Chemical Properties
White powder. Decomposes to the oxide
at 138C. Soluble in acids and alkalies; insoluble in
water.
Uses
manufacture of beryllium and beryllium oxide.
Physical properties
Beryllium Hydroxide can be prepared by reacting
the oxide with water:
BeO＋H2O→Be(OH)2
If heated, it decomposes at
1273°C. Its solubility in water is slight and its solubility
product Ksp(H2O) is 6.92×10-22. It is soluble in acids and
bases.
Beryllium hydroxide exists in three forms: as a metastable
tetragonal crystalline solid (a-Be(OH)2; as a stable
orthorhombic crystalline solid (b-Be(OH)2); and in
a slightly basic pH, it appears as a slimy, gelatinous
substance (Be(OH)42-).
Definition
beryllium hydroxide: A whitecrystalline compound, Be(OH)2, precipitatedfrom solutions of berylliumsalts by adding alkali. Like the oxide,it is amphoteric and dissolves in excessalkali to give beryllates.
Preparation
Beryllium hydroxide, Be(OH)2, is an amphoteric
hydroxide, dissolving in both acids and alkalis. Industrially
it is produced as a by-product in the extraction of
beryllium metal from the ores, “beryl” and “bertrandite”
When alkali is added to beryllium salt solutions, the
a-form (a gel) is formed. If this left to stand or boiled
the rhombic b-form precipitates. This has the Zn(OH)2
structure with tetrahedral beryllium centers. The alkali
dissolution forms a “beryllate”:
2NaOH(aq)＋Be(OH)2(solid) → Na2Be(OH)4(aq)
With acids, beryllium salts are formed involving the
Be(OH)＋ cation. With sulfuric acid, H2SO4:
2Be(OH)2＋H2SO4→[Be(OH)]2SO4＋ 2H2O
Thus, the probable formula for beryllium hydroxide
is Be(OH)OH. However, this has never been reported.
Beryllium hydroxide dehydrates completely at 400°C to form a white powder of acid soluble beryllium oxide:
Be(OH)2＋ heat → BeO＋H2O
Further heating at higher temperature produces acid
insoluble BeO.
Safety Profile
Confirmed carcinogen withexperimental carcinogenic and tumorigenic data. Poisonby intravenous route. When heated to decomposition it emitsvery toxic fumes of BeO.
