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Nitric oxide (NO) is a part of cell regulation, including cellular metabolism, growth, division and death. [28] 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]
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.
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]
Cacodylic acid, central to arsenic chemistry, arises from the methylation of arsenic(III) oxide. (In contrast, the dimethylphosphonic acid is less significant in the corresponding chemistry of phosphorus.) Phenylarsonic acids can be accessed by the reaction of arsenic acid with anilines, the so-called Bechamp reaction.
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]
In natural waters, the dissolved oxygen content is the main factor influencing reduction potential. Arsenates occur in oxygenated waters, which have a high pe, while arsenites are the main arsenic species in anoxic waters with a low pe. [16] A Pourbaix diagram shows the combined influence of pH and pe on arsenate speciation.
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.