Metallic calcium, preparation

Gadolinium is found in several other minerals, including monazite and bastnasite, both of which are commercially important. With the development of ion-exchange and solvent extraction techniques, the availability and prices of gadolinium and the other rare-earth metals have greatly improved. The metal can be prepared by the reduction of the anhydrous fluoride with metallic calcium. 

Titanium Silicides. The titanium—silicon system includes Ti Si, Ti Si, TiSi, and TiSi (154). Physical properties are summarized in Table 18. Direct synthesis by heating the elements in vacuo or in a protective atmosphere is possible. In the latter case, it is convenient to use titanium hydride instead of titanium metal. Other preparative methods include high temperature electrolysis of molten salt baths containing titanium dioxide and alkalifluorosiUcate (155) reaction of TiCl, SiCl, and H2 at ca 1150°C, using appropriate reactant quantities for both TiSi and TiSi2 (156) and, for Ti Si, reaction between titanium dioxide and calcium siUcide at ca 1200°C, followed by dissolution of excess lime and calcium siUcate in acetic acid. 

Plutonium metal is prepared by two methods--direct reduction of the oxide by calcium (DOR)U,2J, and reduction of PuF by calcium in our metal preparation line (MPL)(3) (see Figure 1). In the DOR process, the plutonium contenF of the reduction slag is so low that the slag can be sent to retrievable storage without further processing. Metal buttons that are produced are no purer than the oxide feed and/or the calcium chloride salt. Los Alamos purifies the buttons by electrorefin-ing(4i,5 ), yielding metal rings that are > 99.96 percent plutonium. 

Controlled metal complexation — While uncontrolled metal complex -ation can be a major source of problems, controlled complexation is a potentially useful selectivity modifier. The key is to evaluate the effects of only one metal at a time, which in turn requires that your sample be stripped of metals in preparation for your experimental treatment. The EDTA-imidazole treatment described above can be used for this purpose. For evaluating the effects of ferric iron or calcium, buffer exchange the treated sample into 0.05 M MES, pH 6, then add the metal salt of choice to a concentration of 5 mM. For other metals, buffer exchange the treated sample into 0.05 M Tris, pH 8, then add the metal salt of choice to 5 mM. 

Bulk holmium metal is prepared by reduction of holmium chloride or fluoride by sodium, calcium, or magnesium in a tantalum crucible under argon atmosphere ... 

Vanadium metal is prepared from pentoxide, V2O5, by reduction with calcium at elevated temperatures. Presence of iodine lowers calcium reduction temperature to 425°C because of heat of formation of calcium iodide. Pentoxide also may be converted to the trichloride, VCI3, and the trichloride reduced with magnesium metal or magnesium-sodium mixture at high temperatures to form high purity ductile metal. Alternatively, a fused mixture of vanadium chloride, sodium chloride, and hthium chloride may be electrolyzed to produce the metal in high purity. 

Preparation of Calcium Carbide by Reacting Metallic Calcium with Carbon. Prepare a mixture from 5 g of calcium (crumbles) and 3 g of powdered coal. Put the mixture in a crucible, close it with... 

How can the oxides, peroxides, and hydroxides of the alkaline-earth metals be prepared What are the commercial names of calcium and barium hydroxide solutions How do the solubility, basic properties, and thermal stability of the hydroxides change in the series calcium-strontium-barium ... 

The discovery of acetylene in 1836(or 1837) is attributed to Edmond Davy, but it was not until I860 that Berthelot definitely identified and named it(Ref 9, p 101 Ref 16, p 469). The compd obtained by Berthelot from cuprous acetylide was not pure because it contained some vinyl chloride. Acetylene was not produced commercially until Ca carbide was produced in the lab in 1899 by Morehead Willson, by heating a mixt of lime and coke in an electric furnace. They expected to prepare metallic calcium... 

Table I lists the results of this experiment. A metallic calcium sample was prepared from limestone from an 11-m depth and was not preenriched. The sample was assumed to contain no cosmogenic 41Ca at the instrumental detection limit of the AMS system used, because of its geological age (Mesozoic) and burial depth. No counts were observed for a time approximately three times longer than that for the bone sample. From the measurement...

A reaction mixture was prepared that contained a metal at concentrations in excess of that of ATP. The reaction was started by the addition of the enzyme, and samples were taken and analyzed by the HPLC method. Surprisingly, the chromatograms for the experiments that included metals were different from the ones obtained earlier. In the original experiments, only two peaks were present, those representing ATP and AMP. However, in the experiment that included the metal calcium, the chromatograms showed the elution of an additional peak jsut after the ATP emerged (Fig. A.5B). Further studies showed that the new peak had a retention time identical to that of ADP, and therefore we assumed that this second peak was ADP. From these findings, we speculated that the metal had stimulated the activity of an enzyme that catalyzed the formation of ADP. 

The potassium salt is the most soluble, whilst the caesium salt is quite insoluble in water. Both the rubidium and the caesium salts may be prepared by double decomposition of dilute solutions of their chlorides with the nitroso salts of sodium or potassium. The thallium salt may be prepared in a similar manner by means of thallium sulphate. The nitroso salts of the alkaline earth metals—calcium, barium, and magnesium—are very soluble in water. 

Calcium also reacts with water, with less vigoi. The reaction of metallic calcium with cold water provides a simple and safe way of preparing hydrogen in the laboratory. The equation for this reaction is... 

Reduction of Chromic Chloride, CrClj.—Wohler obtained metallic chromium by reduction of chromic chloride with potassium, while Fremy obtained the metal in a crystalline condition by passing sodium vapour over chromic chloride in an atmosphere of pure dry hydrogen. Wohler prepared similar crystals—minute octahedra— by fusion of chromic chloride with zinc under a layer of mixed sodium and potassium cHorides, and removal of the zinc from the alloy so formed by means of nitric acid. Metallic calcium reduces chromic chloride at a dull red heat without formation of an alloy. ... 

Plutonium metal is prepared by calcium reduction of plutonium fluorides or oxides in induction-heated MgO crucibles, under an inert atmosphere of helium or argon. The thermodynamics of plutonium reduction are discussed later in this chapter. 

Metallic calcium is prepared industrially this way, as are several other active metals as well as the halogens CI2 and Bt2. 

Interest in the synthesis, structural characterisation and preparative uses of less common metalloorganophosphide systems has also continued. A review of recent developments in the organic chemistry of calcium includes coverage of calcium organophosphides which, in view of their reactivity (and the ease of handling of metallic calcium), may have some promise as... 

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