Cerium solutions

The cerium solution concentration profiles from the mixingcell experiments often show considerable data scatter (2) The largest scatter was observed in GGW at 60°C with the 20-week preconditioned surface (DFO fit variance of 0 218). Filtration of... 

Standard cerium solution 1 mg/ml. Dissolve 0.1228 g of cerium(IV) oxide, Ce02 (dehydrated by ignition), in 5 ml of hot FICl (1+1), and add 0.1 g of NFI2OH.HCI. Dilute the solution to volume with water in a 100-ml standard flask. 

Standard cerium solution 1 mg/ml. Dissolve 3.1000 g of Ce(N03)3.6H20 in water, add 2 ml of cone. HNO3, and dilute to 1 litre in a standard flask. 

Cerium was added to the support by two different procedures, both based in the incipient wetness method. In the first procedure, zirconium hydroxide was impregnated with aqueous cerium (IV) nitrate in order to get 1 % wt of cerium in the support (support A). The second procedure consisted of calcining the hydroxide at 700 C for 4 h to obtain the oxide and then impregnation with the same cerium solution (support B). In both cases the incipient wetness technique was used to impregnate the solid. Zirconium oxide with no cerium added was prepared by calcining the hydroxide at 700 C. 

Fig. 16. Division of two images of rat stomachs, one containing a gadolinium and the other one a cerium solution. One of the images was recorded with tantalum as the target material while for the other gadolinium was used (From Ref. [67]).

Both kinds of waves are easily produced experimentally. Kinematic waves can be observed using the same recipe for oscillations given at the beginning of Chapter III. To produce spatial inhomogeneity, dissolve the malonic acid and sodium bromate in sulphuric acid along with a few mis of Ferroin in the bottom of an ungraduated cylinder. In a separate beaker dissolve the cerium salt in about 100 ml of water. Then carefully pipette the cerium solution on top of the sulphuric acid solution (it will float). With a glass rod mix the... 

Fig. 11.2. Cerium solute contribution to the electrical resistivity of YCe alloys, normalized to its value at 0 K, vs temperature. The Ce contribution at 0 K is equal to 12.0 1.5 ftH cm/at.% Ce [after Sugawara and Yoshida (1968)].

Among the complex nitrates of tetravalent cerium the well-known compoimd (NH4)2[Ce(N03)g] has been structurally characterized by single crystal methods (Beineke and Delgaudio, 1968) (see fig. 82). This compound was earlier used in industrial separation processes aimed at the production of pure cerium oxide (Smith et al., 1936). It also is used in quantitative analytical determinations for the preparation of standard cerium solutions (Petzold, 1955). 

Figure 1 shows the pore size distribution for a series of ceria samples prepared in the presence of differing amounts of aniline. It is evident that the effect of precursor cerium ions coneentration on both pore volume and on the pore size distribution is much more important than that of aniline concentration, although the latter does appear to influence Sbet as discussed earlier. It is clear from Figure 1 that the sample prepared from a O.IM cerium solution has very ill-defined pores with a very widely spread size distribution and very low total pore volume. When the precursor concentration was increased to 0.0 IM this led to a more narrow size distribution, but still relatively low total pore volume. On the other hand, at even lower cerium concentrations, there is a more marked increase in pore volume, but whereas the pore size distribution shows a marked maximum value, there is a fairly wide distribution of pore diameter values, from 2nm to 7,5nm for 0.005M and lOnm for O.OOIM precursor concentration. It should be noted that aniline concentration was kept constant. 

Figure 2 contains the X-ray diffractogramme for ceria prepared from 0.05M cerium solution and IM aniline. The major peaks present were those of the poorly crystalline fluorite ceria phase previously identified [see, for example, 6]. However, contrary to what obtains for other samples presented in this paper, extra peaks have appeared in the diffractogramme for this sample, in the 20 region 10 to 20 . 

