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The naturally-occurring mineral contains roughly 43.9% nickel and 56.1% arsenic by mass, but composition of the mineral may vary slightly. [2] Small quantities of sulfur, iron and cobalt are usually present, and sometimes the arsenic is largely replaced by antimony. This last forms an isomorphous series with breithauptite (nickel antimonide).
Arsenic (33 As) has 32 known isotopes and at least 10 isomers. Only one of these isotopes, 75 As, is stable; as such, it is considered a monoisotopic element . The longest-lived radioisotope is 73 As with a half-life of 80 days.
Typical background concentrations of arsenic do not exceed 3 ng/m 3 in the atmosphere; 100 mg/kg in soil; 400 μg/kg in vegetation; 10 μg/L in freshwater and 1.5 μg/L in seawater. [49] Arsenic is the 22nd most abundant element in seawater [ 50 ] and ranks 41st in abundance in the universe.
When administered intravenously, a steady state is reached after 8–10 days. Arsenic binds to proteins to an insignificant extent. The highest concentrations of arsenic are found in the liver, kidneys, heart, lungs, hair, and nails. Arsenous acid is oxidized to arsenic acid and methylated in the liver, [65] [66] [67] and then excreted 60% in ...
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.
Inorganic arsenic and its compounds, upon entering the food chain, are progressively metabolized to a less toxic form of arsenic through a process of methylation. [7] Organoarsenic compounds arise via biomethylation of inorganic arsenic compounds, [8] via processes mediated by enzymes related to vitamin B 12. [9]
Arsenic (III) enters the cells though aquaporins 7 and 9, which is a type of aquaglyceroporin. [26] Arsenic (V) compounds use phosphate transporters to enter cells. [26] The arsenic (V) can be converted to arsenic (III) by the enzyme purine nucleoside phosphorylase. [26]
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]