Preparation and purification of metals

The preparation and purification of metal halides for hlgh-temperature spectroscopy present certain difficulties which vary for the different salts. All chemicals used In the present work were "anhydrous salts purchased from Cerac/Pure Inc. AICI3,... 

The methods of preparation and purification of metal derivatives of 1,3-diketones have been described in a previous volume. Because of the interest in the structure " and reactions of metal derivatives of /3-keto imines, RC0CH2C(=NR )R", it is desirable to consider the methods of preparation of these compounds. Inasmuch as /3-keto imines are closely related to 1,3-diketones and to salicylaldimines, o-HOC6H4CH==NR, the methods of preparation show similarities. Although this review is concerned principally with /3-keto imines, some comparisons with 1,3-diketones and salicylaldimines are made. 

Sodium Tetrahydroborate, Na[BH ]. This air-stable white powder, commonly referred to as sodium borohydride, is the most widely commercialized boron hydride material. It is used in a variety of industrial processes including bleaching of paper pulp and clays, preparation and purification of organic chemicals and pharmaceuticals, textile dye reduction, recovery of valuable metals, wastewater treatment, and production of dithionite compounds. Sodium borohydride is produced in the United States by Morton International, Inc., the Alfa Division of Johnson Matthey, Inc., and Covan Limited, with Morton International supplying about 75% of market. More than six million pounds of this material suppHed as powder, pellets, and aqueous solution, were produced in 1990. 

As a result of their reactivity, particular attention must be given to preparation and purification of the metals, the conditions under which the metals, alloys and compounds are handled and the choice of material for the containment vessel. Ultrapure group-IIB metals may be used without further purification, but it is advisable to purify the group-IIA metals by a multidistillation process, the final distillation preferably being carried out in situ. The reactants and products are best handled in an atmosphere of a purified inert gas, usually He or Ar (N2 cannot be used because of the ready formation of group-IIA metal nitrides) alternatively, they can be handled under vacuum or, in rare cases, under halide fluxes. The containment vessel is normally fabricated from a refractory. 

Gschneidner Jr., K.A. (1980) Preparation and purification of rare earth metals and effect of impurities on their properties. In Science and Technology of Rare Earth Materials, eds. Subbarao, E.C. and Wallace, W.E. (Academic Press, New York), p. 25. 

Sodium hydride and potassium hydride can also be used to prepare enolates from ketones. The reactivity of the metal hydrides is somewhat dependent on the means of preparation and purification of the hydride.5... 

The book on the Investigation of Perfection treats of the preparation and purification of substances or reagents which are useful for the perfecting of the metals, and the work is expressly intended to be an introduction to the main work, the Summa. It is confined to directions for purifying salt, alkali, sal ammoniac, alums, copperas, and similar salts, and to obtaining the metals in the form of solutions. These directions are invariably perfectly clear, consistent and practical, for example ... 

The most popular of his treatises in the fifteenth century and later was probably his Thesaurus Thesaurorum et Rosarium Philosophorum (Treasure of Treasures and Rose Garden of the Philosophers). It consists of two parts, the first in ten brief chapters gives the conventional Greek-Arabian doctrine of the origin and constitution of metals, of sulphur, mercury, and the philosopher s stone, and transmutation. The second part of thirty-two chapters contains seemingly specific directions for operations for the preparation and purification of substances supposed to be necessary for the preparation of the elixirs and the philosopher s stone. As Professor Thomas Thomson pertinently remarks,18... 

White [7] gives a general review that includes information about the preparation and purification of a variety of alkali and alkaline earth halide melts. Information about fluorides can also be found in an earlier review article by Bamberger [8]. Many different halide melts have been used as solvents for electrochemistry, and a complete discussion of all of these melts is outside the scope of this chapter. However, two systems that have generated continuous interest over the years are the LiCl-KC1 eutectic (58.8-41.2 mol%, mp = 352°C) [9] and the LiF-NaF-KF (46.5-11.5-42.0 mol%, mp = 454°C) also known as FLINAK [10]. The former is an electrolyte commonly used in thermal batteries, whereas the latter molten salt is of interest for refractory metal plating. 

The preparation and properties of the dithiocarboxylic acids and their metal complexes have been reviewed several times.38"11 The formation of C—C bonds in the direct reaction of CS2 requires sufficiently nucleophilic carbon bases, directly or potentially accessible in the form of ambifunction-al phenoxides, organometalfic compounds, CH acidic compounds, enamines or ketimines. Carba-nions react with CS2 to give dithiocarboxylates. The preparation and purification of the adds is performed via their salts. Metal complexes are in general readily available. The bonding in these complexes is mostly of the type (27) but a bonding mode (28) is also found. Action of elemental sulfur upon heavy metal complexes of (29) aromatic dithiocarboxylic acids yields the perthio complexes (29) of these compounds. 

Preparation and Purification of Actinidine Metals J. C. Spirlet, J. R. Peterson, and L. B. Asprey... 

The structures, types, properties, uses, nomenclature, and general methods of preparation of metal derivatives of 1,3-diketones have been discussed in a previous volume.1 It now seems desirable to consider in somewhat more detail the various factors involved in the preparation and purification of these substances. 

Chemistry began to emerge as a science in the early seventeenth century. Its roots included practical chemistry (the mining and purification of metals, the creation of jewelry, pottery, and weaponry), medicinal chemistry (the use of herbs and various preparations made from them), and mystical beliefs (the search for the Philosopher s Stone or the Universal Elixir). 

Typically the desired isocyanide substitution products are obtained in good yield from such reactions. However, a major drawback of this strategy entails the prior preparation and purification of the labile precursor complexes. The transition metal catalyzed substitution of the metal hexacarbonyls [M(CO)e] (M = Cr, Mo, W) by isocyanides has, by way of contrast, proved to be a direct and rapid synthetic route that reliably gives the products [M(C0)6, (CNR)J (n = 1-3) in high yield. We describe here general procedures that illustrate the methods involved and that highlight the synthetic utility of these reactions. 

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