Mantles, Gas

Cerium is a component of misch metal, which is extensively used in the manufacture of pyrophoric alloys for cigarette lighters. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. The oxide is an important constituent of incandescent gas mantles and is emerging as a hydrocarbon catalyst in self cleaning ovens. In this application it can be incorporated into oven walls to prevent the collection of cooking residues. 

Gas-liquid mixing Gassliquid transfer Gas mantles Gas, manufactured... 

The minerals on which the work was performed during the nineteenth century were indeed rare, and the materials isolated were of no interest outside the laboratory. By 1891, however, the Austrian chemist C. A. von Welsbach had perfected the thoria gas mantle to improve the low luminosity of the coal-gas flames then used for lighting. Woven cotton or artificial silk of the required shape was soaked in an aqueous solution of the nitrates of appropriate metals and the fibre then burned off and the nitrates converted to oxides. A mixture of 99% ThOz and 1% CeOz was used and has not since been bettered. CeOz catalyses the combustion of the gas and apparently, because of the poor thermal conductivity of the ThOz, particles of CeOz become hotter and so brighter than would otherwise be possible. The commercial success of the gas mantle was immense and produced a worldwide search for thorium. Its major ore is monazite, which rarely contains more than 12% ThOz but about 45% LnzOz. Not only did the search reveal that thorium, and hence the lanthanides, are more plentiful than had previously been thought, but the extraction of the thorium produced large amounts of lanthanides for which there was at first little use. 

The uses of Th are at present limited and only a few hundred tonnes are produced annually, about half of this still being devoted to the production of gas mantles (p. 1228). In view of its availability as a by-product of lanthanide and uranium production, output could be increased easily if it were to be used on a large scale as a nuclear fuel (see below). 

Gas-liquid volumetric mass transfer coefficient correlations, for airlift reactors, 15 704-705t Gas lubrication, 15 252 Gas mantles cerium in, 5 689 thorium in, 24 757 Gas masks, 5 832-835 Gas meter provers, liquid displacement, 11 652... 

The concentrations of thorium in both hard and soft tissues of humans have been determined by a few authors. The concentration of thorium-232 in the blood of normal populations (not occupationally or otherwise known to be exposed to levels higher than background level of thorium) in the United Kingdom was 2.42 pg/L. The thorium-232 level in the urine of the same population was below the detection limit of 0.001 pg/L, although the concentration in the urine of exposed workers ranged from less than 0.001-2.24 pg/L. The highest value (2.24 pg/L) was found in a worker in the thorium nitrate gas mantle industry (Bulman 1976 Clifton et al. 1971). 

Cerium(lll) chloride is used to prepare cerium metal and other cerium salts. It also is used as a catalyst in olefin polymerization, and in incandescent gas mantles. 

Thorium nitrate is a reagent for measuring fluorine and for making thori-ated tungsten filaments. Thorium nitrate containing 1% cerium nitrate is the impregnating liquid in making incandescent gas mantles. 

The oxide is used in phosphors that form red color in color television tubes. Also, it is used in gas mantles and acetylene hghts. Other uses are in yttrium-iron garnets for microwave filters in lasers, and as a stabdizer for high temperature in refractories. 

Origins. Since the 1890 S, monazite, the first commercial rare earth ore, was mined from black beach sands in Brazil and shipped to Austria for its 5 to 10% thorium oxide content. Carl Freiherr Auer von Welsbach spent 20 years of research work developing a bright incandescent gas mantle he discovered in 1866 with... 

Baron Auer is best remembered for his invention of the incandescent gas mantle, a truly great advance in the history of illumination (55). Instead of attempting to produce a gas which would bum with a luminous flame, he decided to use a non-luminous flame to heat a refractory mantle to incandescence. The problem, as he said, "was not to find a process by which an infusible compound could be given a definite shape. This invention is founded, above all, on the fact, proved by numerous experi-... 

Baron Auer von Welsbach, 1858-1929. Austrian chemist and chemical technologist. Discoverer of praseodymium and neodymium. Inventor of the Welsbach gas mantle, the osmium filament electric lamp, and the automatic gas lighter. 

Current NRC regulations for source material in 10 CFR Part 40 (AEC, 1961) and byproduct material in 10 CFR Part 30 (AEC, 1965a) specify conditions for exemption of many products or materials that contain small amounts of radioactive material (see also Schneider et al, 2001). These exemptions apply to commercial or specialized industrial uses of radioactive materials, as well as their disposal, and they include many common consumer products e.g., timepieces, smoke detectors, thorium gas mantles). These exemptions were established based on judgments by AEC and NRC that the benefits of exempt uses far outweighed the risks to public health. 

Th02, is a white solid that adopts the fluorite structure (as do the MO2 phases of the other actinides). When heated it gives off a rather bluish light if about 1% cerium is added, the light is both whiter and more intense so that the mixture came to be used in making incandescent gas mantles, widely used for lighting until comparatively recently. 

The metals themselves are very electropositive, and are accordingly difficult to prepare. Electrolytic reduction of a fused oxide-fluoride mixture may be used. An alloy containing about 70% cerium and smaller amounts of other rare-earth metals and iron is highly pyrophoric that is, it gives sparks when scratched. This alloy, called Mischmetal, is widely used for cigarette lighters and gas lighters. The use of a mixture of cerium dioxide and thorium dioxide in gas mantles has been mentioned under thorium. 

Titanium, rutile, ilmenite, titanium dioxide, titanium tetrachloride. Zirconium, zircon- Hafnium. Thorium, thorite, monazite sand, the Welsbach gas mantle. 

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