Arsenic Ubiquity

The ubiquity of arsenic compounds, disseminated in small quantities both in minerals and in the organic world, has long been recognised. In recent years, so much white arsenic has been isolated as a by-product during the extraction of gold, silver, copper and other metals, that a curious situation has arisen, in that the supplies available considerably exceed the present world requirements. Thus it behoves the chemist to find new directions in which arsenicals may usefully be employed. That some success has already been attained is indicated in these pages. At present the most important application is the widespread use of arsenates in insecticidal dusts and sprays, which are employed to combat the pests which attack fruit and crops of all kinds. The many organic arsenicals which are of therapeutic value are described in another volume of this series. 

Native Arsenic—Compounds of Arsenic—Tables of Minerals Containing Arsenic —The Ubiquity of Arsenic. 

The detection limits of the old methods for the determination of arsenic (10) were too high to determine arsenic in uncontaminated biological samples. With the invention of instrumental techniques, such as flame atomic absorption (emission) spectrometry, graphite furnace atomic absorption spectrometry, neutron activation analysis, inductively coupled plasma atomic emission spectrometry, and inductively coupled plasma mass spectrometry, the ubiquity of arsenic in our environment was proven. The improvement of the analytical techniques has changed the reputation of arsenic from a poisonous substance to an essential trace element at least for warm-blooded animals (11). An arsenic requirement for humans cannot be deduced from these animal experiments. In recent literature, there are certainly more hints that arsenic might be an essential trace element for humans, but there is still a lot of future research work necessary to prove this. 

The ubiquity of water and metals that are ever present in the water means that hydrolysis reactions are essential aspects of many areas of science, industry and nature. Hydrolysis is an important component in water purification and treatment. In water treatment, many metals are removed from solution by precipitation as solid hydroxide phases which, in turn, may remove other metals and metalloids via adsorption onto the formed solids. In many countries, arsenic is removed from groundwater recovered for drinking via adsorption onto solid iron hydroxide, and knowledge ofthe precipitation behaviour of magnesium hydroxide is important in thermal desalination processes. 

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