In this manner the hydrated cerinm oxide coating provided a barrier which protected the alloy. Repair of coating flaws was possible while the specimen remained exposed to a reservoir of cerium ions in solution. In this fashion the system of hydrated cerium oxide barrier coating and the cerium solution was analogous to the chromate conversion coating, which provided protection via the hydrated CitHI) oxide barrier film and leachable chromate ions," except in the case of chromate, the healing species was built into the coating. 

The surface species then proceeds to react with cerium solution species via... 

Consider the estimation of iron(II) ions by cerium(IV) ions in aqueous solution ... 

Experimentally, the aqueous iron(II) is titrated with cerium(IV) in aqueous solution in a burette. The arrangement is shown in Figure 4.6, the platinum indicator electrode changes its potential (with reference to a calomel half-cell as standard) as the solution is titrated. Figure 4.7 shows the graph of the cell e.m.f. against added cerium(IV). At the equivalence point the amount of the added Ce (aq) is equal to the original amount of Fe (aq) hence the amounts of Ce (aq) and Fe (aq) are also equal. Under these conditions the potential of the electrode in the mixture is ( - - f)/2 this, the equivalence point, occurs at the point indicated. 

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. 

Ceric sulfate, O.IA Ce(lV) to Ce(lll). Dissolve 63.26 g of cerium(lV) ammonium sulfate dihydrate in 500 mL of 2N sulfuric acid. Dilute the solution to 1 L and standardize against the... 

Hydrolysis is very extensive in Pu(IV) solutions, less so in Pu(Ill) and Pu(VI), and least in Pu(V). The chemical properties of Pu(IV) are somewhat similar to those of Ce(IV) and U(IV) (see Cerium AND cerium compounds). The hydrolysis thermodynamics of Pu(IV) have been assessed in perchlorate solutions (105). The first hydrolysis equiUbrium is... 

An alternative process for opening bastnasite is used ia Chiaa high temperature roastiag with sulfuric acid followed by an aqueous leach produces a solution containing the Ln elements. Ln is then precipitated by addition of sodium chloride as a mixed sulfate. Controlled precipitation of hydroxide can remove impurities and the Ln content is eventually taken up ia HCl. The initial cerium-containing product, oace the heavy metals Sm and beyond have been removed, is a light lanthanide (La, Ce, Pr, and Nd) rare-earth chloride. 

The ESR spectrum of the pyridazine radical anion, generated by the action of sodium or potassium, has been reported, and oxidation of 6-hydroxypyridazin-3(2//)-one with cerium(IV) sulfate in sulfuric acid results in an intense ESR spectrum (79TL2821). The self-diffusion coefficient and activation energy, the half-wave potential (-2.16 eV) magnetic susceptibility and room temperature fluorescence in-solution (Amax = 23 800cm life time 2.6 X 10 s) are reported. 

Ln(II) in LnFj Ln(II) were determined after samples dissolution in H PO in the presence of a titrated solution of NFI VO, which excess was titrated with the Fe(II) salt. It was found that dissolution of the materials based on CeF CeFj in H PO does not change the oxidation state of cerium, thus phosphate complexes of Ce(III, IV) can be used for quantitative spectrophotometric determination of cerium valence forms. The contents of Ln(II, III) in Ln S LnS may be counted from results of the determination of total sulfur (determined gravimetric ally in BaSO form) and sum of the reducers - S and Ln(II) (determined by iodometric method). 

To determine of Ce(IV) in acid soluble single crystals, a simple and sensitive method is proposed. The method is based on the reaction of tropeoline 00 oxidation by cerium(IV) in sulfuric acid solution with subsequent measurement of the light absorption decrease of the solution. The influence of the reagent concentration on the analysis precision is studied. The procedure for Ce(IV) determination in ammonium dihydrophosphate doped by cerium is elaborated. The minimal determined concentration of cerium equal to 0.04 p.g/ml is lower than that of analogous methods by a factor of several dozens. The relative standard deviation does not exceed 0.1. 

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