Electrolytic aluminum, preparation

Forty and co-workers have used electron yield EXAFS to study (ex-situ) anodic films on aluminum prepared in tartrate and phosphoric acid electrolytes. The A1—O distance is different for the two film preparations. They conclude from these studies that in the tartrate formed film 80% of the aluminum ions are in octahedral sites and 20% in tetrahedral sites whereas for the films formed in phosphoric acid all of the aluminum ions appear to be located at tetrahedral sites. In addition, immersion of the phosphoric acid generated films into water at 85° C for 4 hr. gave rise to dramatic changes in the structure which were ascribed to hydration. (Fig. 13) No such changes were noted for the films generated in tartrate electrolyte. 

The electrolytes were prepared using water, ethyl alcohol, ethyleneglycol, dimethylformamide as solvents of the current-conducting additives. The currentconducting additives were tartaric acid, potassium nitrate, ammonium nitrate and aluminum nitrate. The thicknesses of the synthesized AOS films were measured by laser ellipsometer in 5 points on the surface. Their dielectric characteristics were estimated from C-V curves also in 5 points. 

Hexafluorozirconic acid is used ia metal finishing and cleaning of metal surfaces, whereas the fluorozirconates are used in the manufacture of abrasive grinding wheels, in aluminum metallurgy, ceramics industry, glass manufacturing, in electrolytic cells, in the preparation of fluxes, and as a fire retardant (see Abrasives Metal surface treati nts). 

Examples of similar processes are the decomposition of precipitated aluminum trHiydroxide to alumina, which is the feed for the electrolytic production of aluminum metal, and the drying of wet sulfide concentrates in preparation for flash roasting (see Aluminumand aluminum alloys). 

Good yields of phenylarsine [822-65-17, C H As, have been obtained by the reaction of phenylarsenic tetrachloride [29181-03-17, C H AsCl, or phenyldichloroarsine [696-28-6], C3H3ASCI25 with lithium aluminum hydride or lithium borohydride (41). Electrolytic reduction has also been used to convert arsonic acids to primary arsines (42). Another method for preparing primary arsines involves the reaction of arsine with calcium and subsequent addition of an alkyl haUde. Thus methylarsine [593-52-2], CH As, is obtained in 80% yield (43) ... 

The products of this electrolysis have a variety of uses. Chlorine is used to purify drinking water large quantities of it are consumed in making plastics such as polyvinyl chloride (PVC). Hydrogen, prepared in this and many other industrial processes, is used chiefly in the synthesis of ammonia (Chapter 12). Sodium hydroxide (lye), obtained on evaporation of the electrolyte, is used in processing pulp and paper, in the purification of aluminum ore, in the manufacture of glass and textiles, and for many other purposes. 

The quality of the refined metal, and the current efficiency strongly depend on the soluble vanadium in the bath and the quality of the anode feed. As the amount of vanadium in the anode decreases, the current efficiency and the purity of the refined product also decrease. A laboratory preparation of the metal with a purity of better than 99.5%, containing low levels of nitrogen (30-50 ppm) and of oxygen (400-1000 ppm) has been possible. The purity obtainable with potassium chloride-lithium chloride-vanadium dichloride and with sodium chloride-calcium chloride-vanadium dichloride mixtures is better than that obtainable with other molten salt mixtures. The major impurities are iron and chromium. Aluminum also gets dissolved in the melt due to chemical and electrochemical reactions but its concentrations in the electrolyte and in the final product have been found to be quite low. The average current efficiency of the process is about 70%, with a metal recovery of 80 to 85%. 

