Polysulfides powders

Batsanov et al. 23) reacted sulfur with PtCU and PtBr2 by heating mixtures of the reactants in evacuated, sealed ampoules. At 100 -200°C after 12-24 h, sulfide chlorides PtCljS (1.70 < x < 2 0.6 s y < 3.35) and sulfide bromides PtBr S (1.87 < x 2.06 0.84 y s 1.80) were formed. The compositions depended on the initial PtX2 S ratio, and the temperature. At 320-350°C, loss of chlorine led to the compounds PtClS (1.7 y 1.9). According to their X-ray powder patterns, all of these products retained the main structural features of the original platinum halides. From considerations of molar volumes, the authors deduced the presence of polysulfide anions. 

Many of the polysulfides described above have been investigated by X-ray diffraction on either powders or single crystals. In all cases the more sulfur-rich anions (n>3) form unbranched chains the symmetry of which varies between Ci, C2, and Cs. According to Fig. 1 the symmetry C2 results if all torsion angles have the same sign (right-handed helix + + +... left-handed helix ----...). If the different torsion angles of the anion vary between + and... 

Some compounds with network structures are synthesized by high-temperature reactions of metals with elemental sulfur [2, 8]. Rauchfuss et al. exploited the low-temperature synthesis of metal polysulfides by the reaction of metals with elemental sulfur in strong donor solvents. The reaction of copper powder with Ss in pyridine gives a copper polysulfide cluster Cu4(S5)2(-py)4 as orange crystals (Scheme 10) [45]. Furthermore, zinc powder reacts... 

The above-mentioned method is useful but metals that form strong M-S bonds (e.g., Hg, Ag, Sn) do not dissolve in W-Melm solutions of sulfur. This problem has been solved by the addition of Mg to the reaction mixture. Metal polysulfides having a variety of metals can be synthesized by the 7 T-Melm/ M-i-Mg/Sg method (Scheme 11) [48]. For example, a mixture of Mg, Sb powder (1 eq.), Sg (15 eq. as S) and W-Melm is heated at 80 °C for 48 h to afford the orange powder of [Mg(N-MeIm)5]Sb2Sj ( x 15) in 88% yield. Rauchfuss et al. proposed the mechanism of these reactions as follows. First, the reduction of Sg with Mg occurs to give the [Mg(W-MeIm)6] salt of Sg , which is probably in equilibrium with Sg, Ss ", Ss" and other species. Independently, the sulfuration of the thiophilic metal takes place. Next, the polysulfide an-... 

Early tests [37] utilized a cell design similar to that of early MCFC experiments. The assembled cell, machined from graphite blocks, is shown as Fig. 24. The electrodes and current collectors were machined from graphite and dense carbon, respectively. The electrolyte was a mixture of 63% Na2S, 37% Li2S, believed to melt near 850 °C the melting point after several days of operation was below 700 °C, probably because of polysulfide formation. The electrolyte was immobilized in a matrix of MgO, the whole formed by hot-pressing a mixture of electrolyte and ceramic powders. 

Barium Peroxide. The commercial product is a dull yellow powder containing about 90% Ba02 and about 8.5% active oxygen. The principal use is in pyrotechnics, but there are also small uses in the curing of polysulfide rubbers and in the production of certain titanium-aluminum alloys. 

High-brisance crystalline explosives, such as RDX or octogen, can be embedded in curable or polyadditive plastics such as polysulfides, polybutadiene, acrylic acid, polyurethane, etc. The mixture is then cured into the desired shape. Other components such as aluminum powder can also be incorporated. The products obtained can be of any desired size, and specified mechanical properties can be imparted to them, including rubber-like elasticity (-> LX and -> PBX). They can also be shaped into foils. 

The hydrogen polysulfides are yellow liquids, which from the tetra-sulfide upwards have no definite freezing points. They are labile with respect to change into sulfur and hydrogen sulfide, and decompose on contact with powdered quartz and glass, wood, or paper, or traces of basic substances the same applies to hydrogen disulfide. 

In addition to use of organic chemicals, mbbers can be devulcanized by means of inorganic compounds. Discarded tires and tire factory waste were devulcanized by desulfurization of suspended mbber vulcanizate cmmb (typically 10 30 mesh) in a solvent such as toluene, naphtha, benzene, or cyclohexane in the presence of sodium (Myers et al., 1997). The alkali metal cleaves mono-, di-, and polysulfidic crosslinks of the swollen and suspended vulcanized mbber crumb at around 300°C in the absence of oxygen. However, this process may not be economical because the process involves swelling of the vulcanized mbber crumb in an organic solvent where the metallic sodium in molten condition should reach the sulfidic crosslink sites in the mbber cmmb. Also, solvent may cause pollution and be hazardous. A technology was also proposed to reclaim powder mbbers using an iron oxide phenyl hydrazine based catalyst (Kawabata et al., 1981) and copper(I) chloride-tributylamine catalyst (Kawabata et al., 1979). 

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