Alkaline-earth metals decomposition temperatures

Uranium can be prepared by reducing uranium halides with alkali or alkaline earth metals or by reducing uranium oxides by calcium, aluminum, or carbon at high temperatures. The metal can also be produced by electrolysis of KUF5 or UF4, dissolved in a molten mixture of CaCl2 and NaCl. High-purity uranium can be prepared by the thermal decomposition of uranium halides on a hot filament. 

Alkaline earth metal alkoxides decompose to carbonates, olefins, hydrogen, and methane calcium alkoxides give ketones (65). For aluminum alkoxides, thermal stability decreases as follows primary > secondary > tertiary the respective decomposition temperatures are ca 320°C, 250°C, and 140°C. Decomposition products are ethers, alcohols, and olefins. 

Salt-inclusion solids described herein were synthesized at high temperature (>500°C) in the presence of reactive alkali and alkaline-earth metal halide salt media. For single crystal growth, an extra amount of molten salt is used, typically 3 5 times by weight of oxides. The reaction mixtures were placed in a carbon-coated silica ampoule, which was then sealed under vacuum. The reaction temperature was typically set at 100-150 °C above the melting point of employed salt. As shown in the schematic drawing in Fig. 16.2, the corresponding metal oxides were first dissolved conceivably via decomposition because of cor-... 

The auxiliary electrolyte is generally an alkali metal or an alkaline earth metal halide or a mixture of these. Such halides have high decomposition potentials, relatively low vapor pressures at the operating bath temperatures, good electrolytic conductivities, and high solubilities for metal salts, or in other words, for the functional component of the electrolyte that acts as the source of the metal in the electrolytic process. Between the alkali metal halides and the alkaline earth metal halides, the former are preferred because the latter are difficult to obtain in a pure anhydrous state. In situations where a metal oxide is used as the functional electrolyte, fluorides are preferable as auxiliary electrolytes because they have high solubilities for oxide compounds. The physical properties of some of the salts used as electrolytes are given in Table 6.17. 

Decomposition Temperatures of the Carbonates of Alkaline-Earth Metals... 

When arsine is passed over a heated metal, such as the alkali and alkaline earth metals, zinc or tin, the decomposition of the gas is accelerated and the arsenide of the metal is formed. If platinum is used, the removal of arsenic from the gas is complete.3 The action of sodium or potassium on arsine in liquid ammonia yields 4 the dihydrogen arsenide (MHgAs). Heated alkali hydroxides in the solid form quickly decompose the gas, forming arsenites, and at higher temperatures arsenates and arsenides of the metals.5 The aqueous and alcoholic solutions have no appreciable action.6 When the gas is passed over heated calcium oxide the amount of decomposition is not more than that due to the action of heat alone. Heated barium oxide, however, is converted into a dark brown mixture of barium arsenite and arsenate, hydrogen being liberated.7 The gas is absorbed by soda-lime.8... 

Maleic anhydride decomposes exothermically, evolving carbon dioxide, in the presence of alkali- or alkaline earth- metal or ammonium ions, dimethylamine, triethylamine, pyridine or quinoline, at temperatures above 150°C [1]. Sodium ions and pyridine are particularly effective, even at concentrations below 0.1%, and decomposition is rapid [2]. An industrial incident involved gas-rupture of a large... 

Sulphates of the alkali- and alkaline-earth metals are stable at all temperatures lower than that of the electric arc but all other sulphates decompose, the primary product being the oxide of the metal and sulphuric anhydride the latter, however, being unstable at a red-heat, decomposes partly into sulphur dioxide and free oxygen. This decomposition is made use of in the preparation of Nordhausen sulphuric acid, a fuming liquid, consisting chiefly of H2S207 it is made by distilling partially dried ferrous sulphate from fireclay retorts 2 Fe S 04 = Fe2 Oa + S 02 + S 03 the... 

Co. surface area = 300 m2/g ) with aqueous solutions of Cu, Cr, Mg, Ca, Sr, and Ba in Nitrate. All the catalysts have Cu to Si02 weight ratio of 14/86. For promoted catalyst, the Cr to Cu molar ratio was varied from 1/4 0 to 1/4, and the alkaline earth metal to Cu molar ratio was kept at 1/10. The impregnated catalysts were dried at 100 °C overnight, calcined at 450 for 3 h and then reduced in a stream of 10% H2 in Ar at 300 °C for 2 h. The copper surface areas of catalysts were determined by the N20 decomposition method described elsewhere [4-5J. The basic properties of the catalysts were determined by temperature-programmed desorption ( TPD ) of adsorbed carbon dioxide. Ethanol was used as reactant for dehydrogenation reaction which was performed in a microreactor at 300°C and 1 atm. 

The salts of poly(methacrylic acid) with Na, Li, K and Cs (CAS for Na salt 25086-62-8) decompose at approximately 350°, whereas the Mg and other alkaline earth metal salts decompose at 500°. The NH4 salt decomposes somewhat differently with elimination of NH3, H2O, and other fragments, at higher temperatures (500° C) forming some isocyanic acid and HCN [119], Some results on poly(methacrylic acid) thermal decomposition as reported in literature are given in Table 6.7.18 [6]. 

The formation of alkali-metal and alkaline-earth-metal sulphides and polysulphides from the elements in liquid ammonia has been extensively studied in the past, but the reactions between the metals and hydrogen sulphide in liquid ammonia have drawn detailed attention only recently. It has been suggested that the equilibrium of H2S in this solvent to give the solvated hydrosulphide ion accounts for the formation of KSH even with an excess of metal. With the alkaline-earth metals, effective preparative methods have been developed for the sulphides from H2S in liquid ammonia but anhydrous hydrosulphides have not been obtained. Now, hydrosulphides have been prepared of the form M(SH)2,xNH3 (M = Ca, Sr, or Ba x — 4, 6, or 0, respectively) from the metals with H2S in ammonia, but the compounds are stable only at low temperatures. Those of Ca and Sr are stable at —45 °C but decompose to the monosulphides at room temperature. Ba(HS)2 decomposes to BaS at 100 °C with evolution of a mole of H2S. For M (SH) (M = Rb or Cs), thermal decomposition gives polysulphides. The hydrosulphides of Rb, Cs, Sr, and Ba hydrolyse rapidly in moist air.74... 

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