There are a few reports of poly(naphthalene) thin films. Yoshino and co-workers. used electrochemical polymerization to obtain poly(2,6-naphthalene) film from a solution of naphthalene and nitrobenzene with a composite electrolyte of copper(II) chloride and lithium hexafluoroarsenate. Zotti and co-workers prepared poly( 1,4-naphthalene) film by anionic coupling of naphthalene on. platinum or glassy carbon electrodes with tetrabutylammonium tetrafluoroborate as an electrolyte in anhydrous acetonitrile and 1,2-dichloroethane. Recently, Hara and Toshima prepared a purple-colored poly( 1,4-naphthalene) film by electrochemical polymerization of naphthalene using a mixed electrolyte of aluminum chloride and cuprous chloride. Although the film was contaminated with the electrolyte, the polymer had very high thermal stability (decomposition temperature of 546°C). The only catalyst-free poly(naphthalene) which utilized a unique chemistry, Bergman s cycloaromatization, was obtained by Tour and co-workers recently (vide infra). 

Nitroso compounds are usually not obtained directly but rather by reoxidation of hydroxylamino compounds or amines. Hydroxylamino compounds are prepared by electrolytic reduction using a lead anode and a copper cathode [573], by zinc in an aqueous solution of ammonium chloride [574 or by aluminum amalgam [147], generally in good yields. 

V-Acylsaccharins prepared by treatment of the sodium salt of saccharin with acyl chlorides were reduced by 0.5 molar amounts of sodium bis(2-methoxyethoxy)aluminum hydride in benzene at 0-5° to give 63-80% yields of aliphatic, aromatic and unsaturated aldehydes [1108 Fair yields (45-58%) of some aliphatic aldehydes were obtained by electrolytic reduction of tertiary and even secondary amides in undivided cells fitted with platinum electrodes and filled with solutions of lithium chloride in methylamine. However, many secondary and especially primary amides gave 51-97% yields of alcohols under the same conditions [130]. 

Coke is obtained by destructive distillation or carbonization of bituminous coal, coal-tar pitch and petroleum produced during petroleum cracking. Coke from bituminous coal is used to reduce iron ore in blast furnaces and to produce synthesis gas. Petroleum coke or that obtained from coal-tar pitch is used in electrolytic reduction of aluminum oxide to aluminum and in the preparation of several metal carbides.. ... 

Lithium carbonate is used in enamels, specialty glasses and special ceramic wares. It is used to produce glazes on ceramics and porcelains. It also is used as an additive to molten aluminum fluoride electrolyte in Hall-Heroult process. It is the starting material to prepare many other hthium salts. The compound also is used in medicine as an antidepressant. 

The development of ionic liquids dates to 1914. The first research efforts involved the synthesis of ethylammonium nitrate. Hurley and Wier at the Rice Institute in Texas, 1948, developed the first ionic liquids with chloro-aluminate ions as bath solutions for electroplating aluminum. These liquids were studied primarily for their applications as electrolytes in electrochemistry technologies such as electroplating, batteries and alloy preparations. 

Also, the influence of aluminum sulfate, animal glue, and an extract of horse-chestnut nuts on zinc electrowiiming from a weak acidic sulfate electrolyte prepared from an industrial waste product was investigated [401]. The use of additives mixture has a beneficial effect on zinc electrowinning and results in smooth, slightly bright zinc deposits. 

When the Abbe Hauy pointed out the close similarity and probable identity of beryl and the emerald, Vauquelin analyzed them carefully, and found in 1798 that they are indeed identical, and that they contain a new earth, which he named glucina, but which is now known as beryllia The metal was isolated thirty years later by Wohler and Bussy independently. Boron was isolated in 1808 by Gay-Lussac and Thenard in France and by Davy in England by reduction of boric acid with potassium. Although amorphous silicon was prepared by Berzelius in 1824, the crystalline form of it was not obtained until about thirty years later, when Henri Sainte-Clarie DeviUe prepared it by an electrolytic method Aluminum was isolated in 1825 by the Danish physicist, Oersted, and two years later Wohler prepared it by a better method. Successful commercial processes for the manufacture of this important metal were perfected by Henri Sainte-Claiie Deville, by Charles Martin Hall, and by Dr. Paul L. T. Heroult. 

