Grey arsenic

Synonyms and Compounds Grey arsenic metallic arsenic arsenic trichloride arsenic trioxide arsenic salts... 

The ionisation potential for electrons in arsenic vapour has been calculated to be 9-04 volts 3 the value previously accepted was 11-54 volts.4 The inelastic collision potential is 4-69 volts, and the resonance potential 4-7 volts.5 The electrical conductivity of metallic arsenic at 0° C. is 0-00285 mho.6 The yellow and amorphous forms do not conduct electricity appreciably. The specific resistance of grey arsenic has been determined 7 at various temperatures as follows ... 

SYNS ARSEN (GERMAN, POLISH) OARSENIC, metallic pOT) ARSENIC BLACK ARSENIC-75 ARSENICALS COLLOIDAL ARSENIC GREY ARSENIC METALUC ARSENIC... 

Synonyms Arsen Arsenic black Arsenic-75 Arsenicals Colloidal arsenic Gray or grey arsenic Metallic arsenic... 

SYNONYMS arsen, Fowler s solution, grey arsenic, colloidal arsenic... 

The substitution of As for P in any compound with P-P linkages is possible, at least in principle. Amongst the simplest known examples are white phosphorus derivatives P4. As , the black phosphorus derivative AsP, AS2P and the mixed sulphides P4. tAS tS3 (Chapter 4.3). Grey arsenic and black phosphorus have been reported as forming limited solid solutions, but the composition P20AS is believed to consist of ordered chains of P atoms as in Hittorf s phosphorus. The As atoms occupy special positions which allow them to link these adjacent chains. 

Three allotrope modifications are known. The stable form is the grey metallic modification with a sublimation temperature of 613°C. Melting is possible in closed tubes at 817°C and a pressure of 28 bar. The metallic allotrope exists in a crystalline (specific weight 5.73 g/cm ) and an amorphous form (specific weight 4.7-5.1 g/cm. The yellow crystalline and the black amorphous modifications are metastable and transform into the grey arsenic under the influence of light or heat. Arsenic is nontoxic in its elementary form [1-5]. 

Arsenic and antimony resemble phosphorus in having several allotropic modifications. Both have an unstable yellow allotrope. These allotropes can be obtained by rapid condensation of the vapours which presumably, like phosphorus vapour, contain AS4 and Sb4 molecules respectively. No such yellow allotrope is known for bismuth. The ordinary form of arsenic, stable at room temperature, is a grey metallic-looking brittle solid which has some power to conduct. Under ordinary conditions antimony and bismuth are silvery white and reddish white metallic elements respectively. 

Arsenic. The presence of arsenie in an organie eompound is generally revealed by the formation of a dull grey mirror of arsenic on the walls of the test-tube when the eompound is fused with sodium in the Lassaigne teat. Usually sufficient arsenic is found in the fusion solution to give a yellow precipitate of arsenic trisulphide when the solution is acidified with hydrochloric acid and treated with hydrogen sulphide. 

Arsenic exists as grey, yellow and black forms of differing physical properties and susceptibilities towards atmospheric oxygen. The general chemistry is similar to that of phosphorus but whereas phosphorus is non-metallic, the common form of arsenic is metallic. Traces of arsenides may be present in metallic residues and drosses these may yield highly toxic arsine, ASH3, with water. 

Taylor, D., B.G. Maddock, and G. Mance. 1985. The acute toxicity of nine grey list metals (arsenic, boron, chromium, copper, lead, nickel, tin, vanadium and zinc) to two marine fish species dab (Limanda limanda) and grey mullet (Chelon labrosus). Aquat. Toxicol. 7 135-144. 

Fig. 3. Local structure of Phase-4 showing an arsenate tetrahedron (black) surrounded by 5 Fe06 octahedra (grey) at 3.34 0.09 A and 5 arsenate tetrahedra at 4.35 0.23 A. 

FIGURE 1.36 (a) The unit cell of nickel arsenide, NiAs. (For undistorted hep c/a=1.633, but this ratio is found to vary considerably.) Ni, blue spheres As, grey spheres, (b) The trigonal prismatic coordination of arsenic in NiAs. 

Arsenic, fused with silver, forms an alloy composed of 100 silver and 16 arsenic. It is grey, brittle, granular, and by long fusion great part of the arsenic volatilizes. It may be entirely got rid of by roasting. 

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