14 Faraday Fluoride

According to Faraday s law, one Faraday (26.80 Ah) should deposit one gram equivalent (8.994 g) of aluminum. In practice only 85—95% of this amount is obtained. Loss of Faraday efficiency is caused mainly by reduced species ( Al, Na, or A1F) dissolving or dispersing in the electrolyte (bath) at the cathode and being transported toward the anode where these species are reoxidized by carbon dioxide forming carbon monoxide and metal oxide, which then dissolves in the electrolyte. Certain bath additives, particularly aluminum fluoride, lower the content of reduced species in the electrolyte and thereby improve current efficiency. 

Photochlorination of tetrachloroethylene, observed by Faraday, yields hexachloroethane [67-72-1]. Reaction with aluminum bromide at 100°C forms a mixture of bromotrichloroethane and dibromodichloroethane [75-81-0] (6). Reaction with bromine results in an equiUbrium mixture of tetrabromoethylene [79-28-7] and tetrachloroethylene. Tetrachloroethylene reacts with a mixture of hydrogen fluoride and chlorine at 225—400°C in the presence of zirconium fluoride catalyst to yield l,2,2-trichloro-l,l,2-trifluoroethane [76-13-1] (CFG 113) (7). 

Interest in solids with highly mobile ionic species is not new. In 1839, Michael Faraday reported measurements on several materials including lead fluoride (Pbp2) that showed an unusual increase in the electrical conductivity at elevated temperatures, contrary to that found in normal metals. This finding was a surprising discovery, since most simple salts are not good conductors of electricity. 

Although Faraday discovered the unusual electrical properties of lead fluoride, he did not explain his observations. It is now known that the high electrical conductivity of Pbp2 is due to the motion of F ions, not electrons. At 500-700 °C, fluoride ions diffuse rapidly through the Pbp2 lattice. Pbp2 was the first example of a solid with high ionic conductivity. 

The spectrum of the Eu2+ (4/ ) ion both in aqueous solution [593] and in the solid state [594—598] has been studied by a number of people. In addition to the usual very strong, broad fn - fn 1d transitions, weak, sharp lines are also observed in the ultraviolet region. These weak lines may possibly be due to the transitions from 8 7/2 to the 6P, Z and D terms of the p configuration. The Faraday rotation measurements [549] on Eu2+ in the cubic fluoride lattice showed that the upper level contained some Pj character. 

In 1834, M. Faraday thought that he had obtained fluorine in a separate state by electrolyzing fused fluorides, but later, he added ... 

A. E. Barton and B. J. Howard, Faraday Discuss. Chem. Soc., 73,45 (1982). An Intermolecular Potential-Energy Surface for Hydrogen Fluoride Dimer. 

Aluminum Fluoride, Aluminum trifluoride. A1F3 mol wt 83.98. Al 32.13%, F 67.87%. Prepd by heating (NHjIjAIFj to red heat in a stream of nitrogen Witt. Bar-row, Trans. Faraday Soc. 55, 730 (1959) Kwasntk in Handbook of Preparative Inorganic Chemistry, Vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) p 225. Review Kemmltt, Sharp, Advan. Fluorine Chem. 4, 154-155 (1965). 

The adsorption of nitrous oxide on barium fluoride has been determined at five temperatures by Crawford and Tompkins (Trans. Faraday Soc. 1948, 44, 698, and private communication). Their measurements are given in table 1, where f denotes the pressure and v the volume at s.t.p. of nitrous oxide adsorbed. 

Gore investigated anhydrous hydrofluoric acid, determined its vapour density, etc., and its action on many elements and salts. He attempted to electrolyse it (and verified Faraday s result), and also fused silverfluoride. He heated silver fluoride in a platinum boat in a platinum vessel filled with chlorine, when the boat was corroded to a reddish-brown substance (platinum fluoride). With a graphite boat a gas (CF4 ) was formed. No fluorine was obtained. Such was the state of knowledge when Moissan began his research. 

And at last the moment came when A. Moissan took resolutely in his hands the fate of fluorine. First of all, he analysed the errors of his predecessors and clearly realized that the attempts of Faraday, E. Fremy, and G. Gore had failed because they could not subdue the fury of fluorine which instantly reacted with the material of the apparatus. Moissan was also aware of the mistake of those investigators who tried to isolate fluorine by the action of chlorine on fluorides chlorine had to be a weaker oxidizer than fluorine. 

Reed CL, Kono M, Langford SR et al (1997) Ultraviolet photodissociation dynamics of formyl fluoride.2. Energy disposal in the H -I- FCO product channel. J Chem Soe, Faraday Trans 93 2721-2729... 

Ogilvie J, Uehara H, Horiai K (1995) Vibration-rotational spectra of GaF and molecular properties of diatomic fluorides of elements in group 13. J Chem Soc Faraday Trans 91 3007-3013... 

Bunn CW, Alcock TC (1945) The texture of polyethylene. Trans Faraday Soc 41 317-325 Cardoso VF, Minas G, Lanceros-Mendez S (2012) Multilayer spin-coating deposition of poly (vinylidene fluoride) films for controlling thickness and piezoelectric response. Sens Actuators A Phys 192 76-80... 

Ainslie B.J., Davey S.T., Szebesta D., Williams J.R., Moore M.W., Whitley T, Wyatt R. A review of fluoride fibers for optical amplification. J. Non-Cryst. Solids 1995 184 225-228 An C.T., Zhou X.P. Activation of O2 over Srp2- and Bap2-promoted SmOF catalysts for the oxidative dehydrogenation of ethane. J. Chem. Soc., Faraday Trans. 1997 93 485-491 Auzel F., Pecile D., Morin D. Rare earth doped vitroceramics new, efficient, blue and green emitting materials for infrared up-conversion. J. Electrochem. Soc. 1975 122 101-107 Balaji T., Buddhudu S. Photoluminescence spectra ofEu +-dopcd certain powder phosphors. Spec-trosc. Lett. 1993 26 113-127... 

Recently a lot of reviews on ionic conductivity of inorganic fluorides were published. A short history of these investigations starting with Faraday s basic work of 1834 up to their current applications is presented in [2]. The structure and ionic conductivity of Pbi xAlxF2+x. Mi x(U or Th)xF2+2x (M = Ca, Sr, Ba, Pb) fluorites and CeFa, Cei yCdyF3 y tysoiutes are described in [5]. In a detailed review [6], various fluoride-conductive electrolytes perovskites MPbF3 (M = K, Rb, Cs), B-deficit perovskites - tysonites... 

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