Radium

RADIUM. BY DR. JAMES E. TALMAGE, PROFESSOR OF GEOLOGY,

UNIVERSITY OF UTAH.

It is in response to a special request from the Editor of the Era that the writer ventures to present a short article on this in- teresting topic; for he freely acknowledges that to him so little is

known regarding this new and strange element that to voluntarily appear in print on the subject would be presumptuous. The inter- est of scientists and of thinking people of all classes has been aroused over the announcement of the discovery of a new element in nature, the properties of which appear to be not only marvelous and novel, but in some respects seemingly contradictory of our fundamental conceptions regarding matter and force. Radium has been described as the most powerful of all known radio-active substances; it may be well therefore to enquire first

as to the nature of radio-activity in general. For nearly a decade past it has been known that a few substances have the property of emitting continuously certain rays of force which act in some of their effects like light rays, though they penetrate bodies that are opaque to ordinary light. These strange rays act upon a photo- graphic plate as does light; but the plate-holder used with the camera is no protection against them, for they penetrate the wood and hard rubber, and affect the plate as if it had been exposed uncovered. Even a casing of thin metal fails to stop these rays, though thick metal, particularly lead, is an effective barrier to the passage of the rays for short periods of time. Furthermore, these rays render the air and other gases through which they pass, pow- erful conductors of electricity. Unlike light, these new rays can-

not be reflected or refracted by ordinary means. In 1896, Bec- querel, a scientist of acknowledged ability, demonstrated that the somewhat rare metal uranium, and all its compounds, emit these rays continuously. They are known as the Becquerel rays. A radio-active substance, therefore, is one that is capable of spon- taneously emitting Becquerel rays. By the labors of Schmidt, M. and Mme. Curie of Paris, and Debierne, it has been proved that in addition to uranium, other elements such as thorium, polonium, and the newly discovered actinium and radium are strongly radio-active- Practically all of these radio-actives are associated in nature with the uranium minerals, occurring therewith in quantity infini- tesimally small. Polonium is found with bismuth in association

with uranium minerals; it has not been clearly proved that poloni- um is indeed a separate and new element. Actinium occurs with elements of the alkali- earth group in uranium minerals, and ra- dium is associated with barium in the same class of minerals. In a general way the degree of radio-activity possessed by any mineral or mixture of minerals is in direct proportion to the amount of the radio-active element present. The discovery of radium was facilitated by the knowledge of this fact. To M. Curie and his talented wife is due the honor attached to this important dis-

covery. In 1898 Mme. Curie was engaged in research as to radio- activity among the elements. She demonstrated that but very few elements are even feebly radio-active; but to her surprise she found certain uranium minerals (notably pitchblende, or uraninite, and carnotite) to be more strongly radio-active than the contained amount of uranium would explain. This led to a search for un- known radio- actives in the uranium minerals; and radium was found —the only strongly radio-active substance thus far fully proved to be a new element. As stated, it exists in very small quantity in the uranium minerals; and moreover, the process of ex- traction is long, tedious, and expensive; the product therefore is

of high cost. In France, radium is obtained from the residues left after extracting the uranium from pitchblende; and according to M. Curie's statement these residues contain from two to three deci- grams (three to four grains) of radium per ton. Much has been said through newspapers and magazines regarding the fabulous

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cost of this rare product. Statements of cost at so much per ounce or pound are practically meaningless, unless the intensity of the radium mixture is specified, as the radio-activity depends upon the actual amount of the radium element present. A prominent busi- ness firm dealing in chemical supplies recently offered the writer ten milligrams (about fifteen hundredths of a grain) of radium ba- rium chloride for three hundred dollars. This was guaranteed to possess a radio-activity of one million; that is, it was a million times as strong in radio-active properties as metallic uranium. This cost is at the rate of nearly two thousand dollars per grain. It is of local interest to note that the radium thus far pre- pared in America has been obtained from uranium ores found in western Colorado and contiguous parts of Utah. The material mostly used is carnotite —a vanadate of uranium and potassium. In the laboratory of the university of Utah the writer has obtained radium chloride by a comparatively simple treatment of a new vanadium-uranium mineral recently discovered in the Uinta moun- tains. Radium, as an element, that is to say, separate and free from all combinations or mixtures, has never yet been prepared. It is

