Rhodium is a rare transition metal that has a bright silvery white color in its natural solid state. It is known for its strength and hardness, as well as its high reflecting characteristics. Rhodium has an atomic weight of 102.90550, a melting point of 3567 °F, and a boiling point of 6683 °F. Common uses of rhodium include: as a component in platinum and palladium alloys to strengthen the alloy, as a component in electrical contact material, plating for use in optical instruments, and as a component in some jewelry.
Rhodium is only present in nature in very small amounts in ores that contain metals such as palladium, platinum, silver, and gold. Isolation of rhodium is very complex.
The complexity of rhodium isolation is due to the many metals that it occurs with in nature. Separating rhodium from these metals is a multi-step process. The first step to rhodium isolation involves treating the ore it is present in to take out any silver, gold, palladium, or platinum. The remaining ore is then treated with sodium bisulphate and melted. Next, the melted mixture is extracted with water resulting in rhodium sulfate in solution. The rhodium sulfate is then precipitated out in hydroxide form through a reaction with sodium hydroxide. The next step of the isolation process involves dissolving the hydroxide form of rhodium with hydrochloric acid to yield H3RhCl6; this compound is reacted with ammonium chloride and sodium nitrite to from a precipitate of rhodium. The addition of hydrochloric acid dissolves the precipitate. Pure rhodium is extracted from the precipitate solution using hydrogen gas to burn off and evaporate contaminants.
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