Experiments of Becquerel—Work of the Curies—Discovery of
Radium—Enormous Energy—Various Uses.

Early in 1896 just a few months after Roentgen had startled the scientific world by the announcement of the discovery of the X-rays, Professor Henri Becquerel of the Natural History Museum in Paris announced another discovery which, if not as mysterious, was more puzzling and still continues a puzzle to a great degree to the present time. Studying the action of the salts of a rare and very heavy mineral called uranium Becquerel observed that their substances give off an invisible radiation which, like the Roentgen rays, traverse metals and other bodies opaque to light, as well as glass and other transparent substances. Like most of the great discoveries it was the result of accident. Becquerel had no idea of such radiations, had never thought of their possibility.

In the early days of the Roentgen rays there were many facts which suggested that phosphorescence had something to do with the production of these rays It then occurred to several French physicists that X-rays might be produced if phosphorescent substances were exposed to sunlight. Becquerel began to experiment with a view to testing this supposition. He placed uranium on a photographic plate which had first been wrapped in black paper in order to screen it from the light. After this plate had remained in the bright sunlight for several hours it was removed from the paper covering and developed. A slight trace of photographic action was found at those parts of the plate directly beneath the uranium just as Becquerel had expected. From this it appeared evident that rays of some kind were being produced that were capable of passing through black paper. Since the X-rays were then the only ones known to possess the power to penetrate opaque substances it seemed as though the problem of producing X-rays by sunlight was solved. Then came the fortunate accident. After several plates had been prepared for exposure to sunlight a severe storm arose and the experiments had to be abandoned for the time being. At the end of several days work was again resumed, but the plates had been lying so long in the darkroom that they were deemed almost valueless and it was thought that there would not be much use in trying to use them. Becquerel was about to throw them away, but on second consideration thinking that some action might have possibly taken place in the dark, he resolved to try them. He developed them and the result was that he obtained better pictures than ever before. The exposure to sunlight which had been regarded as essential to the success of the former experiments had really nothing at all to do with the matter, the essential thing was the presence of uranium and the photographic effects were not due to X-rays but to the rays or emanations which Becquerel had thus discovered and which bear his name.

There were many tedious and difficult steps to take before even our present knowledge, incomplete as it is, could be reached. However, Becquerel's fortunate accident of the plate developing was the beginning of the long series of experiments which led to the discovery of radium which already has revolutionized some of the most fundamental conceptions of physics and chemistry.

It is remarkable that we owe the discovery of this wonderful element to a woman, Mme. Sklodowska Curie, the wife of a French professor and physicist. Mme. Curie began her work in 1897 with a systematic study of several minerals containing uranium and thorium and soon discovered the remarkable fact that there was some agent present more strongly radio-active than the metal uranium itself. She set herself the task of finding out this agent and in conjunction with her husband, Professor Pierre Curie, made many tests and experiments. Finally in the ore of pitchblende they found not only one but three substances highly radio-active. Pitchblende or uraninite is an intensely black mineral of a specific gravity of 9.5 and is found in commercial quantities in Bohemia, Cornwall in England and some other localities. It contains lead sulphide, lime silica, and other bodies.

To the radio-active substance which accompanied the bismuth extracted from pitchblende the Curies gave the name Polonium. To that which accompanied barium taken from the same ore they called Radium and to the substance which was found among the rare earths of the pitchblende Debierne gave the name Actinium.

None of these elements have been isolated, that is to say, separated in a pure state from the accompanying ore. Therefore, pure radium is a misnomer, though we often hear the term used. [Footnote: Since the above was written Madame Curie has announced to the Paris Academy of Sciences that she has succeeded in obtaining pure radium. In conjunction with Professor Debierne she treated a decegramme of bromide of radium by electrolytic process, getting an amalgam from which was extracted the metallic radium by distillation.] All that has been obtained is some one of its simpler salts or compounds and until recently even these had not been prepared in pure form. The commonest form of the element, which in itself is very far from common, is what is known to chemistry as chloride of radium which is a combination of chlorin and radium. This is a grayish white powder, somewhat like ordinary coarse table salt. To get enough to weigh a single grain requires the treatment of 1,200 pounds of pitchblende.

The second form of radium is as a bromide. In this form it costs $5,000 a grain and could a pound be obtained its value would be three-and-a-half million dollars.

Radium, as we understand it in any of its compounds, can communicate its property of radio-activity to other bodies. Any material when placed near radium becomes radio-active and retains such activity for a considerable time after being removed. Even the human body takes on this excited activity and this sometimes leads to annoyances as in delicate experiments the results may be nullified by the element acting upon the experimenter's person.

Despite the enormous amount of energy given off by radium it seems not to change in itself, there is no appreciable loss in weight nor apparently any microscopic or chemical change in the original body. Professor Becquerel has stated that if a square centimeter of surface was covered by chemically pure radium it would lose but one thousandth of a milligram in weight in a million years' time.

Radium is a body which gives out energy continuously and spontaneously. This liberation of energy is manifested in the different effects of its radiation and emanation, and especially in the development of heat. Now, according to the most fundamental principles of modern science, the universe contains a certain definite provision of energy which can appear under various forms, but which cannot be increased. According to Sir Oliver Lodge every cubic millimeter of ether contains as much energy as would be developed by a million horse power station working continuously far forty thousand years. This assertion is probably based on the fact that every corpuscle in the ether vibrates with the speed of light or about 186,000 miles a second.

