Rhodium trichloride, also known as rhodium chloride, is a kind of red-brown powder, easy to deliquescence. Toxic! Molecular weight 209.26 (anhydrous), melting point 450-500 ("decomposition"). Boiling point 800 ("sublimation"). Polyfluorides are formed at temperatures above 600 C. It can be reduced by hydrogen at 70 C. It is insoluble in water, acid and aqua regia, and in methanol and cyanide solutions. In concentrated acid (nitric acid, sulfuric acid) heating decomposition. When heated, it can react with sodium, aluminum, magnesium, iron and other metals. Method: Rhodium is prepared by the reaction of rhodium with chlorine or rhodium oxide with hydrogen chloride at 400 - 600 C. Used in electronics, instrumentation, metallurgy and other industries, also used in plating operations, catalyst preparation.
Rhodium trichloride is prepared by grinding sponge rhodium and potassium chloride with molar ratio of 1:2, then heating in chlorine gas at 550 C for 60 minutes, soaking red products with water, filtering, containing K2 [Rh (H2O) Cl5] in the filtrate, adding sufficient amount of potassium hydroxide solution, precipitating rhodium hydroxide (III) (rhodium trioxide hydrate). After washing and precipitation, the precipitation is dissolved in as little hydrochloric acid as possible, and the evaporation solution is nearly dry, then the wine red RhCl3.3H2O crystal can be obtained. By recrystallizing the crystal in concentrated hydrochloric acid and removing nitrogen impurities, a relatively pure rhodium trichloride trihydrate can be obtained.
At 200-300 degree C, chlorine reacts with rhodium to form a red RhCl3 crystal, which is insoluble in water. RhCl 3.3H 2 O 2 was heated to 180 C in a dry hydrogen chloride gas stream to obtain water soluble RhCl 3. In the former reaction, if molten sodium chloride is used as the medium, the reaction product is Na3RhCl6.
Rhodium trichloride is usually slightly harmful to water bodies. Do not expose undiluted or large quantities of products to groundwater, waterways or sewage systems. Do not discharge materials into the surrounding environment without government permission.