Figure 13
From: A Raman spectroscopic study of arsenite and thioarsenite species in aqueous solution at 25 °C
Highly schematic diagram showing approximate predominance fields of various As species as a function of pH and ΣS/ΣAs ratio for ΣAs + ΣS = 0.1 mol kg-1 H2O. With the exception of the boundaries between the arsenite species (H3AsO3 0, H2AsO3 -, HAsO3 2-, AsO3 3-), the slopes and the positions of the boundaries are highly uncertain. The letters correspond to species responsible for observed Raman bands as follows: A, 385 cm-1; B, 400 cm-1; C, 420 cm-1; D, 390 cm-1?; E, 330 and 415 cm-1; and F, 385 cm-1. At ΣAs + ΣS = 0.5 mol kg-1 H2O an additional species with a band at 360–370 cm-1 joins species D at pH = 12.6 and intermediate ΣS/ΣAs.