Thorium radio

At the time of the discovery of radio-activity, about seventy-five substances were called elements in other words, about seventy-five different substances were known to chemists, none of which had been separated into unlike parts, none of which had been made by the coalescence of unlike substances. Compounds of only two of these substances, uranium and thorium, are radio-active. Radio-activity is a very remarkable phenomenon. So far as we know at present, radio-activity is not a property of the substances which form almost the whole of the rocks, the waters, and the atmosphere of the earth it is not a property of the materials which constitute living organisms. It is a property of some thirty substances—of course, the number may be increased—a few of which are found widely distributed in rocks and waters, but none of which is found anywhere except in extraordinarily minute quantity. Radium is the most abundant of these substances but only a very few grains of radium chloride can be obtained from a couple of tons of pitchblende. 

R. B. Owens, Macdonald professor of electrical engineering at McGill University, and Sir Ernest Rutherford noticed that when a thorium compound is placed in an open vessel exposed to air currents, its radio-... 

Since other projectiles, such as neutrons, protons, and deuterons, have also been used to produce artificial radioactivity, the number of active elements thus created already exceeds by far the number of naturally occurring radio-elements (129, 130, 131). By January, 1940, three hundred and thirty artificial radioactivities had been described these include isotopes of every known element in the range of atomic numbers 1 to 85 inclusive, as well as isotopes of thorium (atomic number 90) and of uranium (atomic number 92) (132). Thus the work of M. and Mme. Joliot-Curie opened up vast avenues of research on the physical, chemical, and radioactive properties of these isotopes and on their therapeutic uses. In 1935 they were awarded the Nobel Prize in chemistry (133). 

Rutherford was awarded a scholarship to be a research student at the University of Cambridge and began research under J.J. Thomson. He soon abandoned research on his radio wave detector to work on the power of X-rays to confer electric charge on gases but soon turned to researching the problem of the rays emitted by thonum. Rutherford found three kinds of radiation, which he named alpha, beta, and gamma. In collaboration with Frederick Soddy, he was able to isolate a substance, thorium X, and identify the phenomenon of radioactive half-life and formulated an explanation of radioactivity. Rutherford was awarded the 1908 Nobel Prize for chemistry for his work in radioactivity. 

Excluding most of the radio-elements derived from thorium and uranium. 

A more convincing experiment performed by Crookes [34] involved Fe(OH)3 as a carrier of uranium X (having the more convenient ti/2 = 24 days) precipitated from the soluble uranyl carbonato complex in excess (NH4)2C03. These observations show an insoluble hydroxide, but they did not establish the thorium(IV) chemistry of this Th isotope, the first descendant of Sir Ernest Rutherford (1871-1937) and Frederick Soddy (1877-1956) then showed [35] that ti 2 = 3.6 days of thorium X ( Ra), soluble in aqueous ammonia, is replaced by radio-elements precipitating as hydroxides. In 1907 Rutherford demonstrated [36] that ionium ( °Th with tj j = 80000 years, the immediate ancestor of Ra with t j = 1600 years in uranium minerals), Th (tiy2 = 14100 million years), and radiothorium Th (ti/2 = 1-9 years) cannot be separated by chemical means. 

The number given for radio-active processes has been calculated by assuming that the kinetic energy of the helium atoms emitted, which is of the same order, e.g. for RaC, RtzF, Actin-B, Thorium-B and -C is equal to hv. There is no means of guessing the effect of temperature on the... 

Radio- nuclide Half-life PWR Uranium (3.3% U) HTGR U, thorium, and recycled uranium LMFBR Uranium and recycled plutonium... 

Elyahyaoui, A., Brillard, L., Boulhassa, S., Hussonnois, M., Guillaumont, R., Complexes of thorium with phosphoric acid, Radio-chim. Acta, 49, (1990), 39-44. Cited on pages 326, 327, 330, 604. 

Another common method of dating U-minerals is by considering its content of lead isotopes. Lead has four stable isotopes of which three are end products of radioactive decay series. The fourth lead isotope, Pb, is foimd in lead minerals in about 1.4% isotopic abundance and has no radio-genetic origin. At the time of formation of the earth, all the Pb in nature must have been mixed with unknown amounts of the other lead isotopes. If a lead-containing mineral lacks Pb, it can be assumed that presence of the other lead isotopes together with uranium and/or thorium must be due to their formation in the decay... 

Ruben S, Kamen M, Hassid WZ (1940) Photosynthesis with radioactive carbon II, Chemical properties of the intermediates. J Am Chem Soc 62 3443 Rutherford E (1900) A radio-active substance emitted from thorium compotmds. Phil Mag 49 1 Rutherford E (1906) The mass and velocity of the a particles expelled from radium and actinium. Phil Mag 12 348... 

Another strand of development came from several attempts to separate some of these new radio-elements chemically, which ended in failure. First of all, in 1907 Herbert McCoy and WiUiam Ross concluded that, in the case of thorium and radiothorium, Our experiments strongly indicate that radiothorium is entirely inseparable from thorium by chemical processes, " a comment Soddy considered the first definitive statement of the chemical inseparability of what were soon to be called isotopes. Soddy himself wrote in the same year that there seemed to be no known method of separating thorium X from mesothorium.They were in fact two isotopes of thorium. Similar cases began to multiply. Bertram Boltwood discovered the radio-element ionium, which could not be chemically separated from thorium. In another famous case, Hevesy and Paneth were asked by Rutherford to try to separate radio-lead from ordinary lead and likewise failed to do so, in spite of using 20 different chemical methods. Their work was not entirely in vain, however, since it led to the development of the use of radioactive tracers, which have become an indispensable tool in modem chemistry and biochemistry. 

In addition to the normal radioactivity of radium, thorium, polonium, and uranium, radioactivity may be induced in these elements. The cyclotron has made it possible to obtain high-energy particles in considerable concentrations, and so it may be anticipated that artificial radio elements will become increasingly accessible to research workers. It is for this reason... 

Rutherford, E. A radio-active substance emitted from thorium compounds. Philos. Mag. 49, 1-14 (1900)... 

The initial event that led to the development of radio-metric dating methods was the discovery, by Wilhelm Roentgen in 1895, of X-rays, which are produced when a beam of electrons strikes a solid target. It was thought that the emission of X-rays might be related to the phosphorescence produced by cathode rays on the walls of a vacuum tube. In 1896 Henri Becqueral, while studying phosphorescence, discovered that uranium salts emitted radiation that had properties similar to X-rays. Two years later Marie and Pierre Curie discovered that thorium also emitted radiation, and they named the new phenomenon... 

---