Chemical elements
  Barium
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
      Barium Hydride
      Barium Subfluoride
      Barium Fluoride
      Acid Barium Fluoride
      Barium Subchloride
      Barium Chloride
      Barium Bromide
      Barium Perbromides
      Barium Iodide
      Barium Periodides
      Barium Mixed Halides
      Barium Mixed Perhalides
      Barium Oxychloride
      Barium Hypochlorite
      Barium Chlorite
      Barium Chlorate
      Barium Perchlorate
      Barium Oxybromide
      Barium Hypobromite
      Barium Bromate
      Barium Perbromate
      Barium Oxyiodide
      Barium Iodate
      Barium Periodate
      Barium Manganites
      Barium Manganate
      Barium Permanganate
      Barium Suboxide
      Barium Oxide
      Barium Hydroxide
      Barium Peroxide
      Barium Peroxyhydrate
      Barium Tetroxide
      Barium Sulphide
      Barium Hydrosulphide
      Barium Polysulphides
      Barium Hydroxyhydrosulphide
      Barium Oxysulphides
      Barium Sulphite
      Barium Thiosulphate
      Barium Dithionate
      Barium Trithionate
      Barium Tetrathionate
      Barium Pentathionate
      Barium Sulphate
      Acid Barium Sulphates
      Barium Pyrosulphate
      Barium Persulphate
      Barium Selenide
      Barium Selenite
      Barium Selenate
      Acid Barium Selenate
      Barium Telluride
      Barium Tellurite
      Barium Tellurate
      Barium Chromite
      Barium Chromate
      Barium Dichromate
      Barium Potassium Trichromate
      Barium Chlorochromate
      Barium Perchromate
      Barium Molybdate
      Barium Permolybdate
      Barium Tungstate
      Barium Uranate
      Barium Diuranate
      Barium Peruranate
      Barium Nitride
      Barium Azide
      Barium Hexammoniate
      Barium Ammonium
      Barium Amide
      Baramide
      Barium Amidosulphonate
      Barium Imide
      Barium Imidosulphonate
      Barium Hyponitrite
      Barium Nitroxysulphite
      Barium Nitrososulphate
      Barium Nitrohydroxylaminate
      Barium Nitrite
      Barium Nitrate
      Barium Phosphide
      Barium Dihydrohypophosphite
      Barium Hydrophosphite
      Barium Hypophosphate
      Barium Orthophosphates
      Barium Pyrophosphate
      Barium Metaphosphate
      Basic Barium Phosphates
      Barium Thiophosphites
      Barium Thiophosphates
      Barium Selenophosphates
      Barium Azophosphates
      Barium Phosphimates
      Barium Arsenide
      Barium Orthoarsenite
      Barium Pyroarsenite
      Barium Orthoarsenates
      Barium Pyroarsenate
      Barium Thioarsenites
      Barium Thioarsenates
      Barium Sodium Selenoxyarsenate
      Barium Metantimonate
      Barium Thioantimonites
      Barium Chloroantimonite
      Barium Orthothioantimonate
      Barium Hypovanadate
      Barium Vanadates
      Barium Metapervanadate
      Barium Niobate
      Barium Tantalate
      Barium Pertantalate
      Barium Carbide
      Barium Carbonyl
      Barium Formate
      Barium Acetate
      Barium Oxalate
      Barium Carbonate
      Barium Thiocarbonate
      Barium Percarbonate
      Barium Cyanide
      Barium Cyanamide
      Barium Cyanate
      Barium Cyanurate
      Barium Thiocyanate
      Barium Selenocyanate
      Barium Silicide
      Barium Silicates
      Barium Fluosilicate
      Barium Stannate
      Barium Orthoplumbate
      Barium Titanate
      Barium Peroxide Pertitanate
      Barium Pertitanate
      Barium Fluoroxytitanate
      Barium Zirconate
      Barium Boride
      Barium Borates
      Barium Fluorborate
      Barium Perborate
      Barium Aluminates
      Barium Ferrite
      Barium Ferrate
      Barium Gobaltite
      Barium Dinickelite
      Barium Platinate
    Detection of Barrium
    PDB 1djh-3iqp
    PDB 3iqr-4e7y

Barium Hydroxide, Ba(OH)2






Barium oxide, like the other alkaline earth oxides, combines with water with considerable evolution of heat, forming powdered Barium Hydroxide, Ba(OH)2. It may be obtained commercially from the sulphide by the action of metallic oxides, for example zinc, copper, and lead, in the presence of water, by treatment with superheated steam, or by oxidation of the warm solution by air in the presence of Weldon mud. It may also be prepared from the carbonate by the action of superheated steam at red heat. The electrolysis of barium chloride solution with a mercury cathode, by methods similar to those employed for the production of alkali hydroxides, gives barium hydroxide. An electrolytic process has also been suggested for the preparation of barium hydroxide from barium sulphide. Barium hydroxide is formed at the anode through the interaction of hydroxyl ions with barium sulphide. A method of preparation for commercial use by the hydrolysis of tribarium silicate, or, more probably, an intimate mixture of one molecule of metasilicate with three molecules of barium carbonate, previously obtained by the fusion of barium carbonate with silica, has been described.

