Barium oxidative addition

Rajczyk, K., Kurdowski, W., and Werynsky, B. (1992) Belite cement with barium oxide addition (in Polish). Cement-Wapno-Gips 45,9-13. 

Compared to the hydroxides of calcium and strontiuim, barium hydroxide is the most water-soluble and also the strongest base. Additionally, barium hydroxide is more difficult to convert to the oxide by heating than are the corresponding hydroxides of calcium and strontium. Barium oxide is more readily converted to the peroxide than are the oxides of the other alkaline earths. 

The viscosity of liquid silicates such as drose containing barium oxide and silica show a rapid fall between pure silica and 20 mole per cent of metal oxide of nearly an order of magnitude at 2000 K, followed by a slower decrease as more metal oxide is added. The viscosity then decreases by a factor of two between 20 and 40 mole per cent. The activation energy for viscous flow decreases from 560 kJ in pure silica to 160-180kJmol as the network is broken up by metal oxide addition. The introduction of CaFa into a silicate melt reduces the viscosity markedly, typically by about a factor of drree. There is a rapid increase in the thermal expansivity coefficient as the network is dispersed, from practically zero in solid silica to around 40 cm moP in a typical soda-lime glass. 

The recovered dg-dimethyl sulfoxide may be recycled to prepare additional deuteriomethyl iodide or purified for use as a reagent by gentle warming with a little solid sodium thiosulfate followed by distillation from barium oxide. Both products show 99% deuteration. ... 

Barium sulphate exhibits a marked tendency to carry down other salts (see co-precipitation, Section 11.5). Whether the results will be low or high will depend upon the nature of the co-precipitated salt. Thus barium chloride and barium nitrate are readily co-precipitated. These salts will be an addition to the true weight of the barium sulphate, hence the results will be high, since the chloride is unchanged upon ignition and the nitrate will yield barium oxide. The error due to the chloride will be considerably reduced by the very slow addition of hot dilute barium chloride solution to the hot sulphate solution, which is constantly stirred that due to the nitrate cannot be avoided, and hence nitrate ion must always be removed by evaporation with a large excess of hydrochloric acid before precipitation. Chlorate has a similar effect to nitrate, and is similarly removed. 

Barium Oxide (Barium Monoxide, Baryta, Barium Protoxide, Calcined Baryta). BaO, mw 153.36 colorl or white to yelsh-white deliq powd mp 1923°, bp 2000°, d 5.72g/cc. Sol in dil acids, ethanol, methanol and w (decomps with a large amt of heat being evolved). Prepn is by thermal decompn of BaCOj under high vacuum. It is a product of the burning of the many barium compds present in pyrots and, as discussed above, it is used as an anti-barrel wear additive in proplnt compns... 

The powder is principally composed of zinc oxide (Table 6.2). Magnesium oxide is found in all current commercial brands in amounts that range from 3 to 10%. Alumina and silica are sometimes to be found. Present day compositions show less variation than formerly when bismuth, calcium and barium oxides, or sometimes no additives, were to be found in commercial examples (Paffenbarger, Sweeney Isaacs, 1933). 

Barium oxide and sodium hydride are more potent catalysts than silver oxide. With barium oxide catalysis, reactions occur more rapidly but O-acetyl migration is promoted. With sodiun hydride, even sterically hindered groups may be quantitatively alkylated but unwanted C-alkylation Instead of, or in addition to, 0-alkylatlon is a possibility. Sodium hydroxide is a suitable catalyst for the alkylation of carboxylic acids and alcohols [497J. 

In dim red light, the weighed hydrazide contained in one of the 500 ml flasks (ca. 67 g 95% of theory) is washed into a 1000 ml beaker with 263 ml IN hydrochloric acid. 239 ml distilled water, 239 ml ethanol (95%), and 37 ml 2,4-pentanedione are added, and the well-mixed solution left to stand in the dark at room temperature until the reaction is complete, i.e., about 30 minutes. The reaction mixture is neutralized with the addition of 263 ml 1 N sodium hydroxide, and the beaker covered with parafilm and refrigerated to ensure complete precipitation. The pyrazole is filtered at the pump, the mother liquor being returned to the beaker and used to wash out the last few crystals, washed with cold water, and sucked dry under a stream of dry nitrogen. The product is dried in vacuo over barium oxide or phosphorus pentoxide for at least twelve hours before proceeding to the next step, wherein anhydrous conditions will increase yield. Hofmann calls for drying the pyrazole in vacuo at 60°, which indicated the product to be fairly stable. So all the hydrazide is converted prior to aminization. 

Lanthanum glasses are usually low silica and consist substantially of boric acid, zirconia, barium oxide and lanthanum with various other additives to help stabilize the viscosity and liquidus or crystallization temperature. Z, 10)... 

Pure pyridine dried over barium oxide was used. A considerable amount of heat is liberated on addition of the pyridine to the mixture. 

Vanadium Nitrates.—No nitrates of vanadium have been isolated. When hypovanadic oxide is dissolved in nitric acid the blue solution which results probably contains vanadyl nitrate, V0(N03)2, but on evaporation oxidation ensues and hydrated vanadium pentoxide is obtained. Blue solutions of vanadyl nitrate arc more conveniently obtained by precipitating vanadyl chloride with silver nitrate or vanadyl sulphate with barium nitrate. Addition of nitric acid to hexammino-vanadium trichloride yields hexammino-vanadium nitrate,10 [V (NH3)6](N03)3. 

Zhang, G., Hattori, H. and Tanabe, K. Aldol addition of acetone, catalyzed by solid base catalysts magnesium oxide, calcium oxide, strontium oxide, barium oxide, lanthanum-(III) oxide and zirconium oxide, Appl. Catal., 1988, 36, 189-97. 

The ordinary oxide of barium has the formula BaO, and it forms the corresponding base Ba(OH)2 when it combines with water. Barium salts are formed when this base is neutralized with acids. In addition there is another oxide of barium containing twice as much oxygen, Ba02, which is easily obtained when barium oxide is heated to a dull red heat in air free from carbon dioxide. 

In order to obtain light and porous barium oxide barium carbonate is mixed with petroleum coke having a low ash content or with finely ground pitch or with lamp black this mixture is calcinated at a temperature of 1200—1300 °C in a battery of retorts heated by generator gas and placed in a brick chamber. The retorts are made of special ceramic material with addition of carborundum. 

Drying of nonaqueous solutions can be carried out by various methods which include the addition of sodium, in the form of wires, or powdered solids such as barium oxide alternatively, a high potential difference between auxciliary electrodes can be used to getter the and OH" ions. The quality of the nonaqueous work in electrochemistry is increasing rapidly. 

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