Scarcity

The primary reason for interest in extended Huckel today is because the method is general enough to use for all the elements in the periodic table. This is not an extremely accurate or sophisticated method however, it is still used for inorganic modeling due to the scarcity of full periodic table methods with reasonable CPU time requirements. Another current use is for computing band structures, which are extremely computation-intensive calculations. Because of this, extended Huckel is often the method of choice for band structure calculations. It is also a very convenient way to view orbital symmetry. It is known to be fairly poor at predicting molecular geometries. 

As early as 2500 bce m India indigo was used to dye cloth a deep blue The early Phoenicians discovered that a purple dye of great value Tyrian purple could be extracted from a Mediterranean sea snail The beauty of the color and its scarcity made purple the color of royalty The availability of dyestuffs underwent an abrupt change m 1856 when William Henry Perkin an 18 year old student accidentally discovered a simple way to prepare a deep purple dye which he called mauveme from extracts of coal tar This led to a search for other synthetic dyes and forged a permanent link between industry and chemical research... 

Copper acetate, ferrous acetate, silver acetate [563-63-3] basic aluminum acetate, nickel acetate [373-02-4] cobalt acetate, and other acetate salts have been reported to furnish anhydride when heated. In principle, these acetates could be obtained from low concentration acetic acid. CompHcations of soHds processing and the scarcity of knowledge about these thermolyses make industrial development of this process expensive. In the eady 1930s, Soviet investigators discovered the reaction of dinitrogen tetroxide [10544-72-6] and sodium acetate [127-09-3] to form anhydride ... 

Mixed Metal Antimony Synergists Worldwide scarcities of antimony have prompted manufacturers to develop synergists that contain less antimony. Other metals have been found to work in concert with antimony to form a synergist that is as effective as antimony alone. Thermoguard CPA from Elf Atochem NA, which contains zinc in addition to antimony, can be used instead of antimony oxide in flexible poly(vinyl chloride) (PVC) as well as some polyolefin appHcations. The Oncor and AZ products which contain siUcon, zinc, and phosphoms from Anzon Inc. can be used in a similar manner. The mixed metal synergists are 10 to 20% less expensive than antimony trioxide. 

Natural Gas Upgrading via Fischer-Tropsch. In the United States, as in other countries, scarcities from World War II revived interest in the synthesis of fuel substances. A study of the economics of Fischer synthesis led to the conclusion that the large-scale production of gasoline from natural gas offered hope for commercial utiHty. In the Hydrocol process (Hydrocarbon Research, Inc.) natural gas was treated with high purity oxygen to produce the synthesis gas which was converted in fluidized beds of kon catalysts (42). 

Radon is the heaviest of the hehum-group elements and the heaviest of the normal gaseous elements. It is strongly radioactive. The most common isotope, Rn, has a half-life of 3.825 days (49). Radon s scarcity and radioactivity have severely limited the examination of its physical properties, and the values given ki Table 3 are much more uncertain than are the values Hsted for the other elements. 

The narcotic potency and solubiUty in oHve oil of several metabohcaHy inert gases are Hsted in Table 10. The narcotic potency, ED q, is expressed as the partial pressure of the gas in breathing mixtures requited to produce a certain degree of anesthesia in 50% of the test animals. The solubiUties are expressed as Bunsen coefficients, the volume of atmospheric pressure gas dissolved by an equal volume of Hquid. The Hpid solubiHty of xenon is about the same as that of nitrous oxide, a commonly used light anesthetic, and its narcotic potency is also about the same. As an anesthetic, xenon has the virtues of reasonable potency, nonflammability, chemical inertness, and easy elimination by the body, but its scarcity and great cost preclude its wide use for this purpose (see Anesthetics). 

Despite their scarcity in nature, the tide compounds have found use in many appHcations, including pharmaceuticals, agricultural chemicals, and dyes. 

Other Resins. Some resins that were important in earlier years have decreased in commercial significance because of scarcity and increased cost of collection. They are Hsted for the historical record. 

Eatty acid soap was first used for ESBR. Its scarcity prompted the investigation of rosin acids from gum and wood as substitutes (1). The discovery of the disproportionation of rosin allowed rosin acid soaps to overcome the polymerization inhibition of untreated rosin acids. Rosin acid soaps gave the added benefit of tack to the finished polymer. In the 1990s, both fatty acid and rosin acid soaps, mainly derived from tall oil, are used in ESBR. 

