WHERE WE GET 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 (U_3O_8) 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(UO_3)4(H_2O).
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
T (average Rays (given out in
Element Atomic time-period--half each
Weight transformed) decomposition)
---------------------------------------------------------------------
Uranium I 238 4.5 × 10^9 yrs. Alpha
Uranium X1 234 23.8 days Beta, Gamma
Uranium X2 234 1.15 min. Beta, Gamma
Uranium II 234 About 2 × 10^6 yrs. Alpha
Ionium 230 About 9 × 10^4 yrs. Alpha
Radium 226 (+) 1700 yrs. Alpha
Niton (Emanation) 222 3.85 days Alpha
Radium A 218 3.05 min. (?) Alpha
Radium B 214 26.8 min. (?) Beta, Gamma
Radium C 214 19.5 min. (?) Alpha, Beta, Gamma
Radium C′ 214 10^{-6} sec. (?) Alpha
Radium D 210 (+) 16 yrs. Beta, Gamma
Radium E 210 (+) 4.85 days Beta, Gamma
Radium F (Polonium) 210 (+) 136.5 days Alpha
Radium G (End-product 206 ............... ...............
uranium-lead)
---------------------------------------------------------------------
URANIUM Y (ACTINIUM) SERIES
T (average Rays (given out in
Element Atomic time-period--half each
Weight transformed) decomposition)
---------------------------------------------------------------------
Uranium Y (branching 234 (+) 24.6 hrs. Beta
from Uranium II) (2.2 days?)
Protoactinium 230 About 10^4 yrs. (?) Alpha
Actinium 226 20 yrs. Beta
Radio-actinium 226 19 days Alpha
Actinium X 222 (+) 11.2 days Alpha
Actinium (Emanation) 218 3.92 sec. Alpha
Actinium A 214 .002 sec. Alpha
Actinium B 210 36 min. (?) Beta, Gamma
Actinium C 210 2.16 min. (?) Alpha
Actinium D 206 4.76 min. Beta, Gamma
Actinium E (End-product 206 ............... ...............
actinium-lead)
---------------------------------------------------------------------
THORIUM SERIES
T (average Rays (given out in
Element Atomic time-period--half each
Weight transformed) decomposition)
---------------------------------------------------------------------
Thorium 232.1 2.2 × 10^{10} yrs. Alpha
Mesothorium I 228 6.7 yrs. Beta, Gamma
Mesothorium II 228 6.2 hrs. (?) Beta, Gamma
Radio-thorium 228 1.90 yrs. (?) Alpha
Thorium X 224 3.64 days Alpha
Thorium (Emanation) 220 54 sec. (?) Alpha
Thorium A 216 .14 sec. (?) Alpha
Thorium B 216 10.6 hrs. (?) Beta, Gamma
Thorium C 212 60 min. (?) Alpha
Thorium D 208 3.2 min. (?) Beta, Gamma
Thorium E (End-product 208 ............... ...............
thorium-lead)
---------------------------------------------------------------------
Transcriber’s Notes
Punctuation, hyphenation, and spelling were made consistent when a
predominant preference was found in the original book; otherwise they
were not changed.
Simple typographical errors were corrected; unbalanced quotation
marks were remedied when the change was obvious, and otherwise left
unbalanced.
This book uses terminology that was current at the time of publication,
and reflects the state of science as it was understood by the author at
that time.