Arsenic crystalline

This is formed when arsenic burns in air (cf. phosphorus which gives P4O10). It can exist in two crystalline modifications the stable one at room temperature, which also occurs naturally as arsenolite, has an octahedral form. Solid arsenic(III) oxide is easily reduced, for example by heating with charcoal, when arsenic deposits as a black shiny solid on the cooler parts of the tube. 

The element is a steel gray, very brittle, crystalline, semimetallic solid it tarnishes in air, and when heated is rapidly oxidized to arsenous oxide with the odor of garlic. Arsenic and its compounds are poisonous. 

Solid Compounds. The tripositive actinide ions resemble tripositive lanthanide ions in their precipitation reactions (13,14,17,20,22). Tetrapositive actinide ions are similar in this respect to Ce . Thus the duorides and oxalates are insoluble in acid solution, and the nitrates, sulfates, perchlorates, and sulfides are all soluble. The tetrapositive actinide ions form insoluble iodates and various substituted arsenates even in rather strongly acid solution. The MO2 actinide ions can be precipitated as the potassium salt from strong carbonate solutions. In solutions containing a high concentration of sodium and acetate ions, the actinide ions form the insoluble crystalline salt NaM02(02CCH2)3. The hydroxides of all four ionic types are insoluble ... 

Uranium hexafluoride [7783-81-5], UF, is an extremely corrosive, colorless, crystalline soHd, which sublimes with ease at room temperature and atmospheric pressure. The complex can be obtained by multiple routes, ie, fluorination of UF [10049-14-6] with F2, oxidation of UF with O2, or fluorination of UO [1344-58-7] by F2. The hexafluoride is monomeric in nature having an octahedral geometry. UF is soluble in H2O, CCl and other chlorinated hydrocarbons, is insoluble in CS2, and decomposes in alcohols and ethers. The importance of UF in isotopic enrichment and the subsequent apphcations of uranium metal cannot be overstated. The U.S. government has approximately 500,000 t of UF stockpiled for enrichment or quick conversion into nuclear weapons had the need arisen (57). With the change in pohtical tides and the downsizing of the nation s nuclear arsenal, debates over releasing the stockpiles for use in the production of fuel for civiUan nuclear reactors continue. 

Physical properties of a-crystaUine metallic arsenic are given in Table 1. The properties of P-arsenic are not completely defined. The density of P-arsenic is 4700 kg/m it transforms from the amorphous to the crystalline form at 280 °C and the electrical resistivity is reported to be 107 H-cm. 

MetaUic arsenic is stable in dry air, but when exposed to humid air the surface oxidizes, giving a superficial golden bronze tarnish that turns black upon further exposure. The amorphous form is more stable to atmospheric oxidation. Upon heating in air, both forms sublime and the vapor oxidizes to arsenic trioxide [1327-53-3] AS2O2. Although As O represents its crystalline makeup, the oxide is more commonly referred to as arsenic trioxide. A persistent garliclike odor is noted during oxidation. 

Other Arsenic Compounds. Arsenic trisulfate [65496-42-6] As2(S0 2 he formed by the treatment of arsenic trioxide with SO at 100°C. Arsenyl sulfate [65423-91-8] (As0)2S04, an easily hydroly2ed, hygroscopic crystalline compound, is formed when arsenic trioxide is dissolved in concentrated sulfuric acid. Arsenic triacetate [5128-94-9] As(C2H202)3, mp 82°C, bp 165—170°C, is easily hydroly2ed to a mixture of arsenous and acetic acids. 

Carcinogenic hazard of wood dusts. Carcinogenicity of crystalline silica Inorganic arsenic compounds... 

Although most of the macrocycles that contain phosphorus or arsenic which have thus far been prepared, are primarily transition metals binders, two compounds have been prepared which are essentially crown ethers containing phosphorus. Kudrya, Shtepanek and Kirsanovhave prepared two compounds which are essentially polyoxygen macrocycles but which contain one or two methylphosphonic acid esters as part of the ring. These two macrocycles are shown below as 7d and 17 and are both prepared by the reaction of 2,2 [oxybis(ethyleneoxy)] bisphenolate with methylphosphonic dichloride in a mixture of acetonitrile and benzene. The crystalline monomer 16) and dimer 17) were isolated in 17% and 11% yields respectively as indicated in Eq. (6.13). 

Compound 118. A material recrystallized from methanol and melting at 100-102° is satisfactory. A sample of crystalline Compound 118 may be obtained from Julius Hyman Company, Rocky Mountain Arsenal, Denver, Colo. 

In ultra pure crystalline silicon, there are no extra electrons in the lattice that can conduct an electric current. If however, the silicon becomes contaminated with arsenic atoms, then there will be one additional electron added to the silicon crystal lattice for each arsenic atom that is introduced. Upon heating, some of those "extra electrons will be promoted into the conduction band of the solid. The electrons that end up in the conduction band are able to move freely through the structure. In other words, the arsenic atoms increase the conductivity of the solid by providing additional electrons that can carry a current when they are promoted into the conduction band by thermal excitation. Thus, by virtue of having extra electrons in the lattice, silicon contaminated with arsenic will exhibit greater electrical conductance than pure silicon at elevated temperatures. 

Firing experiments induced thermal transformations on the ochre-precipitates. From these experiments, hematite and a well crystalline arsenate resulted. This indicates that arsenic may be scavenged by an arsenic-rich compound, freshly formed during the initial stages of the water treatment. This is in agreement with the results obtained by Jia Demopoulos (2008), when performing aging tests on solids precipitated from As(V)-Fe(lll) solutions. 

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