Long before its discovery, Arsenic was used for many purposes. It was mentioned in one papyrus as a ways of gilding metals, as it was known to the ancient Egyptian. Theophrastus, a Greek philosopher knew two sulphide metals namely orpiment and realgar. He compiled his great work during the Ming Dynasty. Since ancient times, Arsenic sulphides and oxides have been known. White arsenic, a more dangerous form of Arsenic was a by–product of copper refining. Albertus Magnus first isolated the element in 1250 and later in 1649, Johann Schroeder, a German chemist discovered two methods of preparing Arsenic.
The most common mineral from which Arsenic is obtained is Arsenopyrite, which is an iron arsenic sulphide and is also called mispickel. This mineral sublimes or changes directly to gaseous state without becoming a liquid after heating and the residue left behind is ferrous sulphide. Another mineral, Orpiment is found near the volcanic hot springs.
Some of the important properties of Arsenic are:
- Along with two other allotropes, yellow and black, Arsenic is a crystalline metalloid that is usually steel gray and is very brittle.
- When in contact with air, it begins to tarnish and when heated, it undergoes rapid oxidization into arsenic oxide.
- It has an odour of strong garlic.
- The element and its compounds are poisonous in nature.
Arsenic is mono–isotopic. It is composed of one naturally occurring stable isotope, 75As. According to the details of 2003, about 33 radioisotopes have been synthesized that ranges between the atomic mass from 60–92. The most stable among them is 73As with a half–life of 80.30 days. The remaining isotopes, however, have half–lives of less than a day. Excluding the exceptions, those isotopes that are lighter than 75As tend to decay by beta+ decay whereas those that are heavier tend to decay by beta– decay.
Important uses of Arsenic are:
- It often acts as a doping agent for solid–state devices.
- Electricity is converted into coherent light by Gallium arsenide.
- Its compounds such as Paris green, calcium arsenate and lead arsenate are used as insecticides and other poisons.
- In pyrotechnics, an additional colour is given to the flame by Arsenic.
- The element improves the sphericity of lead shot.
- In history, Arsenic has been used as a poison but is easily detectable.
- Orpiment, an arsenic sulphide known for its bright yellow colour was traditionally used as a poison and a medicine, as well as a pigment for paintings and sealing wax.
Drinking water at the concentrations of 50 ug/litre or even lower can cause cancer in the skin, lungs, bladder and kidney. It may also lead to skin changes such as thickening and pigmentation. Intake of large amounts of Arsenic causes gastrointestinal symptoms such as severe vomiting, disturbances of the blood and circulation, damage to the nervous system and may eventually lead to death. Such large doses, if not deadly may lead to reduced blood cell production, breaking up of the red blood cells in the circulation, enlarging of the liver, colouring of the skin, tingling and loss of sensation in the limbs and brain damage.