Silver arsenides

Arsen-saure, /, arsenic acid, -silber, n, silver arsenide, -silberblende,/, proustite, -spiegel, m. arsenic mirror, -suifid, n, arsenic sulfide, esp. the pentasulfide. -sulfur, n. arsenic trisulfide, arsenic(III) sulfide, -iir, n, (-ous) arsenide, -verbindung, /. arsenic compound, -vergiftung, /. arsenic poisoning, -wasser-stoff, m. arsenic hydride, arseniuretted hydrogen (specif, arsine, AsHa). -zink, n. zinc arsenide. 

Silver Arsenides.—A study of the system Ag-As gives no evidence of the existence of any definite compound of the two elements.10 When the mixtures were heated in sealed tubes it was observed that the addition of silver lowered the melting point of arsenic to a eutectic point... 

Monolayers can be transferred onto many different substrates. Most LB depositions have been perfonned onto hydrophilic substrates, where monolayers are transferred when pulling tire substrate out from tire subphase. Transparent hydrophilic substrates such as glass [18,19] or quartz [20] allow spectra to be recorded in transmission mode. Examples of otlier hydrophilic substrates are aluminium [21, 22, 23 and 24], cliromium [9, 25] or tin [26], all in their oxidized state. The substrate most often used today is silicon wafer. Gold does not establish an oxide layer and is tlierefore used chiefly for reflection studies. Also used are silver [27], gallium arsenide [27, 28] or cadmium telluride wafer [28] following special treatment. 

Cobalt is the thirtieth most abundant element on earth and comprises approximately 0.0025% of the earth s cmst (3). It occurs in mineral form as arsenides, sulfides, and oxides trace amounts are also found in other minerals of nickel and iron as substitute ions (4). Cobalt minerals are commonly associated with ores of nickel, iron, silver, bismuth, copper, manganese, antimony, and 2iac. Table 1 Hsts the principal cobalt minerals and some corresponding properties. A complete listing of cobalt minerals is given ia Reference 4. 

In Moroccan deposits, cobalt occurs with nickel in the forms of smaltite, skuttemdite, and safflorite. In Canadian deposits, cobalt occurs with silver and bismuth. Smaltite, cobaltite, erythrite, safflorite, linnaeite, and skuttemdite have been identified as occurring in these deposits. AustraUan deposits are associated with nickel, copper, manganese, silver, bismuth, chromium, and tungsten. In these reserves, cobalt occurs as sulfides, arsenides, and oxides. 

Silver(I) phosphide or arsenide complexes have been synthesized. The reaction of AgCl with Ph2PTMS in the presence of a tertiary phosphine gives polynuclear complexes such as... 

Soft, silver white metal that melts in the hand (29.8 °C) and remains liquid up to 2204 °C (difference 2174 °C, suitable for special thermometers). Gallium is quite widespread, but always in small amounts in admixtures. Its "career" took off with the advent of semiconductors. Ga arsenide and Ga phosphide, which are preferential to silicon in some applications, have extensive uses in microchips, diodes, lasers, and microwaves. The element is found in every mobile phone and computer. Ga nitride (GaN) is used in UV LEDs (ultraviolet light-emitting diodes). In this manner, a curiosity was transformed into a high-tech speciality. 

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. 

Arsine reacts with cupric chloride solution to give cupric arsenide. Oxidation with stannic chloride, SnCR, forms hydrogen diarsenide, AS4H2. It reacts with dilute silver nitrate solution forming metallic silver. 

When heated under ordinary pressure, arsenic does not melt the metallic form volatilises at a dull red heat, while amorphous arsenic does so at a lower temperature. The sublimation temperatures are given on p. 32. Even at ordinary temperature the element possesses an appreciable vapour pressure, as may be shown 8 by enclosing pieces of arsenic and silver in a vessel, but not in contact with each other after some months the silver is found to be coated with a film of arsenide. Vapour pressure measurements of grey metallic arsenic and its liquid at temperatures up to 853° C. have been made the results, expressed in atmospheres, are as follows ... 

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 ... 

