Arsenic v Compounds

Two series of compounds of arsenic are common that of arsenic(III) and arsenic(V). Arsenic(III) compounds can be derived from the amphoteric arsenic trioxide As203, which yields salts both with strong acids (e.g. arsenic(III) chloride, AsC13), and with strong bases (e.g. sodium arsenite, Na3As03). In strongly acidic solutions therefore the arsenic(III) ion As3+ is stable. In strongly basic solutions the arsenite ion, AsO is the stable one. Arsenic(V) compounds... 

The discoverj( of the stereoselective biomethylation of a prochiral arsinic acid by a microorganism opens up an exdting new route to optically active tertiary arsines. Numerous microorganisms reductively methylate arsenic(V) compounds . The biological synthesis of (+)-126 by Scopulariopsis brevicaulis was described in 1936. At that time, however, it was not recognized that simple tertiary arsines chiral at arsenic were configurationally stable and amenable to optical resolution. 

The arsenic(V) compounds R3As=NH on thermolysis retain the nitrogen ligand ... 

Chloranil oxidized a variety of methylarsenic(iii) esters, amides, or cyclic thioesters, products such as (89), for example, being obtained from a dithioester of methylarsonous acid. ° The analogous reaction with 2-iodo-l,3,2-dihetero-arsolans, however, proceeded with simultaneous cleavage of the As—I bond and formation of the spirocyclic arsenic(v) compound (90). The six-co-ordinate arsenic(v) anions (91) were produced by addition of an alcohol or phenol to an arsolan in the presence of triethylamine, the latter abstracting a proton and forming the required cation. ... 

Arsenic V) oxide, AS2O5, is a rather indefinite compound (AS2O3 plus cone. HNO3) which loses O2 and forms arsenates(V) with alkalis. 

On concentrating the solution, a solid of formula As40jq. SH O (which may be composed by hydrated arsenic(V) acid) is obtained, and this, on fairly prolonged heating to 800 K, loses water and leaves arsenic(V) oxide. No compounds corresponding to the other acids of phosphorus are formed, but salts are known. 

Arsenic from the decomposition of high purity arsine gas may be used to produce epitaxial layers of III—V compounds, such as Tn As, GaAs, AlAs, etc, and as an n-ty e dopant in the production of germanium and silicon semiconductor devices. A group of low melting glasses based on the use of high purity arsenic (24—27) were developed for semiconductor and infrared appHcations. 

Inorganic ar senic normally occurs in two oxidation states As(V) and As(III). Arsenic (V) gives a significantly lower response than ar senic (III). For pre-reduction As(V) to the As(III) concentrated hydrochloric acid and potassium iodide/ascorbic acid reagents were used. As organoarsenic compounds do not react with sodium tetrahydi oborate, they were decomposed with a mixture of HNO and on a hot plate. 

The in-V compounds combine the elements of Group HI (aluminum, gallium, indium) with those of Group V (phosphorus, arsenic, antimony, bismuth). As can be imagined, a wide variety of compounds can be produced which, in addition to the binary materials, also include ternary and even quaternary materials. 

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. 

Brannon and Patrick [129] reported on the transformation and fixation of arsenic V in anaerobic sediment, the long term release of natural and added arsenic, and sediment properties which affected the mobilization of arsenic V, arsenic III and organic arsenic. Arsenic in sediments was determined by extraction with various solvents according to conventional methods. Added arsenic was associated with iron and aluminium compounds. Addition of arsenic V prior to anaerobic incubation resulted in accumulation of arsenic III and organic arsenic in the interstitial water and the exchangeable phases of the anaerobic sediments. Mobilization of... 

Arsenic triiodide, preparation of, 7 15 Arsenic(V), C-containing compounds, 28 204-216... 

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