It was formerly believed that the atom was the smallest sub-division in nature. Scientists held to the atomic theory for a long time, but at last it has been exploded, and instead of the atom being primary and indivisible we find it a very complex affair, a kind of miniature solar system, the centre of a varied attraction of molecules, corpuscles and electrons. Had we held to the atomic theory and denied smaller sub-divisions of matter there would be no accounting for the emissions of radium, for as science now believes these emissions are merely the expulsion of millions of electrons.

Radium gives off three distinct types of rays named after the first three letters of the Greek alphabet—Alpha, Beta, Gamma—besides a gas emanation as does thorium which is a powerfully radio-active substance. The Alpha rays constitute ninety-nine per cent, of all the rays and consist of positively electrified particles. Under the influence of magnetism they can be deflected. They have little penetrative power and are readily absorbed in passing through a sheet of paper or through a few inches of air.

The Beta rays consist of negatively charged particles or corpuscles approximately one thousandth the size of those constituting the Alpha rays. They resemble cathode rays produced by an electrical discharge inside of a highly exhausted vacuum tube but work at a much higher velocity; they can be readily deflected by a magnet, they discharge electrified bodies, affect photographic plates, stimulate strongly phosphorescent bodies and are of high penetrative power.

The radiations are a million times more powerful than those of uranium.
They have many curious properties.

If a photographic plate is placed in the vicinity of radium it is almost instantly affected if no screen intercepts the rays; with a screen the action is slower, but it still takes place even through thick folds, therefore, radiographs can be taken and in this way it is being utilized by surgery to view the anatomy, the internal organs, and locate bullets and other foreign substances in the system.

A glass vessel containing radium spontaneously charges itself with electricity. If the glass has a weak spot, a scratch say, an electric spark is produced at that point and the vessel crumbles, just like a Leyden jar when overcharged.

Radium liberates heat spontaneously and continuously. A solid salt of radium develops such an amount of heat that to every single gram there is an emission of one hundred calories per hour, in other words, radium can melt its weight in ice in the time of one hour.

As a result of its emission of heat radium has always a temperature higher by several degrees than its surroundings.

When a solution of a radium salt is placed in a closed vessel the radio-activity in part leaves the solution and distributes itself through the vessel, the sides of which become radio-active and luminous.

Radium acts upon the chemical constituents of glass, porcelain and paper, giving them a violet tinge, changes white phosphorous into yellow, oxygen into ozone and produces many other curious chemical changes.

We have said that it can serve the surgeon in physical examinations of the body after the manner of X-rays. It has not, however, been much employed in this direction owing to its scarcity and prohibitive price. It has given excellent results in the treatment of certain skin diseases, in cancer, etc. However it can have very baneful effects on animal organisms. It has produced paralysis and death in dogs, cats, rabbits, rats, guinea-pigs and other animals, and undoubtedly it might affect human beings in a similar way. Professor Curie said that a single gram of chemically pure radium would be sufficient to destroy the life of every man, woman and child in Paris providing they were separately and properly exposed to its influence.

Radium destroys the germinative power of seeds and retards the growth of certain forms of life, such as larvae, so that they do not pass into the chrysalis and insect stages of development, but remain in the state of larvae.

At a certain distance it causes the hair of mice to fall out, but on the contrary at the same distance it increases the hair or fur on rabbits.

It often produces severe burns on the hands and other portions of the body too long exposed to its activity.

It can penetrate through gases, liquids and all ordinary solids, even through many inches of the hardest steel. On a comparatively short exposure it has been known to partially paralyze an electric charged bar.

Heat nor cold do not affect its radioactivity in the least. It gives off but little light, its luminosity being largely due to the stimulation of the impurities in the radium by the powerful but invisible radium rays.

Radium stimulates powerfully various mineral and chemical substances near which it is placed. It is an infallible test of the genuineness of the diamond. The genuine diamond phosphoresces strongly when brought into juxtaposition, but the paste or imitation one glows not at all.

It is seen that the study of the properties of radium is of great interest. This is true also of the two other elements found in the ores of uranium and thorium, viz., polonium and actinium. Polonium, so-called, in honor of the native land of Mme. Curie, is just as active as radium when first extracted from the pitchblende but its energy soon lessens and finally it becomes inert, hence there has been little experimenting or investigation. The same may be said of actinium.

The process of obtaining radium from pitchblende is most tedious and laborious and requires much patience. The residue of the pitchblende from which uranium has been extracted by fusion with sodium carbonate and solution in dilute sulphuric acid, contains the radium along with other metals, and is boiled with concentrated sodium carbonate solution, and the solution of the residue in hydrochloric acid precipitated with sulphuric acid. The insoluble barium and radium sulphates, after being converted into chlorides or bromides, are separated by repeated fractional crystallization.

One kilogram of impure radium bromide is obtained from a ton of pitchblende residue after processes continued for about three months during which time, five tons of chemicals and fifty tons of rinsing water are used.

As has been said the element has never been isolated or separated in its metallic or pure state and most of the compounds are impure. Radium banks have been established in London, Paris and New York.

Whenever radium is employed in surgery for an operation about fifty milligrams are required at least and the banks let out the amount for about $200 a day. If purchased the price for this amount would be $4,000.