Alkaline earth compounds

Separation and Recovery of Rare-Earth Elements. Because rare-earth oxalates have low solubihty in acidic solutions, oxaUc acid is used for the separation and recovery of rare-earth elements (65). For the decomposition of rare-earth phosphate ores, such as mona ite and xenotime, a wet process using sulfuric acid has been widely employed. There is also a calcination process using alkaLine-earth compounds as a decomposition aid (66). In either process, rare-earth elements are recovered by the precipitation of oxalates, which are then converted to the corresponding oxides. 

The quality and yield of carbon black depends on the quaUty of the feedstock, reactor design, and input variables. The stmcture is controlled by the addition of alkaU metals to the reaction or mixing 2ones. Usual practice is to use aqueous solutions of alkaU metal salts such as potassium chloride or potassium hydroxide sprayed into the combustion chamber or added to the make oil in the oil injector. Alkaline-earth compounds such as calcium acetate that increase the specific surface area are introduced in a similar manner. 

Polymers with much higher average molecular weights, from 90,000 to 4 x 10 , are formed by a process of coordinate anionic polymerization (43—45). The patent Hterature describes numerous organometaUic compounds, aLkaline-earth compounds, and mixtures as polymerization catalysts. Iron oxides that accumulate in ethylene oxide storage vessels also catalyze polymerization. This leads to the formation of nonvolatile residue (NVR) no inhibitor has been found (46). 

In the past, there was quite a lot of confusion regarding the true nature of some alkaline-earth compounds. Several boride, nitride, and carbide compounds, as well as some mixed species, especially of calcium, were in doubt or at least subject to some ongoing discussion. For example, the phase relationships and structures of CaC2 phases I-IV were not well understood. The three nitride... 

Solid-state metathesis reactions. For a number of compounds, solid-state metathesis (exchange) reactions have the advantages of a rapid high-yield method that starts from room-temperature solids and needs little equipment. The principle behind these reactions is to use the exothermicity of formation of a salt to rapidly produce a compound. We may say that for instance a metal halide is combined with an alkali (or alkaline earth) compound of a /7-block element to produce the wanted product together with a salt which is then washed away with water or alcohol. Metathesis reactions have been used successfully in the preparation of several crystalline refractory materials such as borides, chalcogenides, nitrides. 

Potentially toxic compounds in the subsurface, such as Cd ", Pb ", or Hg ", which are generally found in very low concentrations, are considered soft cations (Buffle 1988). These ions have strong affinity to intermediate and soft ligands and therefore bond to them covalently. Borderline cations, which embrace transition metals like Cu and Ztfexhibit affinity for the soft cations as well as for alkaline-earth compounds. The order of donor atom affinity for soft metals is O < N < S. Functional groups present in subsurface organic matter that show affinity for soft and borderline metals are shown in Table 14.2. 

Alkaline earth metal oxides are generally prepared by thermal decomposition of alkaline earth compounds, such as hydroxides, chlorides, sulfates, and carbonates. 

Alkali metal ion-exchanged zeolites and occluded alkali metal oxide zeolites have been investigated extensively and applied as basic catalysts for a variety of organic transformations (1,41,221,222). Zeolites modified with alkaline earth compounds have been applied much less frequently as base catalysts for organic reactions. 

Reaction with sulfuric acid yields monoperoxysulfuric acid. Reactions with many alkaline earth compounds yield peroxides of alkaline earth metals ... 

Three methods are available for the preparation of peralkylated silyl alkaline and alkaline earth compounds. 

This work was undertaken as a part of a study of divalent lanthanide halides in an effort to obtain more accurate thermal data on EuC12 and to determine if the close similarity of the high-temperature thermodynamic properties of divalent europium and alkaline earth compounds emphasized earlier (13-16) could be extended. 

As the interest in finding alkaline-earth compounds suitable for MOCVD applications has increased, investigation of ligands that are both thermally robust and able to encapsulate large metal centers has intensified. Some of the previously discussed cyclopentadienides meet these criteria, and the related poly(pyrazolyl)borates have recently received a great deal more attention. 

A series of very volatile alkaline-earth compounds with pendent ether groups, [M(OC-/-Bu(CH2OR)2)2]2 (M = Ca, Sr, Ba R = i-Pr or Et), have been synthesized by the halide metathesis and metal/ammonia methods as well as by reaction between the metal amides M(N(SiMe3)2)2(THF) and the alcohols HOC-t-Bu(CH2OR)2.48 Alcoholysis of metal amides has... 

The original interest in these systems stems from the need to selectively extract heavy alkaline-earth metals from various media.276-280 A number of alkaline-earth compounds with polydentate ligands and anionic ligands... 

The present research therefore has two aims, the first to show that paper alkalized with a sodium compound—sodium carbonate—behaves in the presence of a transition metal catalyst in the manner indicated by the literature. The second aim is to learn to what extent the behavior of paper alkalized with the alkaline earth compounds differs from this. 

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