Fluorides of metals

There are also potentially important inorganic applications of COF. Most of the industrially important low-oxidation-state metal fluorides are prepared from the reaction of their oxides, hydroxides or carbonates with aqueous or anhydrous HF. However, preparation of fluorides of metals in high formal oxidation states is usually achieved by the use of elemental fluorine on the metal, because of the problem of hydrolysis from the reversible reaction of the oxide with HF ... 

The diversity of radical processes accompanying ECF suggests there is little discrepancy, if any, with interactions of organic compounds with fluorides of metals with variable valences. However, this is not always so. 

Davidovich, R.L. (1976) The Atlas of Derivathogrammes of Complex Fluorides of Metals III-IV Groups, Science, Moscow (in Russian). 

There are many other reactions of relevance to the preparation of fluorides. Some occur at high pressures. Some involve decomposition reactions (of hydrates or fluorides). Reduction reactions with metals, with CO, PF3 and other reagents as well as with thermal treattnent are used to prepare fluorides of metals in lower oxidation states (EuFj EuF, MoF M0F3, etc.). 

A patent [21] describes the fluorination of substances containing N-H bonds. Substances such as alkali metal amides, urea, biuret, hydrazine, and others were reported to react with elemental fluorine in the presence of fluorides of metals which form acid salts with HF. These salts, e. g., NaF or LiF, act as catalysts under the conditions used. Good yields of NF3 as well as of N2F2 and N2F4 were obtained when the external temperature of the reactor was maintained between 0 and 100°C. 

Using Super-Acids as Catalysts. Super-acid catalysts can directly condense CH4 into CJ hydrocarbons at relatively mild temperatures. The work in this area were mainly carried out by Olah and his co-workers (see review by Kuo (1987)). The super-acids are generally higher valency Lewis acid fluorides of metals of Groups IV, V and VI of the periodic table which were used at 50-200 C and 1 to >150 atm. Research in this area is exploratory. Also, handling of strong acids can be quite expensive. No thermochemical calculations were carried out because its reaction products were not sufficiently defined. 

The change of friction coefficient is mainly affected by two factors. One of the factors is phase construction of fluorides. The fluoride of metal is product of ionic bound of fluoride and metal. Therefore, the fluorides of metal have some special phase construction. For example, fluorides calcium CaFj), it is a non-layer micro-structure, but its phase construction has a slip plane (Ca atomic... 

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. 

Perchloric acid (HCIO4 Ho —13.0), fluorosulfuric acid (HSO3F Ho — 15.1), and trifluoromethanesulfonic acid (CF3SO3H Ho —14.1) are considered to be superacids, as is truly anhydrous hydrogen fluoride. Complexing with Lewis acidic metal fluorides of higher valence, such as antimony, tantalum, or niobium pentafluoride, greatly enhances the acidity of all these acids. 

Compounds containing fluorine and chlorine are also donors to BF3. Aqueous fluoroboric acid and the tetrafluoroborates of metals, nonmetals, and organic radicals represent a large class of compounds in which the fluoride ion is coordinating with trifluoroborane. Representative examples of these compounds are given in Table 5. Coordination compounds of boron trifluoride with the chlorides of sodium, aluminum, iron, copper, 2inc, tin, and lead have been indicated (53) they are probably chlorotrifluoroborates. 

CoF is used for the replacement of hydrogen with fluorine in halocarbons (5) for fluorination of xylylalkanes, used in vapor-phase soldering fluxes (6) formation of dibutyl decalins (7) fluorination of alkynes (8) synthesis of unsaturated or partially fluorinated compounds (9—11) and conversion of aromatic compounds to perfluorocycHc compounds (see Fluorine compounds, organic). CoF rarely causes polymerization of hydrocarbons. CoF is also used for the conversion of metal oxides to higher valency metal fluorides, eg, in the assay of uranium ore (12). It is also used in the manufacture of nitrogen fluoride, NF, from ammonia (13). 

Table 3. Solubility of Metal Fluorides in Anhydrous Hydrogen Flnoride ...

Magnesium fluoride is a by-product of the manufacture of metallic beryllium and uranium. The beryllium or uranium fluorides are intimately mixed with magnesium metal in magnesium fluoride-lined cmcibles. On heating, a Thermite-type reaction takes place to yield the desired metal and Mgp2 (13). Part of the magnesium fluoride produced in this reaction is then used as a lining for the cmcibles used in the process. 

Use of excess sodium drives the reaction, usually done under an argon or helium blanket, to completion. After cooling, the excess sodium is leached with alcohol and the sodium and potassium fluorides are extracted with water, leaving a mass of metal powder. The metal powder is leached with hydrochloric acid to remove iron contamination from the cmcible. 

Putile Ceramic Pigments. StmcturaHy, aH mtile pigments are derived from the most stable titanium dioxide stmcture, ie, mtile. The crystal stmcture of mtile is very common for AX2-type compounds such as the oxides of four valent metals, eg, Ti, V, Nb, Mo, W, Mn, Ru, Ge, Sn, Pb, and Te as weH as haHdes of divalent elements, eg, fluorides of Mg, Mn, Fe, Co, Ni, and Zn. 

In the production of metallic uranium the fluoride UF4 is used for magnesium reduction since die reduction of UCI4 does not produce sufficient heat. The chloride can be reduced with calcium, when a signihcantly greater amount of heat is generated to reach die desired temperature. 

A number of attempts to produce tire refractory metals, such as titanium and zirconium, by molten chloride electrolysis have not met widr success with two exceptions. The electrolysis of caesium salts such as Cs2ZrCl6 and CsTaCle, and of the fluorides Na2ZrF6 and NaTaFg have produced satisfactoty products on the laboratory scale (Flengas and Pint, 1969) but other systems have produced merely metallic dusts aird dendritic deposits. These observations suggest tlrat, as in tire case of metal deposition from aqueous electrolytes, e.g. Ag from Ag(CN)/ instead of from AgNOj, tire formation of stable metal complexes in tire liquid electrolyte is the key to success. 

Isopiestic or isothermal distillation. This technique can be useful for the preparation of metal-free solutions of volatile acids and bases for use in trace metal studies. The procedure involves placing two beakers, one of distilled water and the other of a solution of the material to be purified, in a desiccator. The desiccator is sealed and left to stand at room temperature for several days. The volatile components distribute themselves between the two beakers whereas the non-volatile contaminants remain in the original beaker. This technique has afforded metal-free pure solutions of ammonia, hydrochloric acid and hydrogen fluoride. 

The principal constituents of the paniculate matter are lead/zinc and iron oxides, but oxides of metals such as arsenic, antimony, cadmium, copper, and mercury are also present, along with metallic sulfates. Dust from raw materials handling contains metals, mainly in sulfidic form, although chlorides, fluorides, and metals in other chemical forms may be present. Off-gases contain fine dust panicles and volatile impurities such as arsenic, fluorine, and mercury. 

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