Ceric salts

Ceric salt solutions are strongly acidic, basic salts tend to form readily, and there are no stable simple salts of weak acids. 

Ceri-oxyd, n. ceric oxide, cerium(IV) oxide, -salz, rt. ceric salt, cerium(IV) salt. sulfat, n. ceric sulfate, cerium(IV) sulfate. 

Mino and Kaizerman [12] established that certain. ceric salts such as the nitrate and sulphate form very effective redox systems in the presence of organic reducing agents such as alcohols, thiols, glycols, aldehyde, and amines. Duke and coworkers [14,15] suggested the formation of an intermediate complex between the substrate and ceric ion, which subsequently is disproportionate to a free radical species. Evidence of complex formation between Ce(IV) and cellulose has been studied by several investigators [16-19]. Using alcohol the reaction can be written as follows ... 

This technique is based in the fact that when cellulose is oxidized by ceric salts such as ceric ammonium nitrate Ce(NH4)2(N03)6 free radicals capable of initiating vinyl polymerization are formed on the cellulose. However, the possibility remains that the radical formed is an oxygen radical or that the radical is formed on the C-2 or C-3 instead of the C-6 carbon atom. Another mechanism, proposed by Livshits and coworkers [13], involves the oxidation of the glycolic portion of the an-hydroglucose unit. Several workers [14,15], however, have found evidence for the formation of some homopolymer. In the ceric ion method free radicals are first generated and are then capable of initiating the grafting process [16-18]. 

The treatment of polonium(lV) with nitric acid/potassium permanganate under reflux yields a sludge of manganese dioxide which contains all the polonium originally present the valency state is uncertain. Polonium (IV) in weighable amounts is not oxidized by persulfate, ceric salts or chlorine in alkaline solution (12), although trace scale work indicates that both ceric salts and dichromate do oxidize polonium to polonium(VI) (94). 

In aqueous solution, manganous salts are oxidised to manganese dioxide,6 and if silver nitrate is present as catalyst, to permanganate 0 the latter change constitutes Marshall s reaction. Chromium solutions in a similar manner give rise to chromate,7 even without a catalyst. Ferrous and cerous salts are converted into ferric and ceric salts, respectively, and phosphites are oxidised to phosphates. 

Cerium Thioarsenates.—The addition of sodium orthothio-arsenate to an aqueous solution of a cerous salt produces a pale yellow precipitate of cerous orthothioarsenate.1 With sodium hydrogen ortho-thioarsenate the precipitate approximates in composition to cerous pyro-thioarsenate. Ceric salts also give pale yellow precipitates, probably ceric orthothioarsenate. Thioarsenates of other rare earth metals have not been described. 

Richards, G. N. Initiation of graft polymerization on cellulose by hydroxyl radicals and by ceric salts. J. Appl. Polymer Sci. 5, 539 (1961). 

Mino, G., and S. Kaizerman, American Cyanamid Company Process for polymerization of a vinylidene monomer in the presence of a ceric salt and an organic reducing agent. U. S. 2,922,768 (January 26, 1960). 

Iwai, S., T. Kakurai, and T. Noguchi Studies on acrylonitrile-styrene graft copolymerization onto cellulose by ceric salt. J. Soc. Text, and Cell. Ind. (Japan) 19, 547 (1963). 

As the consequence of the use of large amount of ceric salt in copolymerization reaction severe deviation from the true value of grafting percentage may result if the initial products of graft copolymerization are oven-dried before removing homopolymers from the grafting system. 

When the redox potential was high enough we found no difference between p- and n-type material. Nitric acid is not a very convenient system to study because its redox reaction is in itself very complicated. The reduction scheme for nitric acid contains a step which appears to be catalyzed at the surface. The catalytic activity of a germanium surface is probably influenced by the doping perhaps this could explain your results. We did not find any difference in p- and n-type when we used ferri-cyanide or ceric salts as oxidizers. 

Consider, for example, a system of two ions M and M + which is slow in the attainment of equilibrium with the electrode, and suppose a very small amount of a ceric salt (Ce++++"i is added to act as potential mediator the reaction... 

