Application in the Phase Analysis of Bismuth Ores by Inductively Coupled Plasma Atomic Emission Spectrometry

A portion (0.500 0 g) of bismuth ore was extracted with 0.5 g of ascorbic acid and 50 mL of 1 mol·L^-1 HCl solution by shaking for 30 min, at 25 ℃. After filtration on fine texture filter paper, the filtrate containing bismuth of oxide ore was collected to prepare a testing solution with a volume of 100.0 mL and containing 20% (volume fraction, the same below) by volume of HCl, which was used for inductively coupled plasma atomic emission spectrometry (ICP-AES) determination for its Bi-content. The filter paper containing the insolubles was taken and extracted with 0.5 g of NH₂OH·HCl and 25 mL of 20% HCl solution by heating in a water bath at 100 ℃ for 1 h. After which 25 mL of H₂O were added and the mixture was filtered. The filtrate containing bismuth of bismuthinite was collected and made its volume to 100.0 mL containing 20% by volume of HCl, which was used for ICP-AES determination for its Bi-content. The filter paper with insolubles on it was transferred to a porcelain crucible and ashed for 2 h at 800 ℃. After cooling, the residue in the crucible was dissolved by heating with 20 mL of an acid mixture of HCl-HNO₃-H₂O (3+1+2), and when the solution was concentrated to a volume of ca. 10 mL, 10 mL of HCl (1+1) solution were added and its volume was made up to 50.0 mL with H₂O. The solution was used for determination bismuth of native bismuth ore by AFS. Another portion (0.500 0 g) of the bismuth ore sample was taken and dissolved by heating with 20 mL of the above mentioned mixed acid. When the volume of the solution was reduced to ca. 10 mL during the heating and evaporation, the heating was stopped and 20 mL of HCl (1+1) solution were added to the sample solution and its volume was made up to 100.0 mL, which was used for ICP-AES determination of total bismuth in the ore sample. Linearity range of the standard curve for ICP-AES determination was found within 10.00 mg·L^-1, with detection of bismuth (3S/N) 3.0 μg·g^-1. Three bismuth ore samples were analyzed by the present method and the conventional colorimetric method separately, giving consistent results.