Thorium physical properties

Properties. Pure thorium metal is a dense, bright silvery metal having a very high melting point. The metal exists in two allotropic modifications. Thorium is a reactive, soft, and ductile metal which tarnishes slowly on exposure to air (12). Having poor mechanical properties, the metal has no direct stmctural appHcations. A survey of the physical properties of thorium is summarized in Table 1. Thorium metal is diamagnetic at room temperature, but becomes superconducting below 1.3—1.4 K. 

Table 3. Physical Properties of Uranium and Thorium Carbides...

Thermal equilibrium, 56 Thermite reaction, 122 Thermometers, 56 Thiosulfate ion, 362 Third-row elements, 101 compounds, 102 physical properties, 102 properties, table, 101 Third row of the periodic table, 364 Thomson, J. J., 244 Thomson model of atom, 244 Thorium... 

As mentioned, protactinium is one of the rarest elements in existence. Although protactinium was isolated, studied, and identified in 1934, little is known about its chemical and physical properties since only a small amount of the metal was produced. Its major source is the fission by-product of uranium found in the ore pitchblende, and only about 350 milligrams can be extracted from each ton of high-grade uranium ore. Protactinium can also be produced by the submission of samples of throrium-230 (g Th) to radiation in nuclear reactors or particle accelerators, where one proton and one or more neutrons are added to each thorium atom, thus changing element 90 to element 91. 

The first actinide metals to be prepared were those of the three members of the actinide series present in nature in macro amounts, namely, thorium (Th), protactinium (Pa), and uranium (U). Until the discovery of neptunium (Np) and plutonium (Pu) and the subsequent manufacture of milligram amounts of these metals during the hectic World War II years (i.e., the early 1940s), no other actinide element was known. The demand for Pu metal for military purposes resulted in rapid development of preparative methods and considerable study of the chemical and physical properties of the other actinide metals in order to obtain basic knowledge of these unusual metallic elements. 

The very active chemical nature of calcium accounts tor its major uses. Calcium is used in tonnage quantities to improve the physical properties of steel and iron. Tonnage quantities are also used in the production of automotive and industrial hailerics. Other major uses include refining ul lead, aluminum, thorium, uranium, samarium, and oilier reactive metals. 

Table 3-2 lists important physical properties of radium and selected radium compounds. Radioactive properties of the four naturally-occurring radium isotopes are listed in Table 3-3. In addition to the naturally occurring isotopes, there are 12 other known isotopes of radium. The principal decay schemes of the uranium and thorium decay series that produce the naturally-occurring radium isotopes are presented in Figure 3-1.

Thorium is a silvery white, soft, metal, somewhat similar to lead. It can be hammered, rolled, bent, cut, shaped, and welded rather easily. Its general physical properties are somewhat similar to those of lead. It has a melting point of about 3,300°F (1,800°C) and a boiling point of about 8,100°F (4,500°C). The density of thorium is about 11.7 grams per cubic centimeter, nearly 12 times the density of water. 

The exploding wire technique was used to measure some physical properties of Th(cr) and Th(l) up to the vicinity of the thorium boiling point ca. 5000 K). The main details of the paper concern the volume expansion and electrical resistivity, which are reported as a function of enthalpy, since no temperatures were measured. This restricts their usefulness for current purposes, since the enthalpy of thorium is not known above 3400 K. However, the results did show relatively distinct breaks at the a to p and melting transformations, from which the authors deduced transition enthalpies of 3.5 and 13.9 kJ-mor in excellent agreement with existing data. 

The mode of preparation of the cellulose phosphate is of some importance. It is made by impregnating cellulose derived from wood pulp with a solution of 50 per cent urea and 18 per cent phosphoric acid, and curing in air at 130°C. The highest thorium capacity is obtained with a product cured for only a short time, but the physical properties are then unsuitable for satisfactory flow rates through a column of the material. In practice, it... 

This element therefore ought to be the last in the sequence of consecutive elements with similar properties in the first half of the sixth period, and at the place 72 an element must be expected which in its chemical and physical properties is homologous with zirconium and thorium. ... 

Large series of triscyclopentadienyl thorium, uranium, and neptunium hydrocarbyls (Op n C5H5) have been prepared since the mld-1970 s (eqs.(8), (9), and (10)). The chemical and physical properties of... 

Previous reviews of thorium nitrides are the early work in the Gmelin Handbook [13], the physical properties as tabulated by Peterson, Curtis [14], the tabulation and contributions to the thermochemical data by Rand [15], their brief mention in an engineering data tabulation of nitrides [16], and a chapter on thorium nitrides in High-Temperature Nuclear Fuel [17]. 

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