Tantalum pentachloride

Another method of purifying niobium is by distillation of the anhydrous mixed chlorides (29). Niobium and tantalum pentachlorides boil within about 15°C of one another which makes control of the process difficult. Additionally, process materials must withstand the corrosion effects of the chloride. The system must be kept meticulously anhydrous and air-free to avoid plugging resulting from the formation of niobium oxide trichloride, NbOQ. Distillation has been used commercially in the past. 

The reaction temperature of 500—600°C is much lower than that required for the reductive chlorination. The volatile chlorides evolve from the molten salt bath. The boiling points of NbCl, TaCl, and WOCl He between 228 and 248°C. These compounds must therefore be separated by means of a distillation column. The chlorination of ferroalloys produces very pure tantalum pentachloride in toimage quantities. The TaCl contains less than 5 )J.g Nb/g Ta, and other metallic impurities are only amount to 1—2 lg/g Ta. 

Substitution of the fluoride ligands by ions that lead to higher covalence of the bonds can alter the mechanism of tantalum reduction. For instance, the investigation of pure chloride systems containing tantalum pentachloride,... 

Preparation by reaction of tantalum pentachloride with pure lithium dimethylamide in pentane is unsafe. Initial non-reaction is followed by explosion during manipulation of the slurry. Presence of ether or dimethylamine gives smooth reaction. Stepwise displacement of chlorine, starting with the free amine, is also recommended. 

Tantalum oxide film, 24 314 Tantalum oxides, 24 322, 334 Tantalum pentachloride, 24 335 Tantalum pentafluoride, 24 334-335 Tantalum pentoxide, electrochemical reduction of, 24 322 Tantalum powder, 24 323, 324-325 capacitor-grade, 24 326 safety of, 24 333-334 Tantalum products, world shipments of, 24 331t... 

Silver difluoride, 0014 Silver fluoride, 0013 Sodium chloride, 4036 Sodium iodide, 4623 Tantalum pentachloride, 4185 Tellurium tetrabromide, 0296 Thallium, 4922 Tin(II) chloride, 4116 Tin(IV) chloride, 4174 Tin(II) fluoride, 4331 Titanium(II) chloride, 4117 Titanium dibromide, 0284 Titanium diiodide, 4630 Titanium tetrachloride, 4176 Titanium tetraiodide, 4638 Titanium trichloride, 4158... 

Tantalum pentachloride is prepared by heating tantalum metal with excess chlorine ... 

Tantalum pentachloride is hydrolyzed by water to form hydrous tantalum pentoxide, Ta205 uH20 and hydrochloric acid ... 

Tantalum pentachloride forms adducts with donor solvent molecules. Also, it forms several complexes and organometaUic derivatives. 

Commercially available starting materials are employed for the preparations. Tantalum metal may be used in granular form (with 1 mm diameter) or as a powder. Tantalum pentachloride is extremely moismre-sensitive. It should be handled under strictly anhydrous conditions in a drybox or drybag. 

In a drybox or drybag, stoichiometric amounts of tantalum pentachloride (25.1 g, 70 mmol) and sodium chloride (5.84 g, 100 mmol) are intimately mixed by grinding in a mortar. The mixture is placed in the Vycor reaction tube (see Fig. 1), and excess tantalum powder (58 g, 320 mmol) is added. Using a gas/ oxygen torch, the reaction vessel is sealed under a dynamic vacuum near the midpoint of its neck. 

Balke in 191011 hydrolysed tantalum pentachloride, TaCl , to the pentoxide, Ta2Os, with water and a small quantity of nitric acid. The mean of eight experiments gave ... 

But the extreme values showed a difference of 0-46, from which it was concluded that the tantalum pentachloride used varied slightly in its composition, and that this salt is also unsuitable for use in the determination of the atomic weight. This conclusion has been confirmed.4... 

Tantalum Pentachloride, TaCl5, is the best known of the chlorides of tantalum. It has been prepared by several methods. ... 

Hydrates of Tantalum Pentoxide, Colloidal Tantalum Pentoxide, Tantalic Acid.—When tantalum pentachloride or pentabromide is treated with water, or when a solution of a tantalate is boiled with dilute acids, a gelatinous predpitate of more or less hydrated tantalum pentoxide is thrown down. Insoluble tantalates on fusion with potassium hydrogen sulphate and extraction of the melt with water give the gel. In dealing with double fluorides of tantalum it is necessary to remove all the hydrofluoric add by evaporation with concentrated sulphuric acid, otherwise double fluorides are obtained. 

Tritantalum Pentanitride, Ta3NE, has been obtained as a bright red, amorphous powder by passing ammonia over heated tantalum pentachloride. On being heated in air it forms the pentoxide, and when fused with caustic potash it evolves ammonia.9... 

Tantalum Carbide, TaC, has been prepared by heating a mixture of tantalum pentoxide and carbon in a molybdenum boat at 1260° C. in a stream of hydrogen,2 or by the action of hydrogen and carbon monoxide on tantalum pentachloride. It is a dark grey or black substance which is insoluble in all acids, and bums to the pentoxide when powdered and heated in air. Density—13 96. It melts with decomposition at 4100° abs., which is probably the highest melting-point yet recorded for a chemical compound. Its hardness coefficient fees between 9 and 10. It is a good conductor of electricity.4 For its crystal structure see reference cited.5... 

These are usually reactions of anhydrous transition and B metal halides with dry alkali metal salts such as the sulphides, nitrides, phosphides, arsenides etc. to give exchange of anions. They tend to be very exothermic with higher valence halides and are frequently initiated by mild warming or grinding. Metathesis is described as a controlled explosion. Mixtures considered in the specific reference above include lithium nitride with tantalum pentachloride, titanium tetrachloride and vanadium tetrachloride, also barium nitride with manganese II iodide, the last reaction photographically illustrated. 

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