The heat of formation of barium hydroxide from the oxide and water is 24.24 Cal. It is an amorphous white powder of density 4.495, and it melts at 325° C. A high temperature is required to dehydrate the hydroxide. The following values have been found for the vapour pressure at different temperatures: -

Temperature, °C.630670710749789829870910951998
Pressure, mm. Hg9.217.431.55592149234355526760


Under the influence of the cathode rays, barium hydroxide fluoresces a bright orange-yellow.

The heat of solution of barium hydroxide is 11.40 Cal. It is more soluble than either strontium or calcium hydroxide, and its solubility increases considerably with temperature. The solution is strongly basic. The following values for the solubility have been found: -

Temperature, °C.0612162130415464707780
Grams hydroxide as BaO in 100 grams water1.51.82.43.03.65.07.614.023.831.970.090.77


The densities of barium hydroxide solutions, and the electrical conductivities of dilute solutions, and of concentrated, have been determined.

The solubility is considerably diminished by alkali hydroxides, and to a less extent by ammonia. It is also decreased by barium chloride, but increased by barium nitrate, probably through the formation of a complex ion. Acetone and alcohol decrease the solubility.

On electrolysing a barium hydroxide solution, less oxygen is evolved than is equivalent to the hydrogen formed, probably owing to the production of barium peroxide or hydrogen peroxide.

Carbon disulphide reacts with barium hydroxide solution at 100° C., forming barium carbonate and hydrosulphide.



Hydrates of Barium Hydroxide

Several hydrates of barium hydroxide have been described, but the existence of these has not in all cases been confirmed. At low temperatures Artus obtained the hydrate Ba(OH)2.16H2O. From solutions at ordinary temperatures the octahydrate crystallises out. The formulae, Ba(OH)2.7H2O and Ba(OH)2.9H2O, have also been assigned to the compound thus obtained.

The octahydrate may form monoclinic or tetragonal crystals, the latter being isomorphous with the corresponding strontium compound. The density is 1.656, and the heat of solution -14.5 Cal. At 78° C. it melts in its water of crystallisation, and if the temperature be raised it boils at 103° C. As the water evaporates, the boiling-point rises to 109° C., at which temperature it remains constant, whilst large brilliant rhombic crystals of the trihydrate separate out. From vapour pressure measurements, Lescoeur concluded that a compound, 3Ba(OH)2.10H2O, probably existed. This is no doubt the trihydrate. The lustre rapidly disappears on exposure to air, and in dry air the crystals effloresce, forming the monohydrate. By heating the solution in equilibrium with the trihydrate to a still higher temperature, a white crystalline powder of the monohydrate is formed. The latter is also obtained from the octahydrate by drying in vacuo or by heating for some time in a current of hydrogen at 45° C., or at 80° C. The heat of solution is 7.06 Cal. The monohydrate is changed to the hydroxide by heating in a current of hydrogen above 90°-95° C.

The monohydrate will combine with carbon dioxide at fairly low temperatures, but a slight excess of water is apparently necessary.

From vapour pressure measurements Muller-Erzbach concluded that a dihydrate can exist at 15° C.

Barium oxide forms compounds with methyl and ethyl alcohol, and also with other alcohols, such as glycerol and mannitol. According to de Forcrand these are not true alcoholates, but addition compounds, for example, 3BaO.4CH3OH and 3BaO.4C2H5OH. In aqueous methyl alcohol a hydrated compound is formed.

If ethyl alcohol and a little water be added to a methyl alcoholic solution of barium oxide, and the solution be slowly evaporated in vacuo, a compound, Ba(OCH3)2, separates out in transparent needles. It is soluble in water, slightly soluble in ethyl alcohol, and insoluble in ether or acetone.

Uses of Barium Hydroxide

Barium hydroxide was formerly used in the beet and cane sugar industries for separating otherwise uncrystallisable sugars by precipitating the sucrate and then decomposing it by carbon dioxide, but this process has now been abandoned.

It is also used as a depilatory in tanning, in the white pigment and dry colour trades for the manufacture of permanent white for example, and for the softening of water for industrial purposes.
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