Cerium amalgam

Alloys of reactive metals are often more pyrophoric than the parent metals. Examples are alloys of titanium with zirconium thorium with copper, silver or gold uranium with tin, lead or gold magnesium with aluminium hafnium with iron [1], Cerium amalgams and thorium-silver alloys are spontaneously flammable when dry [2], Individually indexed alloys are ... 

Cerium amalgam, Ce/Hg. Caution. Ce/Hg burns immediately on contact with air. This amalgam is prepared by treatment of small pieces of the metal with a solution of HgCl2 in C2H5OH (2 minutes) followed by several washes with C2H5OH under N2. It is dried in vacuum. 

HOMOALLYLIC ALCOHOLS Cerium amalgam. Chromium(II) chloride. Fluorodimethoxyborane. Hypochlorous acid. Lithium bronze. Manganesc(II) chloride-Lithium aluminum hydride. Methylenetriphenylphosphorane. Organotitanium reagents. Tetrakis(triphenylphosphine)palladium. Tin. Tin(II) fluoride. 

Catechol estrogens, 157 Celacinnine, 590 Ceric pyridinium chloride, 184 Cerium amalgam, 114 Cerium(IV) ammonium nitrate. 184 Cerium(IV) ammonium nitrate-sodium hmmatc. 114... 

Cement, laboratory, 189 Cerium amalgam, 15 Cesium, metallic, 79 Chloroamine, 59 Chlorides, anhydrous, 28, 29 of silicon, 42 Chloroplumbic acid, 48 Chromi-oxalates, 37 Chromous acetate, 122 Chromous chloride, 124, 125 solution, 124 tetrahydrate, 126 trihydrate, 126 Cinnabar, 20 Cobalti-oxalates, 37... 

Cement, laboratory, 1 189 Cerite, extraction of, 2 44 Cerium, phosphor containing strontium sulfide and, 3 23 separation of, from rare earth mixtures, 2 43, 47, 48 test for, 2 50 Cerium amalgam, 1 15 Cerium-group earths, separation of, from yttrium earths by doublesulfate method, 2 44, 46 Cerium (III) magnesium nitrate, 2Ce(N03)s-3Mg(N03)2-24H,0, separation of praseodymium from lanthanum by, 2 57 Cerium(III) nitrate, 2 51 Cerium (IV) nitrate, basic, 2 49 Cesium, cesium azide for preparation of, 1 79... 

Cerium enolates may also be generated reductively in THF from a-iodo or a-bromo esters in the presence of an aldehyde or ketone using cerium metal turnings and catalytic HgCh (or cerium amalgam).35 This leads to a Reformatsky-type reaction (Volume 2, Chapter 1.7) producing the p-hydroxy ester (47) as a mixture of diastereomers (equation 16). 

Allyl iodide reacts in situ with cerium amalgam to generate allyl cerium iodide, which in turn reacts with ketones to give homoallylic alcohols to good yields (Imamoto et al., 1981). 

Imamoto et al. (1984c) reported a detailed investigation of carbon-carbon bond formation promoted by cerium amalgam and by organocaium(III) reagents gener-... 

For the reasons outlined last year (5,162), explorations of the reaction of various 2-alkenyl organometallic species with aldehydes and ketones to produce homoallylic alcohols, and its stereochemical outcome, have continued unabated. Two new approaches, shown in Scheme 20, are both analogous to Grignard reactions in one, allyl iodide is treated with cerium amalgam in the presence of a ketone, and in the other allylic bromides or iodides in the presence of metallic tin react with allylic inversion with a wide range of aldehydes and... 

Originally, general methods of separation were based on small differences in the solubilities of their salts, for examples the nitrates, and a laborious series of fractional crystallisations had to be carried out to obtain the pure salts. In a few cases, individual lanthanides could be separated because they yielded oxidation states other than three. Thus the commonest lanthanide, cerium, exhibits oxidation states of h-3 and -t-4 hence oxidation of a mixture of lanthanide salts in alkaline solution with chlorine yields the soluble chlorates(I) of all the -1-3 lanthanides (which are not oxidised) but gives a precipitate of cerium(IV) hydroxide, Ce(OH)4, since this is too weak a base to form a chlorate(I). In some cases also, preferential reduction to the metal by sodium amalgam could be used to separate out individual lanthanides. 

Mercury forms amalgams with numerous metals. Usually, this conversion is very exothermic, therefore it can present risks the reaction can become violent if a metai is added too quickly into mercury. Accidents have been described with caicium (at 390°C), aluminium, alkali metals (lithium, sodium, potassium, rubidium) and cerium. Some of these alloys are very inflammable, in particular the Hg-Zn amalgam. 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

Sodium aluminum chloride, 435 Sodium amalgam, 310, 416-417 Sodium amide-Sodium r-butoxide, 417-418 Sodium azide-Triphenylphosphine, 418 Sodium bis(2-methoxyethoxy)aluminum hydride, 166,418-420 Sodium borohydiidc, 323,420-421 Sodium borohydride-Alumina, 421 Sodium borohydride-Bis(2,4-pentane-dionato)copper(ll), 421 Sodium borohydride-Cerium(Ill) chloride,... 

The classical chemical methods to separate lanthanoids were based upon the redox behavior of Ce, Sm, Eu, and Yb , Other classical methods (fractional crystallization) are essentially physical processes. Cerium is oxidized to the 4-I- state and separated from the 3+ rare earths by solvent extraction, iodate precipitation, or selective hydrolysis or precipitation of basic Ce(IV) compounds in weakly acidic solution. Europium is reduced and maintained in H2O as Eu " by Zn amalgam and precipitated as EUSO4. Sm and Yb are extracted from H2O by reduction into dilute Na or Li amalgam. 

The purification of cerium is Imst accomplished according to Ilirsch hy forming the amalgam mid skimming the impurities off from the surface of the molten mass, The mercury may then lie distilled away by heating to a higher temperature in a vneimni. 

I With samarium-europium samples, other cerium earths are extracted from the amalgam phase only after the bulk of it has decomposed. Fractional decomposition of the amalgam is thus desirable. 

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