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The biogeochemistry of arsenic is complex and includes various adsorption and desorption processes. The toxicity of arsenic is connected to its solubility and is affected by pH. Arsenite (AsO 3− 3) is more soluble than arsenate (AsO 3− 4) and is more toxic; however, at a lower pH, arsenate becomes more mobile and toxic. It was found that ...
In its standard state arsine is a colorless, denser-than-air gas that is slightly soluble in water (2% at 20 °C) [1] and in many organic solvents as well. [citation needed] Arsine itself is odorless, [5] but it oxidizes in air and this creates a slight garlic or fish-like scent when the compound is present above 0.5 ppm. [6]
Arsenic acid or arsoric acid is the chemical compound with the formula H 3 AsO 4. More descriptively written as AsO(OH) 3 , this colorless acid is the arsenic analogue of phosphoric acid . Arsenate and phosphate salts behave very similarly.
Arsenic forms colorless, odorless, crystalline oxides As 2 O 3 ("white arsenic") and As 2 O 5 which are hygroscopic and readily soluble in water to form acidic solutions. Arsenic(V) acid is a weak acid and the salts are called arsenates , [ 5 ] the most common arsenic contamination of groundwater , and a problem that affects many people.
The tables below provides information on the variation of solubility of different substances (mostly inorganic compounds) in water with temperature, at one atmosphere pressure. Units of solubility are given in grams of substance per 100 millilitres of water (g/(100 mL)), unless shown otherwise. The substances are listed in alphabetical order.
Arsenate is the major arsenic form in oxidizing environments; however, in one study, bacteria from arsenic-contaminated soil at a smelter site was able to reduce As(+5) to As(+3) under anaerobic conditions at arsenic concentration as high as 75 mg/L. [3] Arsenate-respiring bacteria and Archaea have also recently been isolated from a diversity of natural environments, including freshwater ...
The compound can be obtained by neutralizing arsenic acid: H 3 AsO 4 + 3 NaOH → Na 3 AsO 4 + 3 H 2 O. The salt (as its dodecahydrate) is isomorphous with trisodium phosphate. [3] The anion AsO 4 3-exists at high pH, but below pH 11.5, it converts to HAsO 4 2-(also written HOAsO 3 2-).
As(OH) 3 is a pyramidal molecule consisting of three hydroxyl groups bonded to arsenic. The 1 H NMR spectrum of arsenous acid solutions consists of a single signal consistent with the molecule's high symmetry. [3] In contrast, the nominally related phosphorous acid H 3 PO 3 adopts the structure HPO(OH) 2.