The wonders of radium

The extraction process consists in eliminating the various substances in the ore until only the radium salts are left. But, in the case of carnotite, more than 900 different operations, requiring six months of labor, are required between the digging of the ore and the production of a gram of pure radium salt. A solution containing barium and radium salts in the ratio of ten parts of radium to a billion is treated with sulphate to precipitate an insoluble “raw sulphate of barium.”

Radium ores are generally found in connection with granitic masses—i.e., in places where granite forms at least part of the rock of the country. The carnotite ore usually consists of a thin layer of sandstone which crops out on the side of a canyon wall and is recognized by the characteristic sulphur-yellow color. The narrow seams are usually in the form of pockets, so that the value of a claim is dubious until it has been thoroughly explored and worked.

Most of the original radium minerals, such as uraninite, samarskite, and brannerite, are black and have a shiny fracture and a high specific gravity. These minerals are, however, rarely found in commercially valuable quantities.

Pitchblende, the richest source of radium, has the same composition as uraninite and the same general appearance, except that it shows no crystal form. It occurs in veins. There are extensive deposits of pitchblende or uraninite at Joachimstahl, Bohemia (Czecho-Slovakia), containing from 30 to 70 per cent uranium oxide, from which the radium is extracted. But here the uranium ore occurs in small pockets in widely separated localities, so that it is merely a by-product of other mining operations. However, after separation of the uranium from the ore, the residues are three to five times as radioactive, weight for weight, as the uranium. The amount of radium in old unaltered mineral is always proportional to its content of uranium in the ratio of 3.3 parts of radium by weight to ten million parts of uranium.

New radium ore fields were discovered in Czecho-Slovakia in 1922. The production of radium in that country increased from .7746 gram in 1911, to 1.7118 grams in 1915, and 2.2310 grams in 1920. In 1922, steps were taken to modernize the plants in the Jachcymov district (Bohemia), where the known supply will last 20 years at the present rate of production—a little more than two grams a year.

The famous Joachimstahl pitchblende deposits were a monopoly of the Austrian Government before the World War, but they are now being worked by the Imperial and Foreign Corporation of London, under an agreement with the Czecho-Slovak Government. In 1922 a loan of two grams of radium (valued at more than $300,000) was made to Oxford University, for a period of fifteen years. This material is being used for experimental purposes by Prof. Frederick Soddy, of Oxford, and his associates. It has been stated that one of the chief objectives is the discovery of a method for the release and control of intra-atomic energy.

Pitchblende has been found in only a few places—in Bohemia (Czecho-Slovakia), southern Saxony, Cornwall, and Gilpin County, Colorado. So far, this ore has not been the source of any radium produced in this country.

When the original radium minerals (uraninite, samarskite, brannerite, etc.) break down through weathering, other radium minerals are formed from them, such as autunite, trobernite, carnotite, and tyuyamunite. The two latter ores are the most widespread and abundant. Autunite, a phosphate of calcium and uranium, is as active as uranium. Carnotite and tyuyamunite cannot be distinguished visually from each other. Both are a bright canary-yellow in color, and are powdery, finely crystalline, or, rarely, clay-like in texture. Both these minerals are found in the same section of Utah and of Colorado, usually associated with fossil wood and other vegetation, in friable, porous, fine-grained sandstone.

The only other deposits that yield tyuyamunite in marked quantity are those of Tyua-Muyun, in the Andiyan district, Ferghana Government, central Asiatic Russia (Russian Turkestan), where it occurs with rich copper ores in a pipe in limestone.

The radium salts—hydrous sulphate, chloride, or bromide—are all white or nearly white substances, no more remarkable in appearance than common salt. Neither radium nor the radium minerals are in themselves luminescent. Tubes containing radium salts glow because they include impurities which the invisible radiations from the radium cause to give light. The pure radium metal has been isolated only two or three times, and few persons have seen it.

