Promethium compounds

Promethium belongs to the cerium group of lanthanides and is chemically very similar to the neighboring elements.

Even though a few compounds have been synthesized, they are not fully studied; in general, they tend to be pink or red in color.

[3][4] Treatment of acidic solutions containing Pm3+ ions with ammonia results in a gelatinous light-brown sediment of hydroxide, Pm(OH)3, which is insoluble in water.

Cell parameters have been calculated for its octahydrate; they lead to conclusion that the density of Pm2(SO4)3·8 H2O is 2.86 g/cm3.

As-synthesized, e.g. by heating the oxalate, it is a white or lavender-colored powder with disordered structure.