Cerium sulphide

Perhaps the earliest system to be described as an Anderson transition was cerium sulphide (Cutler and Mott (1969), on the basis of observations by Cutler and Leavy (1964)). The material in question can be written Ce3 xvxS4, where v is a cerium vacancy, the vacancies being distributed at random. The field near a cerium vacancy repels electrons, because they are negatively charged. Variation of x, then, changes the number of electrons and the number of scatterers. Figure 1.25 shows some results on the conductivity. At that time the present author believed... 

Fig. 1.25 Resistivity p of cerium sulphide of various compositions as a function of temperatures. The electron concentrations (in 1018cm"3) are as follows A, 0.5 B, 5.2 C, 14 D, 83 E, 1420. From Cutler and Leavy (1964).

Gingerich et al. (1972) have observed a number of cerium sulphide species containing two cerium atoms per molecule. Smoes et al. (1977) have reported similar results for the eueropium-sulphur system. Table 19 summarizes the thermodynamic data of these sulphide species. 

Diisopropylberyllium Cerium Mercury (II) sulphide Trichloro(methyl)silane... 

Aluminium B a 5 o B B < I Antimony a < Barium B a 1 3 Bismuth I Boron Cadmium 1 Caesium Calcium 1 Cerium Chloride, Chlorine [ Chromium X) o o C o a Gallium I Germanium Gold 1 Hafnium Hydrogen sulphide B a 5 a B a 5 a o 1 Lanthanons Lead f Lithium 1 Magnesium f Manganese Mercury Molybdenum... 

Ammonia or ammonium sulphide solution white precipitate of cerium(III) hydroxide, Ce(OH)3 (or Ce203.xH20), insoluble in excess of the precipitant, but readily soluble in acids. The precipitate slowly oxidizes in the air, finally becoming converted into yellow cerium(IV) hydroxide, Ce(OH)4 (or Ce02.xH20). Sodium hydroxide solution gives a similar result. The precipitation is prevented by tartrates and citrates. 

Reducing agents (e.g. hydrogen sulphide, sulphur dioxide, hydrogen peroxide, and hydr iodic acid) These convert cerium(IV) ions into cerium(III). 

It maj- also be separated from solutions of uranium salts bj the addition of a little cerium salt and precipitation with aqueous hydrofluoric acid, or with oxalic acid or bj adding a small quantity of thorium nitrate and precipitating with t-nitrobenzoic acid. It may also be absorbed bj- charcoal,iDasic ferric acetate, and by various oxides, sulphides, sulphates, and gelatinous silica. In the case of charcoal the uranium X is completely removed from a solution of a... 

If this test is positive, remove phosphate (see Table 5.6 in Section 5.8). Among the less common ions, titanium, zirconiiun, cerium, thorium, and uranium will be completely precipitated by ammonia solution, and will therefore appear together with the other Group IIIA cations. Vanadium will only partly be precipitated here some of the vanadium present will be found in the filtrate of the sulphide precipitates of Group IIIB cations. Some of the thallium(I) partly removed with Group I will also appear in this Group some molybdenum will appear in the filtrate of Group IIIB sulphides. 

Until a few years ago, the red pigment for coloring containers, toys, household wares, plastic crates, etc. was Cadmium Red. This is Cadmium sulfoselenide red, C9Hi3CdN204SSe (CAS 58339-34-7), also known as Pigment Red 108 (see Chemnet 2015). The cadmium compound is now considered environmentally undesirable, so it is being replaced by the non-toxic Cerium(III) sulphide (Cc2S3 CAS 12014-93-6). This compound gives a rich red color and is stable up to 350 °C (Emsley 2001). 

Sulphides. Compounds of metals with the element sulphur. Some melt above 2000°C, though some decompose at much lower temperatures. Applications are as electroceramics, in solar cells and other energy conversion applications. Cadmium sulphide is a pigment, thorium sulphide a crucible material for cerium. 

The beneficial effects of Ce02 are also reported in the literature. It was found that sulphidation of FeAl alloys was retarded because the nanoparticles inhibit iron diffusion and act as traps for the sulphur ions [26]. Cabot and Foissy also demonstrated that silica layers stabilised with CeOz nanoparticles led to significant improvements in the corrosion resistance of zinc-coated steels [27]. Cerium oxides are also reported as having a pronounced stabilising effect on the passive state of steels and then-corrosion resistance [28]. 

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