Water can seldom be reused directiy. The treatment required depends on the intended second use. Disposal costs of the wastewater must be included in any economic analysis, and additional treatment for reuse may be justified when this expense is included. Costs of reclamation depend on the location, water scarcity, availabiUty of pubHc water suppHes, and the intended reuse. 

The sequence of sheets in graphite is also ABAB however, an examination of the atomic positions shows that they are not simply related to those in either kind of diamond. Thus the simple compression of graphite should not be expected to yield diamond. However, we11-crysta11i2ed graphite, in which the ABAB sequence extends for at least hundreds of layers, tends to form wurt2itic carbon. The rare rhombohedral form of graphite has an ABCABC sequence of sheets, but its scarcity has hindered its study as a source for diamond. 

Saffron is found in the pistils of the plant Crocus sativus. Saffron is often confused with safflower, sometimes known as bastard saffron. The name of the plant. Crocus sativus, comes from the Arabic word faran, meaning yellow. The Romans and the Greeks used saffron not only as a dye but also as a spice. In the early days of Greece, yellow was the official color, and Grecian women were especially fond of clothes dyed with saffron. Because of its scarcity, saffron ranked among the most expensive dyes of the ancient world. 

Since air is a mixture of predominantly nitrogen, oxygen, and a host of lesser impurities, there has been less interest in developing precise thermodynamic properties. The only recent correlation of thermodynamic properties is that published by Vasserman, et al. (Barouch, Israel Program for Scientific Translations, Jerusalem, 1970), and is based on the principle of corresponding states because of the scarcity of experimental data. 

The accuracy of QRA results is also dependent on the analysis resources. Obviously, more complete QRA models can produce more accurate results. But even the best model is worthless if the input data are speculative or erroneous. Fortunately, the scarcity of process-specific data for some applications may not be an insurmountable problem. There exist a few industrywide databases, such as those in Table 2, that... 

The limitations of the procedure were identified as (a) fixation of most design variables and (b) limited number of variables due to the scarcity of the available design and cost relationships. 

Except where otherwise stated, Ln is used rather loosely to mean most of the lanthanides the Pm compound, for instance, is usually missing simply because of the scarcity and consequent expense of Pm. 

WasserUnie, /, water line. wasser-Ios, a. waterless, without water, anhydrous, -loslich, a. water-soluble, Wasser-luftpumpe, /, water vacuum pump, -maische, /. (aqueous) infusion mash, -malerei, /, water-color painting, -mangel, m, lack (or scarcity) of water, -mantel, m. water jacket, -mass, n, water gage, -menge, /, amount of water,... 

Daly, II. E. (1974). Steady-State Economics Versus Growthmania A Critique of the Orthodox Conceptions of Growth, Wants, Scarcity, and Efficiency. Policy Science 5 149-67. 

Another characteristic of the economic-efficiency concept IS that it does not require arbitrai y decisions by the analyst about, fur example, how coal should be evaluated compared with natural gas. The question of whether I Btu of coal is equal to 1, or perhaps 1/2, Btu of natural gas is answered directly by the market. The weightings of the marketplace, revealed in relative prices, vary with scarcity, cost of production, technology, and human preferences. Decisionmakers do not need to think about the underlying reasons, however. They need to know only current prices (and make their best guesses about future prices). 

Barnett, H. J., and Morse, C. (1963). Scarcity and Growth The Economics of Natural Resource Availability. Baltimore Johns Hopkins Press for Resources for the Future. Brennan, T. J. Palmer, K. L. Koop, R. J. Ki upmck, A. J. Stagliano, V. and Burtraw, U. (1996). A Shock to the System Restructuring America s Electricity Industry. Washington, DC Resources for the Future. 

Regional scarcities of coal initially drove these uses. As petroleum became more abundant and as its price fell, oil became more attractive. In firing boilers, fuel oil possessed only a slight advantage over good-quality coal in Btus per unit volume. But liquid fuels were much easier to handle and store than coal. Competitive pressures kept the prices per Btu of residual oil and coal quite close. 

England suffers from timber and fuel wood scarcity. 

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