Paul-Louis-Toussaint Heroult. 1863-1914. French metallurgist. Independent discoverer of the electrolytic method of preparing aluminum now known as the Hall-Heroult process. He designed electric furnaces, and made many important contributions to the electrometallurgy of iron and steel... 

Birth of P.-L.-T. Heroult and of Charles Martin Hall, independent discoverers of the electrolytic process for preparing metallic aluminum. 

Fig. 1.1.10 Tile electrophoretic mobilities of aluminum hydrous oxide sols prepared by aging at 98°C for 24 h a 1 X 10-3 mol dm-3 solution of Al2(S04)t and treated as follows A, original sol at room temperature , sol freed of the original electrolyte by centrifugation and redispersed in dilute NaOH solutions O, pH of the sol adjusted to 9.7 by NaOH, followed by deionization, and redispersion at various pH values.

Numerous methods for the synthesis of salicyl alcohol exist. These involve the reduction of salicylaldehyde or of salicylic acid and its derivatives. The alcohol can be prepared in almost theoretical yield by the reduction of salicylaldehyde with sodium amalgam, sodium borohydride, or lithium aluminum hydride by catalytic hydrogenation over platinum black or Raney nickel or by hydrogenation over platinum and ferrous chloride in alcohol. The electrolytic reduction of salicylaldehyde in sodium bicarbonate solution at a mercury cathode with carbon dioxide passed into the mixture also yields saligenin. It is formed by the electrolytic reduction at lead electrodes of salicylic acids in aqueous alcoholic solution or sodium salicylate in the presence of boric acid and sodium sulfate. Salicylamide in aqueous alcohol solution acidified with acetic acid is reduced to salicyl alcohol by sodium amalgam in 63% yield. Salicyl alcohol forms along with -hydroxybenzyl alcohol by the action of formaldehyde on phenol in the presence of sodium hydroxide or calcium oxide. High yields of salicyl alcohol from phenol and formaldehyde in the presence of a molar equivalent of ether additives have been reported (60). Phenyl metaborate prepared from phenol and boric acid yields salicyl alcohol after treatment with formaldehyde and hydrolysis (61). 

Finally, Majda has investigated a novel inorganic membrane-modified electrode [32]. The membrane used was a microporous alumina prepared by anodizing metallic aluminum in an acidic electrolyte [33]. Majda et al. lined the pores of these membranes with polymers and self-assembled monolayers and studied electron and ion transfer down the modified pore walls to a substrate electrode surface [32]. Martin and his coworkers have used the pores in such membranes as templates to prepare nanoscopic metal, polymer, and semiconductor particles [34],... 

The only practical method for the preparation of pinacol hydrate is the reduction of acetone and the procedure described above is a modification of that of Holleman.1 The more common reducing agents that have been used are magnesium amalgam,2 aluminum amalgam,3 sodium,4 and sodium amalgam.5 Electrolytic reduction has also been used.6 1 Rec. trav. chim. 25, 206 (1906). 

Hydrogen fluoride is used to prepare fluorocarbons and one-third of the total goes to the aluminum industry, where synthetic cryolite, sodium aluminum fluoride, is a major constituent of the electrolyte. It is also consumed in the melting and refining of secondary aluminum. Other uses of hydrofluoric acid are found in the metals and petroleum industries. 

The apparently simple procedures of partial dehydrogenation of pyrrolidines and partial hydrogenation of pyrroles afford Zl1-pyr-rolines. However, the reaction is complex and is of little preparative value.97-98 A 1-Pyrrolines may be obtained by isomerization of A 3-pyrrolines.100 From the preparative point of view, partial hydrogenation of quaternary pyridine salts in strongly alkaline media to give 1-alkyl-id 2-piperideines is more important.101 Formation of heterocyclic enamines was observed in the reduction of i -methyl-pyrrolidone with lithium aluminum hydride,102 -alkylpiperidones with sodium in ethanol,103,104 and in the electrolytic reduction of N-methylglutarimide.106... 

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