NEW SOURCES OF RADIUM

In 1921, a rich deposit of pitchblende was discovered in the province of Ontario, Canada. Since 1921 there has been a rather considerable exportation of radioactive minerals from Madagascar; and in 1922 deposits of uranium oxide (U₃O₈) were discovered in Switzerland. During the same year an unknown Belgian traveler sold to a curio dealer a strange stone picked up in the Congo. The dealer sold it to the British Museum. Upon examination the stone was found to be radioactive. Belgian geologists were immediately informed, and a Belgian mission was sent to the Katanga district, where the stone was found. Two veins of chalcolite (torbernite) containing substances rich in radium were soon located by the geologists, one near the Portuguese frontier. Chalcolite, the crystallized phosphate of copper and uranium, is twice as active as uranium.

The newly discovered mineral has been given the name “curite,” in honor of Mme. Curie, the discoverer of radium. These deposits are now known to be the richest in the world. And, what is hardly less important, the radium may be isolated by simple dissolution in nitric acid, even in the cold. It is also readily dissolved in warm hydrochloric acid. Only 15 tons of the ore need to be treated to produce a gram of radium.

Curite is found in three forms, as translucent reddish brown needle-like crystals; as compact saccharoid crystalline aggregates, orange in color; and as orange-colored earthy masses surrounding the preceding variety. The chemical composition is expressed by the formula 2(PbO)5(UO₃)4(H₂O).

In 1924 a pitchblende deposit, very rich in radium, was discovered in Ferghana, in Russian Turkestan. Soviet Russia is now mining the ore and extracting the radium, which is kept at the Radium Institute of the Academy of Science.

Curiously enough, more than $500,000 worth of radium has been added to the world’s store of this valuable element by “boiling down” British cannons used in the World War. No fewer than five grams—less than a tablespoonful—have been secured by British scientists by this process. The radium is stored in a lead safe weighing almost two tons—a container which was invented by a Dr. Kuss, and the composition of which is known only to himself. One of the greatest difficulties of scientists has been to find some material which would prevent the constant bombardment of the radium rays.

One important result of these recent discoveries—especially that of the Congo deposits—is that the price of radium dropped $30,000 a gram, and sells now at the rate of $70,000 a gram instead of some $100,000. The Standard Chemical Company of Denver, Colorado, has been obliged to close down its three-story laboratory, which until the close of the year 1922 had, for several years previously, been producing a million dollars’ worth of radium annually. The Paradox Valley carnotite ore cannot be worked in competition with the rich deposits of the Belgian Congo. It has been stated that five pounds annually could be produced from these Congo deposits. The Colorado company had been selling at the rate of $58,500,000 a pound. The Congo company can profitably sell the precious element at $29,250,000 less a pound.

So, unless war breaks out again to prevent shipments from abroad, the United States of America will produce no more radium for a long while to come.

THE RADIOACTIVE DISINTEGRATION SERIES

In order to show the decomposition products of the two parent radioactive elements—Uranium and Thorium—and their chief characteristics, together with their relations to one another, and the time required for the product (element) to be half transformed, it is customary to arrange them in a disintegration series. There are three series, Uranium I, Uranium Y, and Thorium.

In the first table given below is shown how the series known as Uranium I is transformed into the end-product, uranium lead. This is followed by the Uranium Y (or Actinium) series, and by the Thorium series; the end-product of all three being a characteristic type of lead. In the tables T is the “time-period” of a product, or the time required for the product to be half transformed. In the column “Rays” is shown what type of ray, or rays, is, or are, emitted during the disintegration process—A=Alpha rays (or particles), B=Beta rays (negative electrons), and G=Gamma rays (or X-rays of very high “frequency”).

“In the great majority of cases,” says Sir Ernest Rutherford, “each of the radioactive elements breaks up in a definite way, giving rise to one Alpha or Beta particle and to one atom of the new product. Undoubted evidence, however, has been obtained that in a few cases the atoms break up in two or more distinct ways, giving rise to two or more products characterized by different radioactive properties. A branching of the uranium series was early demanded in order to account for the origin of Actinium.”

In the first column is given the “atomic weight” of each radioactive element, the weight decreasing with (almost) every “disintegration period.” The figures followed by an interrogation point are Rutherford’s, and indicate that slightly different figures are given by other authorities.

URANIUM I SERIES

URANIUM Y (ACTINIUM) SERIES

THORIUM SERIES