Nuclear chemistry

Catalysis

Orthorhombic crystal system

Rhodium

Sulfuric acid

Crystal structure

Decomposition

Inorganic chemistry

Sulfate

Oxidizing agent

Organic chemistry

Thermal decomposition

Analytical Chemistry (journal)

Crystallography

Chemistry

Infrared spectroscopy

European Journal of Inorganic Chemistry

The reaction of elemental rhodium and concentrated sulfuric acid (97 %) at 400 °C leads to red plate‐shaped single crystals of Rh 2 (SO 4 ) 3 [trigonal, R 3 , Z = 6, a = 806.8(1) pm, c = 2204.8(4) pm, V = 1242.8(4) × 10 6 pm 3 ]. The same reaction carried out at a temperature of 475 °C leads to orange crystals of Rh 2 (SO 4 ) 3 · 2H 2 O [orthorhombic, Pnma, Z = 4, a = 920.46(2) pm, b = 1244.47(3) pm, c = 833.37(2) pm, V = 954.61(4) × 10 6 pm 3 ]. Thermal analysis and X‐ray powder diffraction measurements were performed to investigate the decomposition and resulting residues of the compounds. For both compounds the decomposition occurs through two steps and is finished at around 1000 °C at the stage of elemental rhodium. Additionally both sulfates were characterized by means of IR spectroscopy.

Oxidizing Rhodium with Sulfuric Acid: The Sulfates Rh 2 (SO 4 ) 3 and Rh 2 (SO 4 ) 3 ·2H 2 O