SrCOs

Raw ] Ia.teria.ls. Most of the raw materials are oxides (PbO, Ti02, Zr02) or carbonates (BaCO, SrCO, CaCO ). The levels of certain impurities and particle size are specified by the chemical suppHer. However, particle size and degree of aggregation are more difficult to specify. Because reactivity depends on particle size and the perfection of the crystals comprising the particles, the more detailed the specification, the more expensive the material. Thus raw materials are usually selected to meet appHcation-dependent requirements. 

Since there are no volatile components this halophosphate phosphor is prepared with close to the stoichiometric amounts of SrHPO, SrCO, CaCO, BaCO, SrCl2, or NH Cl and EU2O2. The blend is fired under an atmosphere containing 1—2% hydrogen at 1100°C. A small excess of chloride provides some fluxing action and gives weU-formed crystals of apatite. The chlorapatites are dimorphous one modification is hexagonal and the other monoclinic. 

Strontium has a valence of +2 and forms compounds that resemble the compounds of the other alkaline-earth metals (see Barium compounds Calcium compounds). Although many strontium compounds are known, there are only a few that have commercial importance and, of these, strontium carbonate [1633-05-2] SrCO, and strontium nitrate [10042-76-9], Sr(N03)2, are made in the largest quantities. The mineral celestite [7759-02-6], SrSO, is the raw material from which the carbonate or the nitrate is made. 

Strontium Carbonate. Strontium carbonate, SrCO, occurs naturally as strontianite in orthorhombic crystals and as isomorphs with aragonite, CaCO, and witherite, BaCO. There are deposits in the United States in Schoharie County, New York in WestphaUa, Germany and smaller deposits in many other areas. None is economically workable. Strontianite has a specific gravity of 3.7, a Mohs hardness of 3.5, and it is colorless, gray, or reddish in color. 

Strontium Hexaferrite. Strontium hexaferrite [12023-91 -5] SrO-6 Fe2 03, is made by combining powdered ferric oxide, Fe203, and strontium carbonate, SrCO, and calcining the mixture at ca 1000°C in a rotary kiln (9). The material is cmshed, mixed with a binder, and pressed or extmded into... 

Aluminum or sodium amalgam reduces 3-ones to 1,2-dihydro derivatives (71TH21500), as does borohydride (63JCS5156) and catalytic hydrogenation (Pd/SrCOs) (71TH21500). Catalytic (Pd/C) reduction of a 5-one also gave a 1,2-dihydro compound (74JMC553). 

Experiments show that 0.0059 gram of SrCOs will dissolve in 1.0 liter of water at 25°C. What is K,p for SrCOj ... 

The principal minerals of Sr are strontionitc (SrCO,) and celesite (SrS04) those of Ba are barite (BaS04) and witherite (BaCO,). Strontionitc and barite are the usual sources of metallic Sr and Ba, respectively. Traces of both elements occur in nearly all limestones and dolomites and small amounts are usually present in natural limes. Furthermore, although neither element occurs as an independent silicate, traces of each may replace part of the Ca, Pb or K in compounds containing one or more of these elements. 

Starting materials are obtained from the ores SrO is readily prepared from SrCO the principal ore, by calcination, and SrCU is obtained by thermal decomposition, in an HCl atmosphere, of SrClj 6 H O, the produet of the dissolution of SrCO, in aq HCl. Conversion of BaS04, the major source of Ba, into BaO is effected via BaS and BaCO,. Thus BaS04 is reduced to BaS by heating with carbon in a rotary kiln BaCO is precipitated when BaS is dissolved in water and treated with COj production of BaO is achieved by heating an intimate mixture of BaCO, and earbon. 

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. 

Strontium carbonate (SrCO ) is used to make radiation-resistant glass and TV picture tubes, as well as pyrotechnics. 

Though the detailed mechanism of the action of SrC03 on AP propellants has yet to be fully understood, the results of the thermograms indicate that the site and mode of the action of SrCOj are in the condensed phase rather than in the gas phase. The decomposition process of AP particles is substantially altered by the addition of SrCO,. 

The two principal strontium minerals are its carbonate, strontianite, SrCOs, and the more abundant sulfate mineral celestite, SrS04. 

Elemental composition Sr 59.35%, C 8.14%, 0 32.51%. SrCOs is dissolved in dilute acid and carbon dioxide liberated is identified by the lime-water test (turns lime water milky). Strontium in solution is analyzed by various methods mentioned earlier (See Strontium). 

Carbonates Aragonite CaCOs, calcite CaCOs, cerussite PbCOs, magnesite MgCOs, strontianite SrCOs, witherite BaCOs... 

T0146 Catalytic Combnstion Corporation, SRCO and HD-SRCO... 

The SRCO catalytic combustion unit treats volatile organic compound (VOC) laden process exhaust air. SRCO stands for self-recuperative catalytic oxidizer. The SRCO can be furnished as a complete operating vacuum extraction and catalytic oxidation system or as a stand-alone catalytic oxidizer to interface with an existing vacuum extraction and/or air stripper system. HD-SRCO stands for halogenated destruction self-recuperative catalytic oxidizer. This system is basically the same as the SRCO system, except that it remediates halogenated hydrocarbons using a different catalyst. 

Many of the high Tc ceramic superconductors can be prepared by similar solid state techniques. In the Bi-Sr-Ca-Cu-O system Bi2Os, SrCOs, CaCOs or Ca(OH)2, and CuO are often used... 

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