Melting indium compounds

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

In contrast to the non-trivial routes for the syntheses of pure aluminum(I) or gallium(I) subhalides, indium(I) chloride or bromide can simply be prepared by melting mixtures of elemental indium and indium trihalides [39]. When these in-dium(I) halides were treated with bulky alkyllithium compounds, deep violet orga-noelement indium dusters (13-18) were obtained [Eq. (3)] [40, 41]. 

Table 5.64. Highest melting points (°C) in the alloys of aluminium and indium with compound-forming elements of the 4th and 6th rows of the Periodic Table. 

Indium also has many of the characteristics that make Al and Ga very useful for such applications. Particularly important is its capacity to dissolve Si, Ge and several lanthanide and transition metals, producing highly reactive forms of the elements. Moreover In does not form binaries with Si and Ge and has a low-melting point. RNiGe2 compounds, for instance, were prepared from stoichiometric quantities of the components in fine powder mixed with a 10 fold quantity of In in alumina tubes. These, flame sealed in fused silica tubes, were slowly heated to 1000°C, held at this temperature for a few hours, ramped down to 850°C, held for an additional 4 days and finally cooled down to room temperature over the course of another 4 days. Compound isolation from the In excess was performed by centrifugation at 300°C through a coarse frit. Further purification was carried out by a 15-minute submersion and sonication in 6 M aqueous HC1 (Salvador et al. 2004). 

Indiums low melting point is the major factor in determining its commercial importance. This factor makes it ideal for soldering the lead wires to semiconductors and transistors in the electronics industry. The compounds of indium arsenide, indium antimonide, and indium phosphide are used to construct semiconductors that have specialized functions in the electronics industry. 

Reich and Richter found that it is easier to isolate it from the zinc than from the original blende. They reduced indium oxide in a current of hydrogen or illuminating gas and melted the metal under potassium cyanide (44, 45). At the suggestion of Ferdinand Reich, Clemens Winkler made a thorough study of the metal and its compounds (20). 

Renz 4 describes an additive compound of indium trichloride and pyridine, tripyridino-indium trichloride, [In(C5H5N)3]Cl3, which is prepared by adding pyridine to a solution of indium trichloride in alcohol. After standing for a short time, small needle-shaped crystals separate of melting-point 253° C. The compound is not hygroscopic like indium chloride, is somewhat sparingly soluble in alcohol, and is insoluble in ether. It decomposes on warming with water with formation of indium hydroxide, In(OH)3. Aluminium trichloride and iron trichloride form similar addition products. 

Removal of contamination by ion bombardment with inert gas ions, followed by annealing. This method can be applied to either single or poly-crystalline materials and has been found to be effective for the compound indium antimonide having a melting point of 525°C as well as for more refractory materials, ft has also been found to be effective in removing a monolayer of carbon from nickel and silicon crystals. 

The elements of group Illb, gallium, indium, and thallium, are very rare and have small practical importance. Their principal compounds represent oxidation state - -8 thallium also forms thailous compounds, in which it has oxidation number - -1. Gallium is liquid from 29° C. its melting point, to 1700 C, its boiling point. It has found use as the liquid in quartz-tube thermometers, which can be used to above 1200° C. 

Sodium cyclopentadienyl reacts with indium trichloride in ether, tetrahydrofuran, or dioxan, forming the volatile compound InCsHs, which may be obtained as pale yellow needles by sublimation (56). This substance does not melt sharply, but slowly decomposes and darkens at 110°. It is very sensitive to oxidation and is slightly soluble in benzene, in which decomposition takes place it is, however, rather less soluble in ether and petroleiun ether. Water has no action on the compound, but on addition of a little sulfuric acid it is vigorously decomposed. The crystals are slightly sensitive to light. In the preparation of InCsHs an intermediate product, InlCsHsls, can be isolated in very small yield as golden crystals. On sublimation at above 160° it decomposes to form the monocyclopentadienyl compound. 

The metal indium has so far only yielded one derivative, indium diphenyl chloride. This was isolated by the interaction of mercury diphenyl and metallic indium in boiling xylene. It is an insoluble compound, not melting at 350 C. When metallic indium and mercury diphenyl are heated at 270 C. in a nitrogen atmosphere under reduced... 

Indium diphenyl chloride.—Indium trichloride Irom 1-lC grams of metallic indium, and 10-77 grams of mercury diphenyl (3 mols.) are boiled with 50 c.c, of xylene for thirty-seven hours. After filtering, the residue mostly melts at 245" to 250 " C., but a portion does not melt at 295° C. The mass is extracted in a Soxhiet apparatus with dr benzene to remove any mercury compounds, and the residue in the thimble (0 647gram) is organic and found to be indium diphenyl chloride. It is a crystalline, cream-coloured powder, insoluble in the usual organic solvents, and does not melt at 350° C. 

Indium and thallium do not react with tungsten, and no compounds were found. Solubility in the respective metal melt is negligible. 

Indium is a ductile, shiny silver-white metal that may also exist in a black powder form. Indium has an atomic weight of 114.82, an atomic number of 49, and a specific gravity of 7.31 g cm It has a boiling point of 2080 °C, a melting point of 1566°C, and is insoluble in water. The major oxidation states for indium are +1, +2 and +3 valences (Merck Index Online 2002). In aqueous solution, only In(III) is stable, but solid-state compounds with +1 and +2 valences have been isolated (Cotton and Wilkinson 1972). 

In-As System. The phase diagram of the In-As system has been constructed by Liu and Peretti [1]. The system contains a compound which melts congruently at 943 3°C. This compound forms eutectics with the initial components (with indium the eutectic is degenerate). Indium arsenide has the structure of zinc blende with a lattice constant of 6.058A [2]. 

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