• WordNet 3.6
    • n thorium a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands
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Webster's Revised Unabridged Dictionary
    • n Thorium (Chem) A metallic element found in certain rare minerals, as thorite, pyrochlore, monazite, etc., and isolated as an infusible gray metallic powder which burns in the air and forms thoria; -- formerly called also thorinum. Symbol Th. Atomic weight 232.0.
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Century Dictionary and Cyclopedia
    • n thorium In 1900 Brauner announced his belief that, thorium, as generally known, is separable into two different elements. A little later Baskerville, working by a different method, came to the same conclusion, and in 1903 claimed to have effected its separation into three components, for two of which he proposed the new names carolinium and berzelium, retaining the name thorium for the third component. Later he found for this new or purified thorium an atomic weight of 220.1–220.6. In 1905 R. J. Meyer and A. Gumperz published the results of a careful revision of the previous work on this subject, which they found did not afford any evidence in support of the earlier claims of the separability of thorium. Thorium is a radioactive element and is the parent of a series of radioactive products of which eight separate members have already been identified. These are known as mesothorium 1, mesothorium 2, radiothorium, thorium X, thorium emanation, thorium A, thorium B, and thorium C, and are ordinarily present in thorium compounds. Thorium and its products appear to constitute a separate radioactive group or family, distinct from the uranium group, of which actinium, ionium, radium, and polonium are members, although generally found associated with it in minerals. Thorium itself emits only a-rays, but, owing to the presence of thorium disintegration-products, β- and γ-rays are also given out by thorium compounds.
    • n thorium Chemical symbol, Th; atomic weight, 231.9. The metallic base of the earth thoria, discovered by Berzelius, in 1828, in a mineral from Norway, to which the name of thorite is now given, and which consists essentially of the silicate of thorium. This earth has also been found in various other rare minerals. The metal thorium, as artificially prepared, resembles nickel in color, has a specific gravity of 7.66 to 7.8, takes fire when heated in the air, and burns with a bright flame; it dissolves readily in nitric acid, but only with difficulty in hydrochloric acid. Its chemical relations place it in the same group with tin. Also thorinum.
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Chambers's Twentieth Century Dictionary
    • n Thorium thō′ri-um a rare metal resembling aluminium, but taking fire below a red heat, and burning with great brilliancy
    • Thorium Also Thorī′num
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Webster's Revised Unabridged Dictionary
NL. See Thorite


In literature:

How much thorium, not to speak of cerium, could they take at a maximum.
"Tono Bungay" by H. G. Wells
Here thorium-X is interposed between thorium and its short-lived emanation, which decays to half its initial quantity in 54 seconds.
"Darwin and Modern Science" by A.C. Seward and Others
So, too, for the matter of that," he added in afterthought, "do thorium, and borium!
"Frenzied Fiction" by Stephen Leacock
By a somewhat similar calculation it is deduced that thorium-derived lead would possess the atomic weight of 208.
"The Birth-Time of the World and Other Scientific Essays" by J. (John) Joly
Thorium, for instance, is, as its name implies, a metal named after the thunder god Thor, to whom we dedicate one day in each week, Thursday.
"Creative Chemistry" by Edwin E. Slosson
Mantles are made by knitting cylinders of cotton or of other fiber and soaking these in a solution of the nitrates of cerium and thorium.
"Artificial Light" by M. Luckiesh
But thorium mostly gives off the kind of radiation known as alpha particles.
"Rip Foster in Ride the Gray Planet" by Harold Leland Goodwin
The only elements so far known that undergo spontaneous change are uranium and thorium.
"The Breath of Life" by John Burroughs
The density of thorium as obtained by reducing the anhydrous chloride by means of sodium was found by Chydenius, 7.657 to 7.795.
"Scientific American Supplement, No. 365, December 30, 1882" by Various
It is a typical organic compound, one of the metal radical type, and contains one atom of thorium.
"The Black Star Passes" by John W Campbell
Give the derivation of the names of the following elements: thorium, gallium, selenium, uranium.
"An Elementary Study of Chemistry" by William McPherson
Welsbach mantles consist of about 99 per cent thorium oxide and 1 per cent cerium oxide.
"The Economic Aspect of Geology" by C. K. Leith
So Grant, by this time weary in the shoulders from carrying his equipment, turned down Thorium Avenue toward Nellie's Boarding House.
"The Wealth of Echindul" by Noel Miller Loomis
But some isotopes of uranium and thorium have little beta, with some alpha and gamma, so Baxter concluded we had powdered uranium ore.
"The Blue Ghost Mystery" by Harold Leland Goodwin
Thus a metal plate or wire exposed to the action of thorium oxide for some hours became itself active.
"A Brief Account of Radio-activity" by Francis Preston Venable
Some part, however, seems to be derived from thorium, and H.A.
"Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 8" by Various
Helium is relatively abundant in many minerals, all of which are radioactive, and contain uranium or thorium as important constituents.
"Encyclopaedia Britannica, 11th Edition, Volume 13, Slice 2" by Various
Curie discovered also that pitch-blende possessed much greater radio-active power than either thorium or uranium.
"Physics" by Willis Eugene Tower
Thorium discovered by Berzelius.
"The Progress of Invention in the Nineteenth Century." by Edward W. Byrn

