Lanthanum hydroxide

Lanthanum hydroxide is, a hydroxide of the rare-earth element lanthanum.

Synthesis
Lanthanum hydroxide can be obtained by adding an alkali such as ammonia to aqueous solutions of lanthanum salts such as lanthanum nitrate. This produces a gel-like precipitate that can then be dried in air.


 * La(NO3)3 + 3 NH4OH -> La(OH)3 + 3 NH4NO3

Alternatively, it can be produced by hydration reaction (addition of water) to lanthanum oxide.


 * La2O3 + 3 H2O -> 2 La(OH)3

Characteristics
Lanthanum hydroxide does not react much with alkaline substances, however is slightly soluble in acidic solution. In temperatures above 330 °C it decomposes into lanthanum oxide hydroxide (LaOOH), which upon further heating decomposes into lanthanum oxide (La2O3):


 * La(OH)3 $$\mathrm{ \xrightarrow [-H_2O]{330\ ^{o}C} \ }$$ LaOOH


 * 2 LaOOH $$\mathrm{\xrightarrow [-H_2O]{\Delta} \ }$$ La2O3

Lanthanum hydroxide crystallizes in the hexagonal crystal system. Each lanthanum ion in the crystal structure is surrounded by nine hydroxide ions in a tricapped trigonal prism.