Bismuth, hydrous oxides

Figure 3 Uptake of K+ and Cl by hydrous bismuth oxide. Exchanger, 0.25 g total volume, 12.5 cm ionic strength, 0.1 M (HCl + KCl) or (KOH + KCl), temp. 30°C. (From M. Abe and T. Ito, Nippon Kagaku Zasshi, 85 817 (1965). With permission.)...

Mathur, B.S. and Venkataramani, B., Sorption characteristics of hydrous bismuth-thorium mixed oxides, Indian J. Chem.. 38A, 1092, 1999. 

Consequently, addition of soluble mercury or lead salts or a little hydrous bismuth oxide yields the respective black sulfide. 

This test for lead is interfered with by cerium, manganese, bismuth, cobalt, nickel, silver and thallium salts. Under the same conditions, these metal ions also give higher oxides capable of oxidizing benzidine to benzidine blue. If, however, the lead test is carried out in an alkaline extract (plumbite solution), only thallium offers interference. All the other metal ions are precipitated as hydrous metal oxides and so do not enter the alkaline extract. When only bismuth salts are present, it is sufiftcient, before the addition of bromine water, simply to heat with the alkali, BiO(OH) is formed which is not converted into the higher bismuth oxide by hypobromite. 

---