Uranium disulphide

A hydrated uranium disulphide is obtained as a black precipitate when a solution of a uranous salt is treated with an alkali sxflphide. It is unstable and oxidises on exposure to air. 

E.F.Westrum Jr. has published low-temperature heat capacities for uranium disulphide, US2. Use these values to determine the absolute molar entropy at 298 K. 

Uranium disulphide is a particularly simple case, because it is solid throughout the experiment, and exists in only one crystalline form. Many compounds, however, undergo solid modifications or phase changes. These changes are easily catered for, because they occur at fixed temperatures. 

Table 5.1 Heat capacity data for uranium disulphide...

Figure 5.3 Heat capacity and temperature graph for determination of absolute entropy of uranium disulphide.

Potassium sulphide Rhenium (VII) sulphide Silver sulphide Sodium disulphide Sodium polysulphide Sodium sulphide Tin (II) sulphide Tin (IV) sulphide Titanium (IV) sulphide Uranium (IV) sulphide... 

The crystal structures of a number of diphosphine disulphides (121) and (122) show a remarkable constancy in the bond lengths. Two types of molecule are observed in the crystal of the tetramethyl compound (121, X = Y = Me). The crystal structure of triphenylphosphine oxide (P—C 176 pm, P—O 164 pm) varies little from that observed in the uranium oxide complexes, and does not confirm P—O bond lengthening in complexes, as indicated by vp=.o (see Section 3C). 

Compounds Bis-dimethylstibinyl oxide Bis(dimethylthallium) acetylide Butyllithium Nonacarbonyldiiron Octacarbonyldicobalt Pentacarbonyliron Tetracarbonylnickel Dibismuth trisulphide Dicaesium selenide Dicerium trisulphide Digold trisulphide Europium (II) sulphide Germanium (II) sulphide Iron disulphide Iron (II) sulphide Manganese (II) sulphide Mercury (II) sulphide Molybdenum (IV) sulphide Potassium sulphide Rhenium (VII) sulphide Silver sulphide Sodium disulphide Sodium polysulphide Sodium sulphide Tin (11) sulphide Tin (IV) sulphide Titanium (IV) sulphide Uranium (IV) sulphide ... 

Uranium Oxysulphide, U3O2S4 or UO3.2US2, is formed when uranous oxide, urano-uranic oxide, or ammonium uranate is heated in a stream of hydrogen sulphide or carbon disulphide vapour when one of the oxides is heated with a mixture of ammonium chloride and sulphur or when uranyl sulphate is heated in hydrogen or with potassium pentasulphide. It is a greyish-black powder, which is decomposed by nitric acid %vith deposition of sulphur. 

The disulphides of thorium and uranium are essentially covalent compounds but materials of the formula M2S3 appear to be semi-metallic, except for PugSg which is covalent. This again emphasises the increasing stability of compounds with the charge number +3 as the atomic number increases. 

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