The production of radium from uranium is usually stated in milligrams or grams, and even in the richest ores there is usually only a small fraction of a gram to a ton, while in the ordinary lower-grade ore there are only a few milligrams to a ton, corresponding to a small fraction of a grain to a ton. Less than twenty years ago it was estimated that probably not one gram of radium element in the form of its refined salts had been extracted in the world. Today a great many times, perhaps a hundred times or more, this amount has been extracted and is in use. The annual production of radium today in the world is probably several grams. The annual production of uranium in the world is probably several hundred pounds.
The unique position of uranium as the source of radium in nature makes it necessary to discuss both materials together.
Uses of Radium.
—Radium is a heavy white metal which is very unstable, and alters rapidly in the air. It is not used in its metallic stage but only in the form of its salts. A few years ago these salts were supposed to have a general beneficial effect in the treatment of cancer and other malignant growths, but more recent investigations seem to confine their influence to only certain forms of these afflictions. Their influence in other diseased conditions is often very marked, but the full extent of the field of usefulness of radium for medical purposes has not yet been very clearly defined.
In recent years radium has been applied to other important purposes, especially in luminous paint for watches, clocks, compasses and other instruments; and this use has so greatly increased in recent years, especially for military purposes, that it now consumes more radium than is used in medicine. Radium salts are more or less luminous when seen in a darkened room, and this quality is often increased by the admixture of certain other materials, notably zinc sulphide. Hence their value in luminous paints. Radium salts also cause certain minerals to fluoresce, notably the zinc minerals willemite and sphalerite. In Germany, where radium during the war became scarce on account of the shortage of the ores from which it is extracted, radium salts are said to have been preserved for medical purposes, and mesothorium and other radioactive substances used in making luminous paints.
Uses of Uranium.
—Uranium is a heavy white metal, which slowly tarnishes on exposure to the air. The chief use of uranium today is as a source of radium. For many years before the discovery of radium, however, uranium compounds were used in a small way in coloring glass and porcelain, in photography, in reagents for chemical analysis, in mordants for dyeing and for other minor purposes. The use of uranium metal in small quantities in steel manufacture has been tried with some degree of success.
ORES OF RADIUM AND URANIUM
General Statement.
—The principal uranium minerals at present known in nature, which are therefore the principal sources of both uranium and radium, are carnotite and uraninite, with the impure amorphous form of uraninite known as pitchblende. Torbernite, autunite and some of the rarer uranium minerals have produced a little radium and uranium.