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Like all rare-earth metals, cerium is of low to moderate toxicity. [80] A strong reducing agent, it ignites spontaneously in air at 65 to 80 °C. Fumes from cerium fires are toxic. [38] Cerium reacts with water to produce hydrogen gas, and thus cerium fires can only be effectively extinguished using class D dry powder extinguishing media. [81]
Samarium dissolves readily in dilute sulfuric acid to form solutions containing the yellow [22] to pale green Sm(III) ions, which exist as [Sm(OH 2) 9] 3+ complexes: [21] 2Sm (s) + 3H 2 SO 4 (aq) → 2Sm 3+ (aq) + 3SO 2− 4 (aq) + 3H 2 (g) Samarium is one of the few lanthanides with a relatively accessible +2 oxidation state, alongside Eu and ...
The USGS study team has located a sizable area of rocks in the center of an extinct volcano containing light rare-earth elements including cerium and neodymium. It has mapped 1.3 million metric tons of desirable rock, or about ten years of supply at current demand levels. The Pentagon has estimated its value at about $7.4 billion. [185]
Cerium(III) sulfate is one of the few salts whose solubility in water decreases with rising temperature. [12] Ceric ammonium nitrate. Due to ligand-to-metal charge transfer, aqueous cerium(IV) ions are orange-yellow. [13] Aqueous cerium(IV) is metastable in water [14] and is a strong oxidizing agent that oxidizes hydrochloric acid to give ...
Some of the bastnäsites contain OH − instead of F − and receive the name of hydroxylbastnasite. Most bastnäsite is bastnäsite-(Ce), and cerium is by far the most common of the rare earths in this class of minerals. Bastnäsite and the phosphate mineral monazite are the two largest sources of cerium and other rare-earth elements.
Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm 2 O 3 with samarium metal at high temperature (1000 °C) and pressure above 50 kbar; lowering the pressure resulted in incomplete reaction. SmO has cubic rock-salt lattice structure.
Lanthanide metals react exothermically with hydrogen to form LnH 2, dihydrides. [1] With the exception of Eu and Yb, which resemble the Ba and Ca hydrides (non-conducting, transparent salt-like compounds),they form black pyrophoric, conducting compounds [6] where the metal sub-lattice is face centred cubic and the H atoms occupy tetrahedral sites. [1]
A great deal of the lighter lanthanides (lanthanum, cerium, neodymium, and samarium) are formed as fission products. In Africa , at Oklo where the natural nuclear fission reactor operated over a billion years ago, the isotopic mixture of neodymium is not the same as 'normal' neodymium, it has an isotope pattern very similar to the neodymium ...