Barium hydroxide.octahydrate Ba

FIGURE 6.9 The endothermic reaction between ammonium thiocyanate, NH4SCN, and barium hydroxide octahydrate, Ba(0H)2-8H20, absorbs a lot of heat and can cause water vapor in the air to freeze on the outside of the beaker. 

Barium hydroxide octahydrate, Ba(OH)2 8 H20, is a crystalline compound that contains eight water molecules clustered around the barium atom. We ll learn more about hydrates in Section 14.15. 

Baryta water (saturated). Shake 5 g barium hydroxide octahydrate, Ba(0H)2.8H20, with 100 ml water. Allow to stand for 24 hours. Use the clear supernatant liquid for the tests. 

Or consider the reaction described in the chapter opening, in which crystals of barium hydroxide octahydrate, Ba(OH)2 8H2O, react with crystals of ammonium nitrate, NH4NO3. 

According to the Lewis theory, alkaline earth metal hydroxides are weaker bases than their oxides, the order of the strength of the basic sites being Ba(OH)2> SrO(OH)2 > Ca(OH)2 > Mg(OH)2. The hydroxides have been used recently as solid catalysts for organic transformations, such as the conjugate addition of methanol to a, S-unsaturated carbonyl compounds (12), cyanoethylation of alcohols (163,164), and transesterification reactions (166,167,171,172) which are described above. The extensive work of Sinisterra et al. (282) on the number and nature of sites and on the catalytic activity of the most basic alkali metal hydroxide, Ba(OH)2, is emphasized. It was found that commercial barium hydroxide octahydrate can be converted into... 

What do a melting ice cube and the reaction of barium hydroxide octahydrate have in common The common feature of these and all other spontaneous processes that absorb heat is an increase in the amount of molecular disorder, or randomness, of the system. The eight water molecules rigidly held in the Ba(OH)2 8 H20 crystal break loose and become free to move about in the aqueous liquid product similarly, the rigidly held H20 molecules in the ice lose their crystalline ordering and move around more freely in liquid water. 

In this equation, the 8H2O in Ba(OH)2 8H2O indicates the presence of eight water molecules. This compound is called barium hydroxide octahydrate. 

Barium hydroxide octahydrate [12230-71-6] M315.5, m 78", pKj 13.13, pK 13.36. It crystalUses from water (Iml/g) and readily absorbs CO2 from air. It effloresces to the monohydrate. It dehydrates to Ba(OH)2 in dry air at 100". An aqueons solution (baryta water) absorbs CO2 to form a white precipitate of BaCOs. 

Barium hexaferrite. See Barium ferrite Barium hexafluorosilicate Barium hexafluorosilicate (2-). See Barium fluosilicate Barium hydroxide. See Barium hydroxide lime Barium hydroxide lime CAS 17194-00-2 (anhyd.) 12230-71-6 (octahydrate) EINECS/ELINCS 241-234-5 Synonyms Barium dihydroxide Barium hydroxide Caustic baryta Definition Mixt. of barium hydroxide octahydrate and calcium hydroxide Empirical BaH202 Formula Ba(OH)2... 

Barium hydroxide is the strongest base and has the greatest water-solubility of the alkaline-earth elements. Barium hydroxide (barium hydrate, caustic baryta) exists as the octahydrate [12230-71 -6], Ba(OH)2 8H20, the monohydrate [22326-55-2], Ba(OH)2 H20, or as the anhydrous [17194-00-2] material, Ba(OH)2. The octahydrate and monohydrate have sp gr 2.18 and 3.74, respectively. The mp of the octahydrate and anhydrous are 77.9 °C and 407°C, respectively. 

Barium hydroxide is made by dissolving barium oxide in hot water. The octahydrate, Ba(0H)2 8H20, crystaUizes upon cooling. It also is prepared by precipitation with caustic soda from an aqueous solution of barium sulfide ... 

Barium Hydroxide. Exists as Anhydrous, Ba(OH)2, available commercially Monohydrate, Ba(0H)2.H20, wh powd, highly toxic, has m any industrial uses Pentahydrate, Ba(OH)2.5H2o[ translucent free-flowing wh flakes, d 651bs/cu ft, highly toxic and Octahydrate, wh crysts, mpj 78°, loses w of crystallization at 408°, d 2.18 g/cc sol in water, ale eth, highly toxic prepd by dissolving Ba oxide in w with subsequent crystallization and by other methods, used in org prepns, Ba salts in analytical chem Refs 1) CondChemDict (1971), p 92-R to 93-L 2) US Spec M1L-B-36212 (May 1964)... 

Barium Hydroxide. Exists as Anhydrous, Ba(OH)2, available commercially Monohydrate, Ba(0H)2.H20, wh powd, highly toxic, has mlany industrial uses Pentahydrate, Ba(OH)2.5H2o[ translucent free-flowing wh flakes, d 651bs/cu ft, highly toxic and Octahydrate, wh crysts, mp ... 

Barium hydroxide [33, 34] is a strong base which has been employed not only in organic synthesis but also for other purposes. The commercially available octahydrate, l a(OI 1)2 8 11,/) is often used after transformation to the anhydrous form at 200-500 °C. Dehydrated Ba(OH)2 activated at 200°C is denoted C-200. It is known to be a heterogeneous basic catalyst in the Horner-Wadsworth-Emmons (HWE) reaction of triethyl phosphonoacetate (69) with aldehydes 70 to give the 3-substituted ethyl acrylates 71 (Scheme 5.13) [35]. The HWE reaction proceeds at 70 °C in 1,4-dioxane with a small amount of water. The yields of products 71 are usually better than those provided by typical basic catalysts such as NaOH or... 

Purification of barium salts n. Impurities which can be separated as sulfides are removed by following the directions given for SrO (II). The hydroxide octahydrate is not altogether suitable for further purification (removal of residual traces of Sr, Ca, Mg, etc.) since its recrystallization, while removing all traces of Ca, does not lead to complete removal of Sr. The nitrate, on the other hand (according to Richards), is very well suited for removal of the last traces of Sr, Ca, Mg, K and Na from Ba salts. 

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