ABSTRACT
Pentavalent antimony in the presence of a large excess of chloride ion (2) reacts with Rhodamine B to form a colored complex, which may be extracted with organic solvents such as benzene, toluene, xylene, or isopropyl ether (2, 3, 4, 5, 6, 7, 8, 9). Trivalent antimony will not react with Rhodamine B and must be oxidized to the pentavalent state, (i.e., Sb2O5) by digestion in sulfuric, nitric, and perchloric acids. Phosphoric acid is used to minimize interference by iron. The absorbance of the pink-colored extract is measured in a spectrophotometer at 565 nm, or in a colorimeter using a green filter, and the amount of antimony present determined by reference to a calibration curve or regression equation prepared from known amounts of antimony.
