Only a few of the interesting deductions possible from this table can be pointed out. On account of the genetie relationship between radium and uranium, the former will be found in nature only when associated with the latter, and always in the same ratio, namely, that of the two life periods to each other, or about one part of radium to three million parts of uranium by weight. This fact has been veri fied by examination of different uranium 'minerals from various parts of the world.
Whenever an atom emits an alpha particle it loses an atom of helium and hence its atomic weight is diminished by four units and its chemical valency by two units. The emission of a beta particle causes no change in atomic weight (since the mass of the beta particle is only one-seventeen hundredth of the atom of hydrogen), but the valency increases by one unit. These changes in atomic weight can be traced out in the accompanying table. That the atomic weight actually changes according to the theory has been verified experimentally for the atomic weights of uranium, radium and radium G (radiolead).
Radium The first disintegra tion product of radium is the only gaseous member of this series. It is given off from all solutions or fusions containing radium, and more or less freely from radium salts and ores. It has been estimated that the total quantity of radium emanation in the atmosphere cor responds to grams of radium. Radium emanation was named niton (shining) by Sir William Ramsay, signifying its property of emitting light; and also by the termination on that it belongs to the series of noble gases such as argon, krypton and xenon. Radium emanation is used in measuring small quantities of radium, also for therapeutic purposes fre quently where the element itself was formerly used. On account of its very short life compared with the parent radium it must be collected at frequent intervals from the parent solution of radium salt to compensate its rapid rate of de cay. Since the gas has all the properties of an ordinary gas it diffuses, when not confined to the surroundings and deposits its solid disin tegration products, radium A, B. etc., on any object, thus imparting apparently radio active properties termed einduced but now more correctly referred to as active deposit. The first three members below emana tion in the series, radium A, B and C, accumu late in a confined volume to maximum quantity 'in about four hours.
The practical uses of radium are confined to two classes: (1) therapeutic and (2) for the production of luminous products by mix ing with phosphorescent zinc sulphide. The therapeutic use of radium was suggested by the physiological effects of its rays which are very marked. Prolonged exposure to large quantities of radium produces painful and even fatal burns. By controlling the quantity of radium, the time of exposure and the thickness of metallic screening, radium may be used for the treatment of malignant growths, such as cancer, through the effect of its Ldiations.
Some remarkable results have been achieved in this direction but much experimentation is re quired to determine all the physical factors in volved in obtaining the best results. Radium therapeutics may still he regarded as in the ex perimental stage, and is much hampered by the scarcity and high cost of radium.
By mixing a small proportion of radium with an especially prepared phosphorescent zinc sulphide, a fairly permanent luminescent material is produced which can be applied to the dials of instruments or to any other sur face which it is desired to render self-luminous in the dark. During the European War such material was extensively employed on airplanes, battleships and in the trenches since it had the advantage of illuminating dials, gun sights, etc., without exposing a light to the enemy, since the luminosity, even that from the strongest preparations, can be seen at a distance of only a few yards. The proportion of radium em ployed in preparing the luminous materials de pends on the luminosity desired. About one part of radium element per 4,000 parts of zinc sulphide is the upper limit for radium. Much lower mixtures than this can be used for many purposes. The luminosity of radium paint in creases for about three weeks after prepara tion and then falls off for some months, finally reaching a value about 20 per cent of the orig inal brightness which appears to remain con stant for several years at least.
The natural sources of radium are prin cipally the three uranium ores — carnotite, uraninite (pitchblende) and autunite. Carnotite (a vanadate of uranium) is found extensively in the arid regions of southwestern Colorado and southeastern Utah and now constitutes by far the most important source of radium. It is estimated that more than 55 grams (or about two ounces) of radium element have been pro duced from this source. The principal source of pitchblende has been the Austrian mines of Saint Joachimstahl. Some radium has also been prepared in France from autunite (a phosphate of uranium, found in France near Autun and also in Spain. See RADioacriviTv; POLONIUM; URANINITE ; URANIUM, etc.
Bibliography,— Curie, Madame, de radioactivite) (2 vols., Paris 1910); Gager, C. S., (Effects of the Rays of Radium on Plants> (New York 1908) ; Meyer and von Schweidlees recent work on radioactivity; Rushy, H. H. (in New York Botanical Gardens Journal, Vol. XVI, New York 1915) ; Rutherford, Ernest E., (Radioactive Substances and their (Cambridge 1913) ; Soddy, F., (Chemistry of the Radio Elements) (2 parts, London and New York 1914). Consult also the following periodi cals: Philosophical Magazine (London). Le Radium (Paris), Comptes Rendus de Mcadensie (Paris), Slteungsbericitte (Vienna Academy), American Journal of Science (New Raven), Journal of the American Chemical Society (New York), Journal of the Chemical Society don, Berichte d. deutsch chem. Gets: ().