Arsenic: the essentials

Elemental arsenic occurs in two solid modifications: yellow, and grey or metallic, with specific gravities of 1.97, and 5.73, respectively. The element is a steel grey, very brittle, crystalline, semimetallic (metalloid) solid. It tarnishes in air, and when heated rapidly oxidises to arsenous oxide which has a garlic odour.

Arsenic and its compounds are poisonous as any reader of "who-done-it" books knows. Upon heating arsenic and some minerals containing arsenic, it sublimes (transfers from the solid to the gaseous state, without passing through the liquid state).

Table: basic information about and classifications of arsenic.

Arsenic: historical information

Arsenic was discovered by Known since ancient times at no data in not known. Origin of name: from the Greek word "arsenikon" meaning "yellow orpiment".

Arsenic compounds were mined by the early Chinese, Greek and Egyptian civilisations. No doubt they discovered its toxic properties early on.

It is believed that Albertus Magnus obtained the element in 1250 A.D. who obtained it by heating soap together with orpiment (arsenic trisulphide, As2S3).

Arsenic is one of the elements which has an alchemical symbol, shown below (alchemy is an ancient pursuit concerned with, for instance, the transformation of other metals into gold).

{{floatR}}alchemical symbol of arsenic{{/floatR}}

Arsenic: physical properties

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Arsenic: orbital properties

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Isolation: it is not usually necessary to make arsenic in the laboratory as it is commercially available. Arsenic is found in nature in a number of minerals including realgar (As4S4), orpiment (As2S3), arsenolite (As2O3), and iron minerals such as arsenopyrite (FeAsS) and loellingite (FeAs2). Arsenic is made on an industrial scale by heating appropriate minerals in the absence of air. The arsenic is condensed out as a solid.

FeAsS (700°C) → FeS + As(g) → As(s)

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arsenic atomic number