Description
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Arsenic is a metalloid that has a metallic grey color in its natural solid state. Arsenic is one of the more well known elements for its highly popularized toxicity. Arsenic has an atomic weight of 74.92160, a melting point of 1503 °F, and a boiling point of 1137 °F. Some common uses of arsenic include: as a wood treating agent for pressure treated wood, as an insecticide, as a component in semiconducting materials, and in the process of bronzing, as a component in pyrotechnics.
Isolation
Arsenic is found in its free form in nature. For commercial purposes, isolation procedures are used to extract arsenic from minerals.
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The mineral that is most commonly used for arsenic isolation purposes is arsenopyrite; this mineral is an iron arsenic sulfide that is associated with gold mining, and on average it is composed of 46% pure arsenic. Orpiment is the second most common arsenic ore; orpiment is a mineral that is composed of arsenic sulfide, but it is not usually used for arsenic isolation.
To isolate arsenic from the mineral arsenopyrite, the mineral is roasted in the absence of air. As the arsenic heats, the iron and arsenic in the mineral are transformed into their oxide counterparts. The temperature of the reaction is approximately 1292 °F. As the reaction proceeds, arsenic gaseous oxide is condensed out as pure arsenic solid; iron sulfide is produced as well. Arsenic is a highly toxic metalloid and in its pure state it can cause a number of health problems including death; pure arsenic must be handled with caution, and it is hardly ever isolated in a laboratory.