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It oxidises readily in air to form arsenic trioxide and water, and analogous reactions take place with sulfur and selenium instead of oxygen. [3] 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.
As reported in 1775, Carl Scheele reduced arsenic(III) oxide with zinc in the presence of acid. [11] This reaction is a prelude to the Marsh test. Alternatively, sources of As 3− react with protonic reagents to also produce this gas. Zinc arsenide and sodium arsenide are suitable precursors: [12]
Nitric oxide (NO) reacts with reactive oxygen species to form peroxynitrite. [28] In cases of chronic arsenic exposure, the nitric oxide levels are depleted, due to the superoxide reactions. [28] The enzyme NO synthase (NOS) uses L-arginine to form nitric oxide, but this enzyme is inhibited by monomethylated arsenic (III) compounds. [28]
It burns in oxygen to form arsenic trioxide and arsenic pentoxide, which have the same structure as the more well-known phosphorus compounds, and in fluorine to give arsenic pentafluoride. [31] Arsenic makes arsenic acid with concentrated nitric acid , arsenous acid with dilute nitric acid, and arsenic trioxide with concentrated sulfuric acid ...
Despite the well known toxicity of arsenic, arsenic trioxide was used in traditional Chinese medicine, where it is known as pi-shuang (Chinese: 砒霜; pinyin: pīshuāng; lit. 'arsenic frost'). In homeopathy, it is called arsenicum album. Some discredited patent medicines, e.g., Fowler's solution, contained derivatives of arsenic oxide. [20]
In chemistry, an arsenite is a chemical compound containing an arsenic oxyanion where arsenic has oxidation state +3. Note that in fields that commonly deal with groundwater chemistry, arsenite is used generically to identify soluble As III anions. IUPAC have recommended that arsenite compounds are to be named as arsenate(III), for example ...
Arsenic-arsenic bonds are very weak, and oligomeric arsenic compounds are even more liable to oxidize than their hydrogenated precursors. [6]: 318–320 The following reaction can, however, be prepared through electrochemical reduction in a zinc-sulfate cell. [6]: 473 Oxidation first forms polymeric arsinoxides, e.g.: MeAs + O → MeAsO
Oxyarsenides or arsenide oxides are chemical compounds formally containing the group AsO, with one arsenic and one oxygen atom. The arsenic and oxygen are not bound together as in arsenates or arsenites, instead they make a separate presence bound to the cations (metals), and could be considered as a mixed arsenide-oxide compound.