In news:

Thorium-based reactors could be more efficient and create less waste than today's uranium-based generating plants.
Thorium Reactors, Spinning Eggs in Milk, Cloud Computing.
Thorium reactors for nuclear energy, an experiment you can try at home, and moving to cloud computing.
Norway holds a resource of 170,000 tonnes of thorium , which amounts to 15% of the world's total of 1.2 million tonnes.
Can Using Thorium Instead of Uranium Make Nuclear Energy Safer.
Motherboard explores a common but relatively unknown nuclear fuel called thorium .
Is thorium the future of nuclear power.
In nature, thorium (such as the sample shown here) is found as thorium -232.
For the past several months, a friend of mine has been telling me about the potentially game-changing implications of an obscure (at least to me) metal named Thorium after the Norse god of thunder, Thor.
Thorium -based reactors could be more efficient and create less waste than today's uranium-based generating plants.
A large rock from an abandoned Thorium mine in central Idaho.
"There's enough Thorium here to power the United States for 500 years," Williams said.
The new research into the age of the Grand Canyon used a dating technique based on the radioactive decay of uranium and thorium atoms.
But it's in this mining camp, with its abandoned bunk houses and long-forgotten roads, that the idea of a Thorium-powered world died 40 years ago.
Smoke from a wildfire in Idaho that burned mining sites with traces of uranium and thorium contained elevated levels of radiation, but none that posed a risk to human health, state officials said on Friday.

In science:

It is interesting to examine the differential geo-neutrino signal per unit flux as a function of the energy: = σ(E ¯ν )fX (E ¯ν )/ Z dE ¯ν fX (E ¯ν ) This quantity is shown in Figs. 9 and 10 for uranium and thorium, respectively.
Geo-neutrinos and Earth's interior
Similar considerations hold for thorium and potassium, the relative mass abundance with respect to uranium being globally estimated as a(Th) : a(U) : a(K) ≈ 4 : 1 : 12000.
Geo-neutrinos and Earth's interior
It requires to determine how much uranium, thorium and potassium are on the Earth, quantities which are strictly related to the anti-neutrino luminosities from these elements.
Geo-neutrinos and Earth's interior
This holds for any value of the total uranium and thorium mass, since the precise value of ∆m2 only matters in the region near the detector.
Geo-neutrinos and Earth's interior
The results of that paper, which only considered geo-neutrinos from uranium decay chains, have been extended to include geo-neutrinos from thorium.
Geo-neutrinos and Earth's interior
In principle, this argument can be developed separately for uranium and thorium, i.e. connecting the geo-neutrino signals S (U) and S (Th) with the respective masses m(U) and m(Th) all over Earth.
Geo-neutrinos and Earth's interior
FIG. 23 Predictions on the combined signal S (U + Th) from uranium and thorium geo-neutrinos at Kamioka as a function of the radiogenic heat production rate H (U + Th).
Geo-neutrinos and Earth's interior
In 2005, the KamLAND collaboration has published (Araki et al., 2005a) experimental results, claiming some 28 geo-neutrino events from uranium and thorium decay chains in a two-year exposure.
Geo-neutrinos and Earth's interior
FIG. 30 The combined signal from uranium and thorium geo-neutrinos and the radiogenic heat production rate.
Geo-neutrinos and Earth's interior
How shall we have definite (at least 3σ) evidence of geo-neutrinos? • How much uranium and thorium are in the Earth’s crust? • How much in the mantle? • What can be said about the core? A preliminary point for establishing suitable detector locations is the reactor background.
Geo-neutrinos and Earth's interior
In this energy range, the dominant contamination comes from the progeny of the uranium and thorium chain.
Neutrino Experiments
It is claimed that this technology could increase the amount of fissile material from uranium by a factor of 60-100 and much more if the thorium breeder cycle can be realized .
The Future of Nuclear Energy: Facts and Fiction Chapter IV: Energy from Breeder Reactors and from Fusion?
Ignoring the possibility that past investigations into the thorium fuel cycle have revealed several important problems, one needs to speculate about other reasons.
The Future of Nuclear Energy: Facts and Fiction Chapter IV: Energy from Breeder Reactors and from Fusion?
The high cost of fuel fabrication, due partly to the high radioactivity of U-233 chemical ly separated from the irradiated thorium fuel.
The Future of Nuclear Energy: Facts and Fiction Chapter IV: Energy from Breeder Reactors and from Fusion?
Some concern over weapons proliferation risk of U-233 (if it could be separated on its own), although many designs such as the Radkowsky Thorium Reactor address this concern.
The Future of Nuclear Energy: Facts and Fiction Chapter IV: Energy from Breeder Reactors and from Fusion?