Surface chemical properties sulfur

The corrosion behavior of tantalum is weU-documented (46). Technically, the excellent corrosion resistance of the metal reflects the chemical properties of the thermal oxide always present on the surface of the metal. This very adherent oxide layer makes tantalum one of the most corrosion-resistant metals to many chemicals at temperatures below 150°C. Tantalum is not attacked by most mineral acids, including aqua regia, perchloric acid, nitric acid, and concentrated sulfuric acid below 175°C. Tantalum is inert to most organic compounds organic acids, alcohols, ketones, esters, and phenols do not attack tantalum. 

J. A. Rodriguez, The chemical properties of bimetallic surfaces importance of ensemble and electronic effects in the adsorption of sulfur and S02, Prog. Surf. Sci., 2006, 81, 141. 

Most chemical properties of technetium are similar to those of rhenium. The metal exhibits several oxidation states, the most stable being the hep-tavalent, Tc +. The metal forms two oxides the black dioxide Tc02 and the heptoxide TC2O7. At ambient temperature in the presence of moisture, a thin layer of dioxide, Tc02, covers the metal surface. The metal burns in fluorine to form two fluorides, the penta- and hexafluorides, TcFs and TcFe. Binary compounds also are obtained with other nonmetaUic elements. It combines with sulfur and carbon at high temperatures forming technetium disulfide and carbide, TcS2 and TcC, respectively. 

Sulfur dioxide is a colorless, water-soluble irritant gas (Costa and Amdur 1996). It can be detected by taste at concentrations of 0.35-1.05 ppm (parts per million) and has an immediate pungent irritating odor at a concentration of 3.5 ppm (WHO 1984). It has been termed a mild irritant (Amdur 1969). Ambient sulfur dioxide can react with oxygen to form sulfur trioxide, which then reacts with water (on moist surfaces) to produce sulfuric acid. Sulfur dioxide also can react with water to form sulfurous acid, which dissociates to sulfite and bisulfite ions. The chemical and physical properties of sulfur dioxide are presented in Table 9-1. 

TJ apid entrainment carbonization of powdered coal under pressure in a partial hydrogen atmosphere was investigated as a means of producing low sulfur char for use as a power plant fuel. Specific objectives of the research were to determine if an acceptable product could be made and to establish the relationship between yields and chemical properties of the char, with special emphasis on type and amount of sulfur compound in the product. The experiments were conducted with a 4-inch diameter by 18-inch high carbonizer according to a composite factorial design (1, 2). Results of the experiments are expressed by empirical mathematical models and are illustrated by the application of response surface analysis. 

In the case of sulfur-mustard, the situation is somewhat more complex. It is marginally soluble in water tending to form droplets, and hydrolysis occurs at the droplet surface. This property has made measuring the hydrolysis rate constant difficult, and half-lives anywhere from 2 to 30 hours are reported. Chemically, the hydrolysis of HD involves the sequential replacement of the chlorine atoms by hydroxyl groups through cyclic sulfonium ion intermediates to form thiodiglycol (TDG), Reaction (2). If a median... 

The presence of sulfur either as an impurity adsorbed on the surface or as a minor alloying addition to a multicomponent material, induces changes in the chemical composition of the surface leading to subsequent modifications in the crystallographic and electronic structures such modifications ware known to affect dramatically many physico-chemical properties. 

Nam et al.l studied the deactivation of a commercial catalyst, 10% V2O5 on alumina, by SO2 in the reduction of NO by NH3. The feed gas was the flue gas from the combustion of No.2 fuel oil in a laboratory furnace, doped with NO and NH3. The physico-chemical properties of the deactivating catalysts were correlated with its activity and accumulating sulfur content, and the deactivation was modeled. The activation energies of fresh and deactivated catalysts were similar. The sulfur content of the catalyst, as well as the surface area, appeared to be a dominant deactivation parameter, analogous to coke-induced deactivation. Pore size distribution changes indicated that... 

When petroleum or kerosene (as the raw materials for gas oil or lubricants) are purified by using oleum or sulfuric acid, a reaction with the aromatic compounds takes place. While these substances were originally seen as waste products, later their chemical structures and surface-active properties were identified, thus leading to special applications for such products. Nowadays, petroleum fractions with a high content of aromatic hydrocarbons are treated with sulfur trioxide to form alkylaryl sulfonates. These products are then transformed into the sodium, ammonium or alkaline-earth salts. They are soluble in oils and therefore are of some importance as additives in lubricants, oil fuels and corrosion-inhibiting oils. Further more, they are also used as auxiliaries in production of fabrics and as dispersants in enhanced oil recovery processes. 

The chemical properties span a range similar to the representative elements in the first few rows of the periodic table. Francium and radium are certainly characteristic of alkah and alkaline earth elements. Both Fr and Ra have only one oxidation state in chemical comhina-tions and have little tendency to form complexes. Thallium in the 1+ oxidation state has alkah-like properties, but it does form complexes and has extensive chemistry in its 3+ state. Similarly, lead can have alkaline earth characteristics, hut differs from Ra in forming complexes and having a second, 4+, oxidation state. Bismuth and actinium form 3+ ions in solution and are similar to the lanthanides and heavy (Z > 94) actinides. Thorium also has a relatively simple chemistry, with similarities to zirconium and hafiuum. Protactinium is famous for difficult solution chemistry it tends to hydrolyze and deposit on surfaces unless stabilized (e.g., by > 6 M sulfuric acid). The chemistry of uranium as the uranyl ion is fairly simple, hut... 

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