Strontium compounds metal oxides

Chemical ingredients of fireworks are chosen to produce specific colors. Barium compounds produce green colors when heated, copper salts produce green and blue flames, sodium salts are yellow in flame, lithium compounds produce red colors, magnesium metal produces brilliant white fight when burned, and strontium compounds produce brilliant red colors. Salts used contain both metallic cations and nonmetallic anions. Anions such as chlorates, perchlorates, and nitrates also contribute oxidizing power to the chemical mixture. 

Recently Bednorz and Muller (1) reported possible superconductivity at 30 K in the metallic-oxide La-Ba-Cu-0 system. Subsequent work by Tanaka and co-workers (2) showed that the high temperature superconductivity is due to the solid solution La BaxCuO. y which forms in the K2NiFA-type structure. Making solid solutions with strontium instead of barium, Cava et. al. (3). were able to show bulk superconductivity at 38 K in La2 xSrxCuOA y. While solid solutions of the type La2.xMxCuOA y (M = Sr, Ba) have been known for some time, (4-5) magnetic and electron transport properties of these compounds had not previously been measured at low temperatures (i.e. <120 K). ... 

The presence of strontium and radioactive strontium compounds in the atmosphere results from both natural and anthropogenetic activities (see Section 6.2.1). Strontium is emitted into the atmosphere as strontium oxide (i. e., SrO) from emission during thermal processes. As is the case of other metallic compounds, SrO cannot be destroyed however, it can be transformed from one form to another. When SrO comes in contact with water in clouds or during washout by rain, it ionizes to form Sr+. There is no evidence for interaction of SrO with C02 (g)or other compounds in the atmosphere. 

BARIUM PERCHLORATE (13465-95-7) A strong oxidizer. Reacts violently with reducing agents, combustibles. Contact with strong acids forms explosive perchloric acid. Contact with isopropyl alcohol forms highly explosive propyl perchlorate. Contact with ammonium compounds, metal powders (especially magnesium, aluminum, sulfur, calcium hydride, and strontium hydride), or sulfur produces friction- and impact-sensitive compounds. Explodes when heated or shocked. 

There are four stable isotopes of strontium that are found naturally. In addition there are about twenty radioactive isotopes, including strontium-90, a deadly by-product of nuclear-bomb detonations. The natural forms of strontium are relatively nontoxic. Similar to calcium both physically and chemically, elemental strontium is a soft, shiny metal. Like calcium and other alkaline earth metals, it is easily oxidized and thus not found naturally in its free elemental state. Instead, it almost always is found in the + 2 oxidation state, forming such compounds as strontium oxide (SrO), strontium sulfate (SrS04, from the mineral celestite), strontium carbonate (SrCOj, from the mineral strontianite), and strontium chloride (SrC. Strontium nitrate, Sr(N03)2, is used to produce the brilliant red color seen in some fireworks and signal flares and is also used in making tracer bullets that can be seen when fired at night. Other strontium compounds are sometimes used in the manufacture of special glasses. Yet overall, strontium is not a very important element industrially or commercially, see ALSO Davy, Humphry... 

At the end of 1791 the Scottish chemist T. Hope concerned himself with studying strontianite, and established the difference between witherite and strontianite. Hope also noted that the strontium earth reacted with water more vigorously than quicklime it dissolved in water much more readily than barium oxide, and all strontium compounds turned the flame red. T. Hope proved that the new earth could not be a mixture of calcium and barium earths. Lavoisier suggested that the new earth was of metallic nature but only H. Davy succeeded in proving it in 1808. 

Other superconducting materials deposited by the sol-gel process using metal alkoxide precursors are the 1,2,4 compound YBazCu408, bismuth strontium calcium copper oxides, bismuth lead strontium calcium copper oxide, and thallium... 

For applications in heterogeneous catalysis, perovskites generally comprise a lanthanide (La is the most common) in the A site and a transition metal (Mn, Co, etc.) in the B site. The efficiency of such perovskite oxides, with or without cationic substitution, is well documented for a variety of catalytic reactions [2-9]. Actually, the specific catalytic activities of perovskites were sometimes found to be comparable to that of noble metals for various oxidation reactions. Early on, Arai et al. illustrated the activity of strontium-substituted LaMnOs, which was found to be superior to that of Pt/alumina catalysts at a conversion level below 80% [5]. Several authors have also discussed the application of La-based perovskite oxides as catalysts for volatile organic compound (VOC) oxidation (see, for example. Refs [10-14]). Zhang et al. have also shown that some perovskite oxides substituted with Pd or Cu are also good catalysts for the reduction of NO by CsHg [15-18] and by CO [19,20]. More recently, Kim et al. studied the effect of Sr substitution in LaCoOs and LaMnOs perovskites for diesel oxidation (DOC) and lean NO, trap (LNT) processes [9]. The observations made by these authors clearly indicate that the perovskites used in their study could efficiently outperform Pt-based catalysts. Typically, Lai. Sr cCoOs catalysts achieved higher... 

In general, the chemistry of inorganic lead compounds is similar to that of the alkaline-earth elements. Thus the carbonate, nitrate, and sulfate of lead are isomorphous with the corresponding compounds of calcium, barium, and strontium. In addition, many inorganic lead compounds possess two or more crystalline forms having different properties. For example, the oxides and the sulfide of bivalent lead are frequendy colored as a result of their state of crystallisation. Pure, tetragonal a-PbO is red pure, orthorhombic P PbO is yeUow and crystals of lead sulfide, PbS, have a black, metallic luster. 

Barium [7440-39-3] Ba, is a member of Group 2 (IIA) of the periodic table where it Hes between strontium and radium. Along with calcium and strontium, barium is classed as an alkaline earth metal, and is the densest of the three. Barium metal does not occur free in nature however, its compounds occur in small but widely distributed amounts in the earth s cmst, especially in igneous rocks, sandstone, and shale. The principal barium minerals are barytes [13462-86-7] (barium sulfate) and witherite [14941-39-0] (barium carbonate) which is also known as heavy spar. The latter mineral can be readily decomposed via calcination to form barium oxide [1304-28-5] BaO, which is the ore used commercially for the preparation of barium metal. 

Davy also discovered several other elements (potassium, barium, calcium, and strontium) by isolating the metals from their compounds through electrolysis. His work led to the development of electrochemistry, which is the use of electricity as the energy source to break up the oxides of these alkali and alkali earth elements. 

Strontium metal is not found in its elemental state in nature. Its salts and oxide compounds constitute only 0.025% of the Earths crust. Strontium is found in Mexico and Spain in the mineral ores of strontianite (SrCO ) and celestite (SrSO ). As these ores are treated with hydrochloric acid (HCl), they produce strontium chloride (SrCy that is then used, along with potassium chloride (KCl), to form a eutectic mixture to reduce the melting point of the SrCl, as a molten electrolyte in a graphite dish-shaped electrolysis apparatus. This process produces Sr cations collected at the cathode, where they acquire electrons to form strontium metal. At the same time, Cl anions give up electrons at the anode and are released as chlorine gas Cl T. 

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