FINELY DIVIDED METALS

Thorium metal alloys readily with a large number of metals, including Fe, Co, Ni, Cu, Au, Ag, B, Pt, Mo, W, Ta, Zn, Bi, Pb, Hg, Na, Be, Mg, Si, Se, and Al. Like many electropositive metals, finely divided thorium metal is pyrophoric in air, and bums to give the oxide. Massive metal, chips, and turnings... 

There are three main types of pyrophoric agents white phosphorus and other inorganic non metals, finely divided metals, and certain organometallic compds... 

Alkali metals, finely divided aluminum and magnesium particles, hydrazine, diborane, metal hydrides, and hydrogen are strong reducing agents [35]. An example of a significant problem is the possible explosive reaction between light metals and carbon tetrachloride which is itself a stable compound [57]. 

A number of substances react vigorously with water, sometimes with the formation of hydrogen gas, which itself may ignite in the presence of air. Examples or such reactants are alkali metals, finely divided light metals and their hydrides, anhydrous metal oxides, anhydrous metal halides, nonmetal halides, and nonmetal oxides as well as certain organics such as anhydrides... 

Of the coinage metals, finely divided copper shows evidence of strong rehybridization of adsorbed ethyne, such as occurs with transition metals Ni, Pd, Pt, and Rh, which have unfilled d orbitals. On the other hand, SER spectra from ethyne on cold-deposited silver at low temperatures show only moderately perturbed 7T-bonded species. There is SERS evidence of polymerization to long-chain polyenes on silver and gold electrodes at room temperature. 

Because hafnium has a high absorption cross-section for thermal neutrons (almost 600 times that of zirconium), has excellent mechanical properties, and is extremely corrosion resistant, it is used to make the control rods of nuclear reactors. It is also applied in vacuum lines as a getter —a material that combines with and removes trace gases from vacuum tubes. Hafnium has been used as an alloying agent for iron, titanium, niobium, and other metals. Finely divided hafnium is pyrophoric and can ignite spontaneously in air. 

Equations (II) to (IX) illustrate basic methods of preparation, but many variations are used, particularly in industry, to obtain an economic yield. Phthalic acid, phthalamide, phthalimide, and phthalic anhydride, together with urea, are often used instead of phthalonitrile, and catalysts such as ammonium molybdate or zirconium tetrachloride may be employed (249, 251, 269). The reaction between phthalonitrile and metals (finely divided or acid-etched) is usually very vigorous at 250°-300°C, sufficient heat being generated to maintain the reaction temperature. This is an illustration of the ease with which the phthalocyanine skeleton is formed. Even more surprising are the observations that palladium black (118) and gold (189) will dissolve in molten phthalonitrile. Reaction (III) between phthalonitrile and a finely divided metal, metal hydride, oxide, or chloride is perhaps the most generally employed. For the unstable phthalocyanine complexes such as that of silver (11), the double decomposition reaction... 

ANTIMONY TRICHLORIDE (10025-91-9) Cl3Sb Contact with moist air forms corrosive hydrogen chloride fumes. Contact with water, steam forms hydrochloric acid and toxic antimony oxychloride. Aqueous solution is an acid. Violent reaction with ammonia, strong bases, amines, amides, and inorganic hydroxides alkali metals finely divided aluminum potassium, sodium. Attacks metals, releasing flammable... 

To form copper(II) azide from copper metal, finely divided copper is left in contact with dilute hydrazoic azid (2%) for approximately two months. After a few days, white Cu(I) azide begins to appear as an intermediate. The presence of oxygen or other oxidants (e.g., hydrogen peroxide) is essential to obtain Cu(II) azide quantitatively as black-violet microcyrstals [62,181,183]. 

Tungsten and compounds Few reports of human toxicity. Some saits may reiease aoid upon contaot with moisture. Chronic exposure to tungsten carbide cobait amaigams in the hard-metais industry may be associated with fibrotic iung disease. See cobait. 5 mg/m (insoluble compounds) 1 mg/m (soluble compounds) Elemental tungsten is a gray, hard, brittle metal. Finely divided powders are flammable. 

Uranium compounds Many salts are irritating to the respiratory tract soluble salts are potent kidney toxins. Uranium is a weakly radioactive element (alpha emitter) decays to the radionuclide, thorium 230. Uranium has the potential to cause radiation injury to the lungs, tracheobronchial lymph nodes, bone marrow, and skin. 0.2 mg/m (soluble and Insoluble compounds, as U), A1 tOrng/m Dense, silvery-white, lustrous metal. Finely divided powders are pyrophoric. Radioactive. 

Every oxidation must be accompanied by a reduction (i.e., the electrons must have somewhere to go). So it is impossible to determine experimentally the potential of any rfwg/e electrode. We therefore establish an arbitrary standard. The conventional reference electrode is the standard hydrogen electrode (SHE). This electrode contains a piece of metal electro-lytically coated with a grainy black surface of inert platinum metal (finely divided metals such as Pt often appear black), immersed in a 1 solution. Hydrogen, H2, is bubbled... 

The reaction between phthalonitrile and metals (finely divided or acid etched) is usually very vigorous at 250-300°C and sufficient heat is generated to maintain the reaction temperature. These compounds are monofianctional with respect to the formation of phthalocyanine rings [42,56-58]. The cyclo-tetramer-ization of four phthalonitrile molecules into a phthalocyanine macrocycle involves a reduction reaction which requires two electrons in addition to the 16 Ti-electrons from the 8 nitrile groups to yield the 18 7r-electron aromatic system. For metallophthalocyanine the two extra electrons are provided by metal or metal salts. The use of reducing coreactants such as 1,2,3,6-tetrahydropyridine or hydroquinone is effective for the conversion of phthalonitrile to phthalocyanine. The reactions are normally carried out under pressure. Bis-... 

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