Aluminum complexes fluorides

Both the binary and complex fluorides of aluminum have played a significant role in the aluminum industry. Aluminum trifluoride [7784-18-17, A1F., and its trihydrate [15098-87-0] 3 3H2O, have thus far remained to be the only binary fluorides of industrial interest. The nonahydrate [15098-89-2] 3 9H2O, and the monohydrate [12252-28-7, 15621 -55-3], AIF 20, are of only academic curiosity. The monofluoride [13595-82-9], AIF, and the difluoride [13569-23-8], AIF2, have been observed as transient species at high temperatures. 

Chromium Chromate. Chromium chromate treatment baths are acidic and made up from sources of hexavalent chromium and complex fluoride, fluorosiHcate, fluorozirconate, fluorotitanate, and siHcofluorides. Optional additional components added to accelerate coating rate are free fluoride, ferricyanide, and other metal salts such as barium nitrate. Conversion coating on aluminum precedes by the following reactions (2,3,17) ... 

Thus the complex fluorides of aluminum do not offer any advantages over other fluorinating agents in halogen-exchange reactions and so they have not found application in industry, although sodium hexafluoroaluminate is produced in large quantities. 

Add 2 g of sodium fluoride, boil the mixture for 2 to 5 min, and cool in a stream of running water. Titrate the EDTA (which is released by fluoride from its aluminum complex) with 0.01 M Zinc Sulfate to the same transitory yellow-brown or pink endpoint as described above. 

The Zr and Hf tetrahydroborates M(BH4)4 are the most volatile compounds of these elements, with boiling points of 123 and 118°C they are also very sensitive to oxidation and hydrolysis. They can be obtained by the reaction of the chlorides with alkali metal borohydrides or of the complex fluorides NaMFs with aluminum borohydride (the fluorides MF4 do not react), followed by distillation from the reaction mixture. According to low-temperature X-ray data, all the borohydride groups are tridentate in both M(BH4)4 complexes, which have Td symmetry. The same is trae for their substituted M(BH3Me)4 derivatives, that is, the metal atom is 12-coordinate. Proton NMR indicates fast exchange of bridging and terminal protons on the NMR timescale in these fluxional molecules see Fluxional Molecule). 

Assuming that Fe203 reacts with cryolite under the formation of fluoride and oxofluoride aluminum complexes according to the equation... 

For the yellow chromating of aluminum, solutions containing chromium(VI) compounds as well as simple or complex fluorides and activators are used to accelerate layer formation. The pH value is 1.5-2.5 at total bath concentrations of 5-20 g/L. The conversion layers consist of oxides or hydrated oxides of trivalent and hexava-lent chromium and aluminum. The color of the layer may range from colorless through yellowish iridescent to yellowish brown, corresponding to an increase in the surface weight from 0.1 to 3 g/m. ... 

Aqueous, chromium-free acidic solutions have also been developed for aluminum materials that may contain complex fluorides of titanium and zirconium, phosphate, and special organic compounds. These solutions are applied by spraying or dipping (up to 60 °C) and produce thin, almost colorless conversion layers with a surface weight < 0.1 g/m. ... 

Figure 7.19 KF-ethyl-aluminum complex or K2AI2C3H5F+ in toluene, K for the potassium ions, F for fluoride ion, and T for the toluene molecules.

Aluminum Complex formation with F " Stopped-flow technique, fluoride-selective electrode... 

Sample solutions measuring 50 pi were mixed with 350 pi 5 M HNO3 and 2.4 ml 0.1 M A1 (NOaja. The aluminum nitrate was used to complex fluoride ions. and disturbing nuclides (mainly lanthanides) were extracted into 1.0 M HDEHP (bis-2-ethylhexyl orthophosphoric acid) in Solvent 70 (an aliphatic kerosene) 2.0 ml of the aqueous phase was taken out, and... 

The value of the pH for optimum stability of silicic acid depends on what impurities are present in the solution. Traces of aluminum ions and to a lesser extent, iron, thorium, and beryllium ions tend to offset the effect of fluoride ion by forming complex fluorides and thus retard polymerization in this pH range. Depending on the purity of the solution, the pH of optimum stability may range from 1 to as high as 3-3.5. In silicic acid. solutions free from aluminum impurity, as little as 1 ppm of fluorine has a marked effect on the rate of polymerization in acid solution. 

The interferences of aluminum, sodium fluoride, and iron(lll) have been studied [13]. The results indicate that lowering the pH is recommended. Only small amounts of Fe(lll) can be present as higher concentrations could be removed by extraction with acetyl acetone complex with CCU-... 

B. Jensen, Phase and Structure determination of a New Complex Alkali Aluminum Fluoride, Institute of Inorganic Chemistry, Norwegian Technical University, Trandheim, 1969. 

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