bismuthates

Bismuthates are a class of chemical compounds containing the bismuthyl cation, BiO+ or the bismuth group, BiO2. They are typically formed by the oxidation of bismuth in the presence of oxygen and a base, or by the reaction of bismuth oxides with alkaline materials. The most common and stable bismuthates are those of alkali metals, such as sodium bismuthate (NaBiO3) and potassium bismuthate (KBIO3). These compounds are often insoluble in water and exhibit a range of colors, from white to yellow to orange.

Sodium bismuthate, NaBiO3, is a powerful oxidizing agent and is frequently used in analytical chemistry to detect and quantify the presence of manganese. In the presence of acid, it oxidizes manganese(II) ions to permanganate ions, which have a distinctive purple color that can be measured spectrophotometrically. This reaction is highly sensitive and selective, making sodium bismuthate a valuable reagent for trace manganese analysis. Sodium bismuthate itself is typically prepared by reacting sodium hydroxide, bismuth(III) oxide, and an oxidizing agent like sodium hypochlorite.

Potassium bismuthate, KBIO3, is another strong oxidizing agent, though it is less commonly used than its sodium counterpart. It finds applications in organic synthesis for certain oxidation reactions. The preparation of potassium bismuthate often involves the reaction of potassium hydroxide with bismuth(III) oxide under oxidizing conditions. Other bismuthates, involving heavier alkali metals or alkaline earth metals, can also be synthesized but are generally less stable or more difficult to prepare. Bismuthates are interesting not only for their oxidizing properties but also for the diverse oxidation states that bismuth can exhibit, ranging from +3 to +5 in these compounds.