after sample decomposition and recovery of antimony and bismuth retained by lead and calcium sulphates , by co-precipitation with hydrous ferric oxide at ph 6.20 +/- 0.05 , iron ( iii ) is reduced to iron ( ii ) with ascorbic acid , and antimony , bismuth , copper , cadmium and indium are separated from the remaining matrix elements by a single methyl isobutyl ketone extraction of their iodides from ~2m sulphuric acid-0.1m potassium iodide .
C0021966
iodides
C0032831
potassium iodide