundred tons of ore were treated, and the labor of five hundred men was required for six months. The process of extracting this tiny amount of radium consumed ten thousand tons of distilled water, a thousand tons of coal, and five hundred tons of chemicals. Is it to be wondered at that diamonds or rubies are cheap as dross when compared with the value of radium?
Whether radium will ever be extracted in quantities large enough for commercial use is a question that at present is without answer. Even if we do find ways of obtaining radium by the pound instead of the milligramme, such large masses would be dangerous to handle.
On the other hand, the X-ray discovered by Professor Röntgen has scores of different uses, and fresh ones are constantly being discovered. The post office, for instance, finds it invaluable. Dangerous drugs, such as cocaine, used to be sent through the post, most carefully hidden. A favorite hiding place was a book. the center of which
was hollowed out and the drug placed in the cavity. Formerly the postal officials took an immensity of time and trouble in their search, and if mistaken were often obliged to pay damages to the owner; to-day the X-ray reveals in a moment if any smuggled object is hidden in an innocent-looking package.
Cigar manufacturers are using the X-ray for killing small insects which bore holes in cigars. The cigars, packed and ready for shipment, are run through a leadlined chamber upon a continuous belt; they remain about five minutes under the rays, and this destroys the insects or their eggs.
All sorts of clever frauds are made up for sale to collectors, especially mummies. In old days it was next to impossible to discover these frauds, but now the eye of the X-ray camera detects them in a flash. Indeed, the X-ray has almost destroyed the once considerable trade in fraudulent mummies, and it has actually hit the drug smuggler much harder than all the legislation on the subject.
Not only surgeons, but dentists, find the X-ray of the greatest value, for by the use of a radiograph the state of the roots of a tooth can be seen without pulling it out of the jaw. Even shoemakers use X-rays; a customer may be shown the bones of his or her foot after a new shoe has been fitted.