doubtful if any pure compound of this element has been produced. The radium product as prepared is really radium chloride mixed with barium chloride, the radio-active intensity increasing as the contaminating barium salts are removed. Radium-barium chloride of one million five hundred thousand intensity as compared with the uranium standard has been prepared. As to the properties of this newly discovered element, not much is yet definitely known, but the little already proved is sufliciently

astounding. Radium is known to emit spontaneously and without cessation, both light and heat, besides other rays of force not di- rectly observable by the unaided senses, but even more remarkable than the readily recognizable light and heat. A photographic plate, enclosed in the tightest of plate- holders, or protected against light as are the X-ray plates by wrappings of orange and black papers, is affected as if exposed to daylight, when a tube containing a radium compound is brought near, even though the tube be hermetically sealed. The rays so emitted pass through the walls of the sealed tube and penetrate

the wrappings of the plate or the hard rubber slide of the plate- holder. Metals are less readily penetrated by the radium rays than are most other bodies; if therefore metallic objects, such as coins, keys, pieces of sheet lead, etc., be placed between the radium tube and the plate, a picture of these objects appears when the plate is developed in the usual way. Such a picture is in reality a shadow-graph, the part of the plate protected by the metal piece being unaffected by the radium rays, while the unprotected parts are acted upon as if by light. To produce such a picture, an ex- posure of hours, days, or weeks may be required, according to the radio-active intensity of the radium-bearing material. Now, as stated, uranium and other radio-actives, behave in a similar way. Radium, however, emits not only Becquerel rays, acting through glass, paper, etc., but, in addition thereto, emana- tions of substance analagous to a highly attenuated gas, which emanations do not penetrate solid bodies, but which may be con- ducted through a tube as may any gas. The writer has produced scores of shadow-graphs as described, using radium-bearing mate- rial of low intensity obtained from Utah minerals; and has also produced pictures by the emanations from the same material, by employing the following simple process: A glass bulb containing a small amount of radium-bearing chloride was placed inside a thick- walled cylinder of lead. The cylinder was closed below by a base of thick lead, and above by a lid of the same material. The lid was perforated to admit the end of a glass tube about six inches long bent at a right angle; the inner end of this tube was at- tached by hermetic sealing to the bulb containing the radium. The tube was bent downward near its outer end, and was secured in the mouth of a bottle by a tightly-fitting rubber stopper. Inside this bottle a photographic plate was placed, properly protected by opaque wrappings against any possible effect of ordinary light; on this plate, outside the paper wrapping, a disc of metal v/as held in place by a rubber band. Plates similarly prepared were placed inside the lead cylinder, and others were held in place on the out- side of the cylinder.After an exposure of a few days, during which the apparatus was kept in a light-tight box, the plates were developed. Of course, the plates from the inside of the cylinder showed the usual shadow- graphs— due to the radiations from the

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radium inside the bulb, which radiations had to penetrate the glass walls of the bulb and the several layers of paper covering the plates. The plates held in contact with the outside of the lead cylinder showed no picture, plainly proving that the radiations had failed to penetrate the leaden walls. But the plate from the bottle showed the strongest picture of all. This effect must be due to the emanations of actual substance from the radium passing through the twice-bent tube, and reaching the plate in the bottle. Radium compounds of high intensity emit light rays continu- ously. Of this phenomenon M. Curie has written: "The salts of radium are spontaneously luminous. It might be said that they make themselves luminous by the action of the Becquerel rays they emit. Anhydrous chloride and bromide of radium are the salts that give the most intense luminescence. They may be ob- tained so luminous that the light can be seen in full daylight. The light emitted by the salts of radium recalls in tint that from a fire fly. The luminosity of the radium salt decreases with time with- out ever completely disappearing, and those that were colorless at first become gray, yellow or violet."*

