Oxysalt

Silberoxyd, n. silver oxide, -ammoniak, n, fulminating silver, -salz, n. silver oxysalt. 

Decomposition of the rare earth nitrates proceeded [821] through the intermediate formation of oxysalts of the form MON03 and E values were low Nd(N03)3, 33 kJ mole 1, 663-703 K Dy(N03)3, 23 kJ mole 1, 583—633 K Yb(N03)3, 46 kJ mole 1, 563—598 K. Thermogravimetric curves showed that the formation of anhydrous salts was possible, in contrast to observations by Wendlandt and Bear [826]. In a similar study [827] of the reaction of Pr(N03)3 at 558—758 K, the intermediate formation of a nitrite is postulated during decomposition to a non-stoichiometric residual oxide, Pr0li83 (the actual composition depends on temperature). 

The Lewis definition covers all AB cements, including the metal oxide/metal oxysalt systems, because the theory recognizes bare cations as aprotic acids. It is also particularly appropriate to the chelate cements, where it is more natural to regard the product of the reaction as a coordination complex rather than a salt. Its disadvantages are that the definition is really too broad and that despite this it accommodates protonic acids only with difficulty. 

Oxysalt bonded cements are formed by acid-base reactions between a metal oxide in powdered solid form and aqueous solutions of metal chloride or sulphate. These reactions typically give rise to non-homo-geneous materials containing a number of phases, some of which are crystalline and have been well-characterized by the technique of X-ray diffraction. The structures of the components of these cements and the phase relationships which exist between them are complex. However, as will be described in the succeeding parts of this chapter, in many cases there is enough knowledge about these cements to enable their properties and limitations to be generally understood. 

The three major types of oxysalt bonded AB cement are the zinc oxychloride, the magnesium chloride and the magnesium oxysulphate cements. The bases employed, therefore, are either zinc oxide or magnesium oxide, both of which readily undergo hydration in aqueous solution, behaving as M(OH)2 species and acting as a source of hydroxyl ions. They are thus both clearly bases in the Bronsted-Lowry sense. 

By contrast, the acidity of the metal salts used in these cements has a less clear origin. All of the salts dissolve quite readily in water and give rise to free ions, of which the metal ions are acids in the Lewis sense. These ions form donor-acceptor complexes with a variety of other molecules, including water, so that the species which exists in aqueous solution is a well-characterized hexaquo ion, either Mg(OH2)g or Zn(OH2)g. However, zinc chloride at least has a ternary rather than binary relationship with water and quite readily forms mixtures of Zn0-HCl-H20 (Sorrell, 1977). Hence it is quite probable that in aqueous solution the metal salts involved in forming oxysalt cements dissolve to generate a certain amount of mineral acid, which means that these aqueous solutions function as acids in the Bronsted-Lowry sense. 

These cements were the earliest of the oxysalt bonded cements to be prepared (Sorel, 1855) and their chemistry has been the subject of numerous investigations over the years. There are considerable difficulties associated with such investigations. Not only does the cement contain a complex mixture of different crystalline precipitates but it is unaffected by boiling water and dissolves only slowly in strong acids. Consequently separation or analysis of any of the phases which may be present is difficult. Nonetheless, as early as 1925 at least 17 crystalline compounds were claimed to occur in the zinc oxychloride cement (Mellor, 1925). 

DAMPS) combined with oxysalts of vanadium, niobium, tantalum or titanium, zirconium, hafnium ... 

The actual composition present in the Br2/BrF3 mixture is not known, and any fluorination reaction may be a composite reaction of BrF, BrF3 and BrF5. It is not necessary to assume that BrFa is the reactive constituent, although this is probable. Consider the fluorination of a species X—a metal, oxide, oxysalt, halide, etc.—to the fluoride XF by a mixture of bromine fluorides BrFgj. The general reaction is... 

Earthquakes provide the ultimate test of the storage of incompatible chemicals and are sometimes followed by fires in chemical stores. Very few causes of ignition are found alkali metals halogen oxysalts in conjunction with strong acids and sulphuric or nitric acid and cellulose (wood flooring). These usually then ignite vapours of flammable solvents. 

Natural fibrous materials are identified somewhat by chance. For example, there are seven vanadate and seven vanadium oxysalt minerals on the list of fibrous minerals. These species are composed of a rare element, vanadium, but the fibrous samples may have attracted attention because they are often brightly colored. Vanadinite [Pb5(V04)3Cl] for example, is bright orange-red. Further, the list of natural mineral fibers we have compiled contains seventy-seven phosphate species. So many phosphates are listed because detailed descriptions of these mostly quite rare minerals were readily available (Nriagu and Moore, 1984). 

Bismuth is stable to both dry and moist air at ordinary temperatures. At elevated temperatures, the vapors of the metal combine rapidly with oxygen, forming bismuth trioxide, Bi203. The element dissolves in concentrated nitric acid forming bismuth nitrate pentahydrate, Bi(N03)3 5H20. Addition of water to this salt solution precipitates an oxysalt, Bi203N205 2H20. Reaction with hydrochloric acid followed by evaporation of the solution produces bismuth trichloride, BiCB. 

Addition of water precipitates out an oxysalt, Bi203N205 H20. The degree of hydrolysis and the product composition can vary with the amount of water and the reaction temperature... 

Atomic and ionic radii affect the attraction, for electrons and anions, and govern such properties as basicity. Basicity differences affect in the hydrolysis of ions, the solubilities of salts, the thermal decomposition of oxysalts and the formation of complex species. 

The tetrahedral Cu04 group is rarely observed and no strong evidence has ever been presented for this highly symmetrical environment about the divalent copper ion. Coordinations higher than VI (or IV + II) are also very rare. Statistical data for Cu2+ coordination environments in 234 oxysalts and 75 minerals will be summarized. 

Oxysalts are divided into normal, aoid, and hasie. 

Teesb oomponnds oorre ond to the metallic oxysalts of the acids. 

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