Formation of elemental

The sulfur then reacts to form the polysulfide according to equation 12. The key is the use of a catalyst to promote the formation of elemental sulfur. Commercial systems are based on the use of air with an activated carbon catalyst (41). The need for additional sulfur is eliminated, but the sulfur level is... 

For many waste streams, electrical efficiencies are compromised owing to the corrosivity of the solution toward the precipitated metals and/or the low concentrations of metals that must be removed. The presence of chloride in the solution is particularly troublesome because of the formation of elemental chlorine at the anode. Several commercial cells have become available that attempt to address certain of these problems (19). 

However, as HOX is consumed, hydrolysis is retarded because of build-up of free amine. Consumption of hypohalous acid through reaction with HX can result in formation of elemental halogen HOX + + X X2 + H2 O (1—3). The tendency for halogen formation is much greater for HOBr and... 

In this thesis we suggest a model of the formation of elements, which allows us to make the connection between the spread of elements and their nuclear char ge. We ve got a function of distribution for the state close to the final period of active formation of elements and for the state, corresponding to the period of forming of condensed bodies [2, 3]. 

The reaction appears 10 proceed first by the formation of elemental sulfur which then equilibrates with more HSO3" to form the product ... 

Work at Berkeley-Livermore in 1974 first convincingly demonstrated the synthesis of this element via the reaction " Cf( 0,4n) 106. Contemporaneous work at Dubna applied their novel cold fusion method (p. 1280) to reactions such as 82 Pb - - 24 Cr although this methodolgy was crucial to the synthesis of all later elements (107-112) it did not at that time demonstrate the formation of element 106 with adequate conviction. Very recently, element 106 was resynthesized by a new group at Berkeley using exactly the same reaction as employed in 1974. The isotope 106 decays with a half-life of 0.8 0.2 s to 104 and then by a second... 

Vapor pressures of phases in these systems were measured by the Knudsen effusion technique. Use of mass spectrometer-target collection apparatus to perform thermodynamic studies is discussed. The prominent sublimation reactions for these phases below 2000 K was shown to involve formation of elemental plutonium vapor. Thermodynamic properties determined in this study were correlated with corresponding values obtained from theoretical predictions and from previous measurements on analogous intermetallics. 

STRATEGY The reaction is endothermic and, because a gas is produced from solid reactants, occurs with an increase in entropy. Because AHc > 0 and AS° > 0, the formation of products from pure reactants becomes spontaneous at temperatures for which AH° TAS°. The temperature at which the tendency for the reaction to occur begins solves to T = AH7AS°. We use data from Appendix 2A (and remember that the standard enthalpies of formation of elements are zero). 

Nucleosynthesis is the formation of elements. Hydrogen and helium were produced in the Big Bang all other elements are descended from these two, as a result of nuclear reactions taking place either in stars or in space. Some elements—among them technetium and promethium—are found in only trace amounts on Earth. Although these elements were made in stars, their short lifetimes did not allow them to survive long enough to contribute to the formation of our planet. However, nuclides that are too unstable to be found on Earth can be made by artificial techniques, and scientists have added about 2200 different nuclides to the 300 or so that occur naturally. 

Dehydrocoupling A General Strategy for the Formation of Element-Element... 

In addition to the mainstream of element formation, several nontraditional technological approaches were carried out for the formation of elements with nanometer sizes and their utilization for construction of single-electron elements (WiUdns et al. 1989, Shonen-berger et al. 1992a, Dorogi et al. 1995, Erokhin et al. 1995a). 

The value of this method lies in the fact that formation of elemental selenium is unlikely to occur since the high-valency species such as Se(IV) that could oxidize the selenide ions are absent from solution. The SeSO and SOj ions (or their protonated forms) do not oxidize Se , while any free Se that may be formed would redissolve in sulfite giving selenosulfate again, since the latter is prepared by dissolving Se in excess sulfite. 

Sulfide minerals can also be oxidized by the acidic ferric sulfate solutions produced (as shown in the last two equations), with the formation of elemental sulfur ... 

Gauvin, Franjois, Harrod, John F., and Woo, Flee Gweon, Catalytic Dehydrocoupling A General Strategy for the Formation of Element—Element Bonds. .. 42 363... 

Instantaneous recycling cannot be used to describe the formation of elements, such as iron, to which there is a significant contribution from stars that take a non-negligible time to complete their evolution. This case can still be handled within the framework of analytical models by a delayed production approximation (Pagel 1989a), which works by the simple device of assuming that the delayed element or component thereof starts to be released at a single time A after the onset of star... 

Fuerstenau (1980) found that sulphide minerals are naturally floatable in the absence of oxygen. Yoon (1981) ever attributed the natural floatability of some sulphide minerals to their very low solubility. Finkelstein et al. (1975) considered that the natural floatability of sulphide minerals are due to the formation of elemental sulphur and related to the thickness of formation of elemental sulphur at the surface. Some authors reported that the hydrophobic entity in collectorless flotation of sulphide minerals were the metal-deficient poly sulphide (Buckley et al., 1985). No matter whichever mechanism, investigators increasingly concluded that most sulphide minerals are not naturally floatable and floated only under some suitable redox environment. Some authors considered that the natural floatability of sulphide minerals was restricted to some special sulphide minerals such as molybdenite, stibnite, orpiment etc. owing to the effects of crystal structure and the collectorless floatability of most sulphide minerals could be classified into self-induced and sulphur-induced floatability (Trahar, 1984 Heyes and Trahar, 1984 Hayes et al., 1987 Wang et al., 1991b, c Hu et al, 2000). 

The reaction potential producing elemental sulphur are 0.24 V at pH = 6 based on the reaction (2-10), 0.28 V at pH =8 on the reaction (2-11), and 0.1 V at pH = 11 on die reaction (2-12) with lO" mol/L concentration of dissolved species. The reported flotation initial potential (see Table 2.1) are very close to these theoretical calculation values. The theoretical and experimental values in Table 2.1 indicate that the elemental sulphur might be responsible for the hydrophobicity of sulphide surfaces. At different pH media the formation of elemental sulphur occurs and hence the flotation behavior undergoes different processes. 

Figure 2.24 shows the voltammograms of pyrite electrode in neutral media. It follows that the potential range of flotation relates to reactions (2-24) and (2-25). The potential calculated in reaction (2-24) is 161- 180 mV, pyrite exhibit collectorless floatability due to the formation of elemental sulphur. 

Selenium, in the form of selenate or selenite, is toxic to D. desulfuricans (Tomei et al. 1995) and Wolinella succinogenes (Tomei et al. 1992) at elevated levels. At sublethal levels of 0.1-1. OmM selenite or 10 mM selenate, minimal levels of growth is observed with both D. desulfuricans and Wolinella succinogenes. With both selenate and selenite, colloidal elemental selenium (Se°) is produced inside the cell and released into the culture fluid after cell death. This reduction of Se(VI) and Se(IV) by these anaerobes is not coupled to growth and proceeds by mechanisms that have not yet been identified. Selenite and selenate reduction with formation of elemental selenium by these nonrespiratory processes serve to detoxify the environment for future bacteria and may be important for the geochemical cycle of selenium. 

Table 10.5 Heats of combustion (heats of formation) of elements used in pyrolants and of their combustion products [NASA SP-273].

A similar reaction with the formation of elemental hydrogen was observed when dimethylaminoalane (Me2NAlH2)3 was treated with 1,1-dimethylhydr-azine [Eq. (10)] [26]. All dimethylamino substituents were replaced by terminal hydrazido groups (24 66% yield). Dianionic hydrazido ligands analogous to compound 23 were formed. They occupy bridging positions... 

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