Introduction Ammonia (NH₃) is a colourless, low molecular weight gas with the chemical formula NH₃ (See figure 1). It has a pungent smell, often associated with strong household cleaners. Ammonia (NH₃) is lighter than air but can be easily condensed to a liquid due to strong hydrogen bonding between the ammonia molecules (hydrogen bonding is…
Where does nickel come from? Pure nickel (Ni) is a silvery-white metal that is rarely found as a pure metal in the earth’s crust because it will oxidise when it comes into contact with oxygen. Pure nickel can be found in the interiors of larger nickel–iron meteorites that were not exposed to oxygen when outside…
Introduction Mercury species exists in various forms: elemental (or metallic); inorganic (e.g. mercuric chloride); and organic mercury (e.g., methyl- and ethylmercury), which all have different toxic effects. Mercury poisoning can result from exposure to water-soluble forms of mercury (such as mercuric chloride or methylmercury), inhalation of mercury vapour, or by ingesting any form of mercury.…
Where does lead come from? Lead is most commonly found as lead (II) sulphide (PbS) in the mineral galenite. Cerussite (tin-lead ore), with the chemical composition lead (II) carbonate (PbCO₃), is a secondary mineral of lead formed by the chemical reaction of carbonated water with galena. A third important source of lead is anglesite (lead…
The “rotten egg” odour in some water supplies is caused by sulphide in water. Sulphide can be treated using oxidation techniques, the goal being to convert the sulphide to high oxidation state species such as sulphate to eliminate the taste and odour concerns. Traditional oxidation techniques such as ozone and chlorine can be used but…
Introduction Arsine (AsH₃) is an extremely toxic gas that is generated upon exposure of arsenic-containing ores to acids. It is also a by-product of refining of non-ferrous metals. Arsine is used extensively in the manufacture of microchips, solid-state lasers and for the synthesis of organoarsenic compounds. Arsine (AsH₃) is a colourless, flammable, non-irritating toxic gas…
Introduction Phosphine is the compound with the chemical formula PH₃. Phosphine (PH₃) is used as an intermediate in organophosphorus chemistry and as a dopant in the semiconductor industry. Phosphine (PH₃) is alsowidely used as a fumigant (for example, in the tobacco industry) that does not leave residues on the stored product, and for pest control.…