Ceric ammonium nitrate or ceric sulfate is used to oxidize saturated and unsaturated secondary alcohols to ketones. The ceric salts are used only in catalytic amounts with sodium bromate as a reoxidant (equation 241) [741]. 

A more complicated but also very instructive and versatile process was published by Hydro Quebec, namely, the indirect oxidation of aromatics, specifically naphthalene, by ceric salts [9]. The electrolysis is only a small part of the process Cerous methanesulfonate is oxidized to ceric methanesulfonate. The organic part of the process takes place in a separate reactor The aqueous ceric salt oxidizes the organic substrate in a heterogeneous two-phase reaction that requires good mixing. After the separation of the aqueous and organic phases, the aqueous phase is extracted with a solvent that is recycled continuously. In a follow-up step, organic impurities must be removed from the cerous solution before it is fed back to the electrolysis. The product (naphthoquinone) has to be dried. 

Derivation By treating a solution of a ceric salt with strong alkali. Reagent grade is prepared by adding a saturated solution of ceric ammonium nitrate to an excess of ammonium hydroxide. 

Cerium forms the oxide CeOj, which is more stable than Ce 0 the series of ceric salts are well defined and stable compounds. Both praseo. dymium and terbium give higher oxides but neither of these forms a series of salts. Terbium peroxide has a brownish black color and is the most highly colored compound of the group. 

The ceric salts are derivatives of Ce02> which is feebly basic. As a consequence they are considerably hydrolyzed in solution and give an acid reaction. Normal ceric salts of weak adds are unknown, and even the chloride and nitrate are known only as double or complex salts. Reduction to cerous compounds is easily done in acid solution, but much more difficult to accomplish in alkaline media, Ceric compounds easily form colloidal solutions which do not appear to be basic salts of the ordinary type. 

Ceric oxide, Ce02, is prepared by igniting cerium or any cerous or ceric salt of an oxy-acid. Its density depends upon the method of preparation. The color is the subject of much discussion.) We would expect a white oxide like zirconia and thoria. White oxides have been prepared, but Brauner has shown that such ceria contains impurities. As usually obtained ceria has a pale yellow color. It volatilizes without melting or decomposition at about 1900°. Besides being a weak base it shows slight evidence of faintly acidic properties. While pure ceria is insoluble in nitric or hydrochloric acids, a mixture of rare earth oxides dissolves readily... 

Ceric hydroxide, Ce(OH)4, is not known. A hydrated oxide, probably Ce20(0H)6, forms as a yellow gelatinous precipitate when ammonia or an alkali hydroxide is added to a ceric salt. It may also be prepared by the oxidation of cerous hydroxide. It dissolves in nitric acid, forming a ceric salt, in sulfuric acid yielding a partially reduced product, and in hydrochloric acid giving cerous chloride and chlorine. 

Ceric nitrate, Ce(N03) 4, is not known as a simple salt, but double nitrates of the type Ce(N03)4 2 M N03 are formed with the alkali metals and ammonium. In aqueous solutions these salts are readily hydrolyzed, but they are the most stable ceric salts. The ammonium ceric nitrate is important in the purification of cerium. A series of double nitrates, M (N03)2 Ce(N03)4 8 H2O, is also formed, but they are less stable than the alkali double salts. When ceric hydroxide is evaporated with nitric acid, crystals of the basic salt 2 Ce0H(N03)2 9 H2O are obtained. 

Iron-gray, ductile, malleable metal face -cen tered cubic structure at room temp. Stable in dry air, but superficially oxidized in moist air when finely divided may ignite sponta -neously. d 6.77. mp 795". E (aq) Cei+ /Ce — 2,48 V (calc). Slowly dec by cold, rapidly by hot water sol in dil mineral adds. Ceric salts usually are yellow to orange-red in color tnd liberate iodine from KI. Cerous salts are usually white tnd give a white ppt with alkali hydroxides or sulfides, insol ineicess of reagent they also are pptd by ammonium oxalate from cold dil acid sols. 

Hexavalent plutonium is obtained by the action of strong oxidizing agents (ceric salts, dichromates, permanganates, or hot bromate soln contg nitric acid) on the tri - Or tetravalent form. Reduced to tri- or tetravalent plutonium by sulfur dioxide or ferrocyanide. 

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