Elemental rhodium

The metal is silvery white and at red heat slowly changes in air to the resquioxide. At higher temperatures it converts back to the element. Rhodium has a higher melting point and lower density than platinum. It has a high reflectance and is hard and durable. 

A very active elemental rhodium is obtained by reduction of rhodium chloride with sodium borohydride [27]. Supported rhodium catalysts, usually 5% on carbon or alumina, are especially suited for hydrogenation of aromatic systems [iTj. A mixture of rhodium oxide and platinum oxide was also used for this purpose and proved better than platinum oxide alone [i5, 39]. Unsaturated halides containing vinylic halogens are reduced at the double bond without hydrogenolysis of the halogen [40]. 

Although compounds of the platinum metals are commercially available, many workers, for reasons of economy, prefer to prepare them from the elements. Rhodium, one of the rarest and most expensive of the platinum metals, is not attacked by acids (even aqua regia), and its dissolution in alkaline fusion mixtures (e.g., fused sodium carbonate and potassium nitrate mixtures) or in molten salts (e.g., molten potassium hydrogen sulfate) is inefficient and tedious. Chlorination during heating yields a mixture of water-insoluble chlorides, but in the presence of sodium... 

In the early 1800s, Wollaston received samples of some of these metals. He decided to analyze them. During his work, he found that a sample of platinum ore contained other metals as well. These metals mrned out to be two new elements—rhodium and palladium. The name palladium was taken from Pallas, an asteroid that had been discovered at about the same time. 

The use of elemental rhodium (e.g., rhodium surfaces, rhodium on carbon, rhodium nanoparticles) will not be discussed in this review. 

After the completion of the, s and 4f> states with krypton, a (ifth period commences. As in the fourth period the 55 oibital is mote stable than the or 4J state s and is filled by the elements rubidium and strontium. The occupation of the 4d orbitals commences with die next ( lenient, yttrium and continues normally for the. next ( lenient. Witji niobium however, the spectroscopic data show that one jr electron lias also been transferred to the 4d state, and a single electron occurs in the fp orbital up to the element rhodium, atomic number 45. In the next element, palladium, the remaining electron is also transferred to the 41 state, which is thereby completely filled with ten electrons... 

EINECS 231-125-0 HSDB 2534 Rh Rhodium Rhodium, elemental Rhodium fume Rhodium, metal. Metallic element in the platinum group alloy with platinum for high temperature thermocouples, furnace windings, laborabory crucibles, spinerets for rayon, electrical contacts, jewelry, catalyst, mp = 1966° d = 12.41. Atomergic Chemetals Degussa AG Noah Cham. Sigma-Aldrich Fine Cham. 

SYNONYMS elemental rhodium, rhodium metal. Synonyms of other insoluble rhodium... 

Synonyms/Trade Names Rhodium metal Elemental rhodium... 

Platinum or palladium coated ceramic element (rhodium also for three-way)... 

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