Barium oxide pressure

Industrial grade dimethylformamide is purified by distillation, first at atmospheric pressure to remove most of the water in the initial small fraction, and then by distillation at reduced pressure from barium oxide, b.p. 63° (30 mm.). 

Diaminopropane (97%, Aldrich Chemical Company, Inc.) was distilled at atmospheric pressure under nitrogen from barium oxide and stored... 

Banum oxide. [CAS 1304-28-5]. BaO. white solid, mp about 1900°C. reactive with H20 to forni barium hydroxide. Barium peroxide, Ba02-8H20, white precipitate, formed by reaction of barium salt solution and hydrogen or sodium peroxide, yields anhydrous banum peroxide upon heating at 100°C in a current of dry air. Anhydrous barium peroxide is also fonned by heating barium oxide in air or oxygen under pressure (at somewhat over one atmosphere pressure) and temperature of 400°C. 

Commercial grades of DMF may be purified initially by azeotropic distillation with benzene (CAUTION). Distil a mixture of 1 litre of DMF and 100 ml of benzene at atmospheric pressure and collect the water benzene azeotrope which distils between 70 and 75 °C. Shake the residual solvent with powdered barium oxide or with activated alumina (Grade I), filter and distil under nitrogen at reduced pressure collect the fraction having b.p. 76°C/39mmHg or 40°C/10mmHg. The distillate is best stored over a Type 4A molecular sieve. 

This versatile solvent has good chemical stability in the absence of acids and bases which catalyse the cleavage of the lactam ring. It is most conveniently dried by initial azeotropic distillation with previously dried benzene or toluene as described for DMF, and the residual liquid is shaken with barium oxide, the desiccant is removed and the solvent is fractionally distilled under reduced pressure (c. 20 mm). The pure solvent has b.p. 94-96 °C/20 mmHg, or 202 °C/760mmHg. 

HMPT is now thought to be a potent carcinogen. It should be handled with extreme care inhalation of the vapour and contact with the skin should be avoided. This solvent is miscible both with water and with many polar and non-polar organic solvents with the exception of saturated aliphatic hydrocarbons. It forms a complex with chlorinated solvents by which means it may be removed from aqueous solutions. The solvent may be dried by shaking with calcium hydride or barium oxide followed by distillation under reduced pressure and... 

At the equilibrium point of this reaction the partial pressure of carbon monoxide is many times that of the carbon dioxide thus it would be much above 1 atmosphere, and carbon monoxide would escape from the crucible. With excess powdered charcoal in the crucible, therefore, both reactions would continue to run until all the barium carbonate had changed to barium oxide. Carbon monoxide does not react with barium oxide. 

Methyl methacrylate (MMA), ethyl methacrylate (EMA), n-butyl methacrylate (n-BMA), styrene (Sty), acrylonitrile (AN), vinyl acetate (VA), methyl acrylate (MA), isoprene (IP), and isobutyl vinyl ether (IBVE) were all dried over anhydrous barium oxide and distilled at or below 25°C. (except n-BMA, 35°-40°C.) under low nitrogen pressure. Acrylic acid (AA) was dried over anhydrous sodium sulfate and distilled under vacuum before use. 

This can be dried with Linde-type sieves 4A or 13X, by prolonged contact and by passage through a column of the material, then distilled under reduced pressure. Other drying agents include calcium hydride, calcium oxide, barium oxide and calcium sulphate. It can also be fractionally crystallized by partial freezing. 

The barium oxide was obtained in a hard and porous condition by ignition of the nitrate. Pieces about the size of a walnut were heated to 000° C. in vertical steel retorts into which air, purified from carbon dioxide and from most of its moisture, was conducted under a pressure of about 10 lb. per sq. inch. After seven minutes the pressure was reduced to 4 inches (10 cm.) of mercury, the temperature remaining constanf, whereon the absorbed oxygen was evolved. This process was repeated four times per hour, and a gas of 95 per cent, purity obtained.8... 

The diaquo compound is placed in an Abderhalden dr3dng apparatus with barium oxide as the desiccant. After 14 hours at 57° (or 6 hours at 67°) and pressure of 30 mm. (a water... 

The barium carbonate can be separated by filtration and when heated loses carbon dioxide, leaving barium oxide which is available for reconversion into barium peroxide. The hydrogen peroxide will be in the filtrate which can be concentrated by evaporation under reduced pressure. 

Preparation. Nitrobenzene is dried over calcium chloride and then distilled from barium oxide, 3-hexylthiophene is distilled under reduced pressure. 

It has been observed that if there is introduced into the mixture a third mineral substance without vapour pressure, nothing is changed. There can then be added to the mixture dehydrating agents such as quicklime, barium oxides, caustic soda or caustic potash, it being possible to have the last two dehydrating agents, if necessary, in the form of an approximately saturated aqueous solution. 

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