It forms silver-white, rhombic crystals,7 of density 7-83, and melting point 1020° C. according to Hilpert and Dieckmann8 or 1031° C. according to Friedrich.9 It is non-magnetic. Steel-grey crystals of the arsenide of density 7-94 have been found associated with tin sulphide in the hearth of an old tin smelting furnace in Cornwall.10... 

The yellow substance produced with more concentrated solutions is silver nitrato-arsenide,3 Ag3As.3AgN03, which is formed thus ... 

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. 

Chemical Properties.—Arsenic trisulphide may be reduced to arsenic by heating in a stream of hydrogen the arsenic sublimes. The reaction begins at about 300° C.,10 but proceeds more readily if the sulphide is first fused with an alkali carbonate.11 A similar reduction occurs when the sulphide is heated with a mixture of charcoal and alkali carbonate12 or lime when heated with potassium cyanide,13 an oxalate14 or with a metal such as silver or iron the latter if in excess yields arsenide. 

NICKELINE. A nickel arsenide mineral, NiAs, crystallizes in the hexagonal system but is usually found massive. Color, light copper hardness, 5.0-5.5 specific gravity, 7.784 luster, metallic opaque. Found in several European localities and in the Province of Ontario, Canada in die United States at Franklin, New Jersey, and Silver Cliff, Colorado. It is an ore of nickel. 

The phosphides, arsenides, and antimonides of the other metals are usually dark-coloured substances, with more or less metallic lustre, and therefore conductors of electricity. Some of them occur native for example, smaltine, CoAs2, a common ore of cobalt, forming silver-white crystals copper-nickel, NiAs, red lustrous crystals, and one of the chief nickel ores speiss, a deposit formed in the pots in which smaltine and copper-nickel are fused with potassium carbonate and silica, in the preparation of smalt, a blue glass containing cobalt its formula appears to be Ni8As2. Mispickel, or arsenical pyrites, is a white lustrous substance, of the formula FeSAs. 

Cobalt District, Ontario, Canada, contains the most important ores of cobalt in the form of arsenides, associated with nickel and silver, the last-named metal rendering the ores very valuable. Their cobalt content ranges from 9 to 18 per cent. 

The ore is crushed and ground in.ball mills to pass through a 30-mesh sieve. It is mixed with suitable fluxes (limestone and quartz) and smelted in small blast-furnaces having a capacity of 25 to 30 tons per twenty-four hours. The products obtained are (i) flue dust, which is returned to the furnaces, and crude arsenious oxide, which is resublimed and sold (ii) a silicate slag, which is thrown away unless it contains more than 10 ounces of silver per ton (iii) crude silver bullion, which is mechanically detached and cupelled to a fineness of 994 before it is sold to silver refiners and (iv) a speiss of cobalt, nickel, iron, and copper arsenides, containing considerable amounts of silver. The crude silver bullion contains about three-fourths of the silver present in the ore. 

Temiskamite, Ni4As8, is a silver-white mineral, with a tinge of red, which rdpidly tarnishes. Hardness 5-5 density 7-901. It is found in calcite veins in Ontario.2 Possibly this mineral is the same as Maucherite, a nickel arsenide found in Thuringia.3 The diarsenide chloanthite or white... 

As obtained by these methods, iron mon-arsenide is a silver-white crystalline substance, of density 7-83, and melting at 1020° C. It is non-magnetic. 

In a further method the sample is heated in a sealed tube for 5 min with a mixture (3 + 1) of magnesium and magnesium oxide, which converts all the arsenic into magnesium arsenide On decomposition by dilute sulphuric acid, arsine is evolved and is absorbed in a 0.5% solution of silver diethyldithiocarbamate (AgDDC) in pyridine. The colour produced has an absorption maximum at 560 nm and is proportional to concentration up to 20 fig of arsenic in 3 ml of solution. Alternatively, the arsine is oxidized by bromine and determined iodimetrically. 

Gallium arsenide is also used to make transistors. A transistor is a device used to control the flow of electricity in a circuit. Gallium arsenide has many of the properties of a semiconductor. A semiconductor is a material that conducts an electrical current, but not as well as a metal, such as silver or copper. 

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