Many substances, both mineral and organic, become luminous if brought near a tube containing radium; among such are zinc silicate, zinc sulphide, and the diamond. This effect may be util- ized as a means between true diamonds and of distinguishing spurious imitations, the real gem becoming strongly phosphores- cent, while the paste counterfeit remains dark and dull in the presence of the searching radium rays. A new device, known as the spinthariscope, reveals in a very pretty way the effect of radi- um inducing luminosity in other bodies. A small amount of the sensitive material, zinc sulphide for example, is spread upon a metal surface, called the screen; a of radium is placed particle upon this, or is held about a sixteenth of an inch above the pre- pared surface. If the screen be then examined through a lense of medium power in a dark room, a marvelous sight presents itself. The surface of the screen appears blazing with luminous points, apparently in rapid motion. The appearance has been likened by some to that of a shower of meteorites, and by others to the

See American Chemical Journal, April, 1904, page 422.

694 IMPRO VEMENT ERA.

luminous streaming of the aurora borealis. No observer who has once witnessed this blazing display of atomic activity will soon forget the impressive effect. The luminosity of the screen ap- pears to be the result of an actual bombardment of the phosphor- escent material by emanations from the radium. But not only is radium capable of exciting luminosity in other bodies, it imparts to its surroundings the radio-active power in practically all of its phases. Thus, a box of paper, wood, or metal, in which a sealed tube containing radium has been allowed to lie, becomes so radio-active as to readily affect a photographic plate, and may retain this property for days and weeks. The walls and furniture of a laboratory in which radium experiments have been conducted, and even the persons and clothing of the operators, become thus excited to radio-activity. As before stated, radium compounds emit ordinary heat rays; this they do continuously, and seemingly without loss of sub- stance. The heat so radiated has been carefully measured, and we know with fair accuracy the powers of the new element in this respect. M. Curie demonstrated that seven-tenths of a gram of radium bromide inclosed in a small bottle maintained a tempera-

ture three degrees higher than that of another bottle contain- ing no radium but otherwise kept under the same conditions. As to the quantity of heat thus liberated, it has been demonstrated that radium gives off continuously heat sufficient to melt its own weight of ice every hour. Freshly prepared radium salts emit but little heat; their power in this respect increases with time, until a maximum effect is reached in about a month, after which the heat radiations are practically constant. Radium rays produce certain physiological effects. If a ves-

sel containing a radium salt be brought near the closed eyes or placed against the side of the head, the eye itself becomes lumi- nous and the sensation of light results, though in reality the light is developed within the eye. As to the effect of these rays on the tissues of the body, M. Curie has written: "The rays of radium act on the epidermis. If we place on the skin for a few minutes a bulb containing radium no particular sensation is felt. But fifteen or twenty days afterward it produces a reddening of the skin, then a slough in the place where the bulb was applied. If

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the action of the rays be long enough there is finally formed a sore that takes several months to heal. The action of the rays from radium is analogous to that produced by the Roentgen rays. The attempt has been made to utilize this action in the treatment of lupus and cancer. The radium rays also act upon the nervous centers and cause paralysis and death."* The eminent investigator spoke from painful experience in describing the sores produced by radium. Prof. Becquerel is said to have suffered for weeks from a painful and dangerous slough- ing sore on the body resulting from carrying in his waistcoat pocket a small tube containing radium. Plainly then, radium is a dangerous substance to handle. According to present knowledge on the subject, leaden vessels with thick walls are the safest con- tainers of radium tubes. It is surprising that the destructive effects of radium rays on the body tissues are not apparent until days after exposure. Experiments have been conducted to determine the effect of radium rays on the lower animals. M. Danysz is prominent in this part of the investigation. He suspended a tube containing a frac- tion of a grain of radium chloride over a cage of mice. The tube was removed after three days. Soon after, the mice began to shed their fur; some of them became blind, and one by one they died. Fatal effects were produced among chickens, guinea pigs, rabbits and other animals. Plant tissues are destroyed by a short exposure to radium compounds. Among the most surprising of these physiological effects are the instances of arrested development resulting from radium ex- posure. It is reported that M. Danysz exposed the larvse of a small moth to the radium rays for a few hours. In the course of several weeks most of the larvis so exposed died, but a few lived on, as larvse. Other larvse of the same colony, which had not been exposed to the radium, passed into the pupa stage, emerged as moths, produced eggs which in turn developed another gener- ation of larvse, pupte, and moths; and so on through a third gen- eration, while the larvse that had been exposed to the radium con- tinued to live as larvae without progress or development. Modifi-

