Orpiment

Orpiment

Geochemistry of Contaminant Mobility

Published in William J. Deutsch, Groundwater Geochemistry, 2020

Arsenic and selenium form fairly soluble arsenate [As(V)] and selenite [Se(IV)] minerals under oxidizing conditions in combination with iron (FeAsO4, Fe2[OH]4[SeO3]), lead (Pb3[AsO4]2), and manganese (Mn3[AsO4]2). Under reducing conditions, elemental selenium may limit solution concentrations, as well as the iron selenide FeSe2. Arsenic forms very insoluble sulfide minerals such as orpiment (As2S3) under reducing conditions.

Assessing the Impact of LED Lighting on the Stability of Selected Yellow Paint Formulations

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Journal Information

Published in LEUKOS, 2020

Emma Richardson, Elizabeth Woolley, Asya Yurchenko, David Thickett

The discoloration of arsenic sulfide (orpiment) is well documented and known to form the more stable arsenic oxide compound, arsenolite (As2O3), particularly on exposure to wavelengths shorter than 428 nm (Allen et al. 2005). Whitmore and Cass (1989) have also suggested that there may be a link between the presence of nitrogen dioxide and accelerated deterioration of both orpiment (As2S3) and realgar (As4S4). The concentrations of nitrogen dioxide were equivalent inside all three light chambers. Therefore, the measured color shift is likely due to the higher spectral power distribution between 380 and 429 nm in the LED2 lamps.

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Geochemistry of Contaminant Mobility

Assessing the Impact of LED Lighting on the Stability of Selected Yellow Paint Formulations