Silver compounds geochemistry

Although the abundance of silver in the Earth s crust is comparatively low (0.07 pgg-1), it is considered an environmental contaminant and is toxic at the nanomolar level. As an environmental pollutant it is derived from mining and smelting wastes and, because of its use in the electrical and photographic industries, there are considerable discharges into the aquatic environment. Consequently, there have been studies on the geochemistry and structure of silver-sulfur compounds [31]. Silver, either bound to large molecules or adsorbed on to particles, is found in the colloidal phase in freshwater. In anoxic sediments Ag(I) can bind to amorphous FeS, but dissolved silver compounds are not uncommon. A more detailed study of silver speciation in wastewater effluent, surface and pore waters concluded that 33-35% was colloidal and ca. 15-20% was in the dissolved phases [32]. 

Bell, R.A. and J.R. Kramer. 1999. Structural chemistry and geochemistry of silver-sulfur compounds critical review. Environ. Toxicol. Chem. 18 9-22. 

All other expected relationships of elements or ions may be used in assessing the extent of purification of inorganic substances. Common associations include sodium and potassium calcium, strontium, and barium phosphorus and arsenic arsenic and antimony and iron, cobalt, and nickel. There are a number of less well known but useful associations that are often described in textbooks of geochemistry, including silver with lead and its compounds arsenic with copper and its compounds and manganese in magnesium compounds. 

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