Arsenic

1. What is arsenic?

• 1.1 What are the properties of arsenic?
• 1.2 How are arsenic levels measured?

1.1 What are the properties of arsenic?

Arsenic is a metalloid - a natural element that is not actually a metal but which has some of the properties of a metal. It is a natural component of the Earth’s crust, generally found in trace quantities in all rock, soil, water and air. However, concentrations may be higher in certain areas due to either natural conditions or human activities.

Arsenic can exist in many different chemical forms in combination with other elements. Some forms are inorganic, which do not contain carbon, and others are organic, which always contain carbon. Inorganic arsenic exists in four main chemical forms known as valency or oxidation states. Valency is a measure of the ability of a compound to combine with other elements, such as hydrogen. The dominant forms are arsenite, with a valency of 3, and arsenate, with a valency of 5.

The element arsenic itself is not soluble in water. Arsenic in combination with other elements (as salts) has a wide range of solubilities depending on the surrounding acidity and the presence of other chemicals. More...

1.2 How are arsenic levels measured?

There are various laboratory methods for the detection and measurement of arsenic. Some of these methods can distinguish between the different chemical forms (valency) of the arsenic. Sensitive measuring techniques exist for a limited range of arsenic compounds. A test kit based on a color reaction is currently used for groundwater testing in Bangladesh that is suitable for use under field conditions. More...