Lead arsenides

Blei, n. lead, -abgang, m. lead dross, lead scoria, -ablagerung,/. lead deposit, -acetat, n. lead acetate, -ader, /. lead vein, -anti-monerz, n., -antimonglanz, m. zinkenite. -arbeit, /. lead smelting plumbing, -arse-nat, n. lead arsenate, -arsenglanz, m. sarto-rite. -arsenik, m. lead arsenate lead arsenide, -art, /. kind or variety of lead. 

Lead Arsenides.—An investigation of the system Pb-As reveals no evidence of the existence of any definite compounds.15 At its melting... 

Lead—antimony or lead—arsenic ahoys must not be mixed with lead—calcium (aluminum) ahoys in the molten state. Addition of lead—calcium—aluminum ahoys to lead—antimony ahoys results in reaction of calcium or aluminum with the antimony and arsenic to form arsenides and antimonides. The dross containing the arsenides and antimonides floats to the surface of the molten lead ahoy and may generate poisonous arsine or stibine if it becomes wet. Care must be taken to prevent mixing of calcium and antimony ahoys and to ensure proper handling of drosses. 

More than 200 ores are known to contain cobalt but only a few are of commercial value. The more important are arsenides and sulfides such as smaltite, C0AS2, cobaltite (or cobalt glance), CoAsS, and linnaeite, C03S4. These are invariably associated with nickel, and often also with copper and lead, and it is usually obtained as a byproduct or coproduct in the recovery of these metals. The world s major sources of cobalt are the African continent and Canada with smaller reserves in Australia and the former USSR. All the platinum metals are generally associated with each other and rhodium and iridium therefore occur wherever the other platinum metals are found. However, the relative proportions of the individual metals are by no means constant and the more important sources of rhodium are the nickel-copper-sulfide ores found in South Africa and in Sudbury, Canada, which contain about 0.1% Rh. Iridium is usually obtained from native osmiridium (Ir 50%) or iridiosmium (Ir 70%) found chiefiy in Alaska as well as South Africa. 

Arsenic and antimony are metalloids. They have been known in the pure state since ancient times because they are easily obtained from their ores (Fig. 15.3). In the elemental state, they are used primarily in the semiconductor industry and in the lead alloys used as electrodes in storage batteries. Gallium arsenide is used in lasers, including the lasers used in CD players. Metallic bismuth, with its large, weakly bonded atoms, has a low melting point and is used in alloys that serve as fire detectors in sprinkler systems the alloy melts when a fire breaks out nearby, and the sprinkler system is activated. Like ice, solid bismuth is less dense than the liquid. As a result, molten bismuth does not shrink when it solidifies in molds, and so it is used to make low-temperature castings. 

The low-melting-point (157 °C), silver metal is mainly used in alloys to decrease the melting point. Combined with tin, lead, and bismuth to produce soldering metal for wide temperature ranges. The element is highly valuable in the electronics age as its unique properties are ideal for solar cells, optoelectronics, and microwave equipment. The arsenide is used in lasers and is also suitable for transistors. ITO (indium tin oxide) is a transparent semiconductor with wide application in displays, touchscreens, etc. In the household, indium as an additive prevents the tarnishing of silverware. Some electronic wristwatches contain indium batteries. 

While most other techniques use a limited amount of detectors (e.g., silica for visible, photomultipliers for UV) and MIR has a small number, NIR uses many types of semiconductors for detectors. The original PbS detectors are still one of the largest used in NIR, however, indium gallium arsenide (InGaAs), indium arsenide (InAs), indium antimonide (InSb), and lead selenide (PbSe) are among the semiconductor combinations used, both cooled and ambient. 

Instead of glowbars, as used in MIR, tungsten halogen lamps are the sources of light. The detectors are solid-state semiconductors such as lead sulfide (PbS) or indium gallium arsenide (InGaAs). These are orders of magnitude quieter than typical MIR detectors and often more sensitive. 

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. 

The reaction of the lithium bis(trimethylsilyl)arsenide (47) with -butyl phosphaethyne (45) <89TH 423-01,93PS(77)45,94JOM(480)45> or a phosphaalkene precursor thereof (46) leads to a mixture of lithium 1,2,4-triphospholide, 1,2,4-diphosphaarsolide (48) and 1,4,2-diphosphaarsolide (49) (Scheme 11). 

Arsenic occurs also in a great variety of other minerals, generally as mixed arsenides and sulphides of the heavy metals or as metallic arsenites and arsenates, anhydrous and hydrated. The more common of these are listed below, with their approximate composition. They are to be found in small quantities widely scattered over Europe,12 Asia, America and Australia. Thus arsenical minerals in great variety13 are found in the blendes and lead glances of the Eastern Alps, the former... 

As mentioned in Chapter II, many metallic arsenides are found in Nature. Arsenic combines directly with most metals to form stable compounds, those of the heavy metals being the most stable. The latter may be obtained by allowing an aqueous solution of a salt of the appropriate metal to drop into an atmosphere of arsine, air being completely absent, and the vessel continually shaken.1 Precipitation by passing arsine into the salt solution is not satisfactory as, in the case of copper, silver, gold, mercury and lead, a secondary reaction with the excess of metallic ions occurs ... 

Arsenic Trifluoride, AsF3, is formed when fluorine reacts with arsenic trichloride 1 or with the arsenides of the alkali or alkaline earth metals 2 by the action of anhydrous hydrofluoric acid or of acid fluorides on arsenious oxide 3 by the action of certain metallic fluorides, for example silver or lead fluoride on arsenic trichloride,4 or of ammonium fluoride on arsenic tribromide B and by the action of iodine pentafluoride on arsenic.6... 

The reaction commences at a temperature above 400° C., before the melting temperature is reached, and the fused product therefore always contains some arsenious oxide.1 When heated in hydrogen, the pentoxide is reduced first to arsenious oxide and then to free arsenic. Similar reduction occurs when it is heated with carbon or phosphorus with sulphur, arsenious sulphide is formed. Arsenic and metallic arsenides result when the pentoxide is heated with alkali metals,2 zinc, lead, iron or most other heavy metals mercury and silver react only at high temperature gold and platinum do not react. 

Typical materials used in NIR photoconductive detectors are PbS, PbSe, InSb and InAs (lead sulphide, lead selenide, indium antimonide and indium arsenide). 

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