• See American Chemical Journal, before cited, pages 422, 423.

cation of form among certain animals has been effected by radium rays, such as to produce aberrant individuals suggesting new species. An experiment recently conducted by the writer is somewhat interesting, though not productive of significant results. Some small white ants, (termites) we^e secured, with a quantity of the earth-mold in which they had lived. A hundred termites were placed in each of four small dishes, each dish was set in an outer vessel containing a little water, and loosely covered with a glass disc. This arrangement prevented the earth from becoming dry. A tube containing about a tenth of a grain of weak radium chloride was left for a few hours over one of the vessels; a second vessel was similarly exposed; while the other two were kept away from radium. On the day following, about half the termites from the vessels subjected to the radium had crawled out of the inner dish and were floating on the water in the outer vessel. They were returned to the inner dish. A day later over eighty in one dish, and more than fifty in the other were found floating on the water, some of them dead. The living ones were again replaced. None escaped into the water after this, but they gathered on top of the mold in the dish and many died. In the case of the two lots not exposed to the radium rays, none left the inner dish, and they lived in ap- parent comfort, mostly beneath the surface of the mold. One of these lots was then exposed to the radium tube for two hours. Later in the day twenty-four of the termites had crawled from the inner dish and were floating on the water in the outer vessel. During the experimenter's absence from the laboratory for a few days following the last observations, the water in the vessels dried away and the test was thus brought to an end. It is evident that the ants experienced a disagreeable effect from the rays, — whether analogous to light, heat, or some other manifestation of force, we — may not know, and that they tried to get away from the disturb- ing cause.

One of the first questions asked by those whose interest has been awakened regarding radium is this —What is the stuff like? Radium-barium chloride —the commonest of radium preparations is a white crystaline powder, not unlike ordinary table salt.

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Another common query is: Of what use is radium? The truthful answer is that at present radium has no practical use. The fact that the substance emits both light and heat has given rise to the popular supposition that it may be used for actual

lighting and heating purposes. As already shown, even weak radium salts are destructive to animal tissues, and continued ex- posure to radium rays would be fatal to man and animals. Radium preparations of sufficient intensity and in quantity adequate to produce light and heat for house use would be death-dealing. Is radium then useless? No, its possibilities have not yet been developed; its latent usefulness has yet to be discovered. When one of skeptical mind was heard to speak contemptuously of Montgolfier's balloon experiments, and asked to what use such could lead, Benjamin Franklin replied with the question, "Of what use is a new-born babe?" In the treatment of disease, and in the destruction of bacteria, radium has not yet been successfully employed, and the expecta- tions in this respect aroused by early announcements of its prop- erties have not been realized. But we know as yet little of what radium can do. The demonstration that radium emits light and heat, spon- taneously and continuously, and without diminution of substance as far as we can determine, has led to the hasty and unwarranted inference that we are here confronted with an actual creation of force without expenditure of substance. The indestructibility of matter and force, and the conservation of energy, are corner- stones of the edifice of modern science; and these have not been dis- turbed by this new discovery. The forces with which we are most familiar, — — example are mutually con- light, heat, electricity, for

vertible. They, together with sound, and mechanical energy, are but as the different kinds of money — silver, gold, bank-notes

each exchangeable on a basis of mathematical exactness for any other. So, too, the precise amount of heat represented by a given expenditure of energy of other kinds can be calculated and pro- duced. It is well known that there are substances possessing the power of absorbing certain kinds of energy, and returning the same in the form absorbed, or as some other manifestation of force. Thus, barium sulphide and other bodies become highly luminous