Desiccants barium oxide

Sodium and potassium hydroxides. The use of these efficient reagents is generally confined to the drying of amines (soda lime, barium oxide and quicklime may also be employed) potassium hydroxide is somewhat superior to the sodium compound. Much of the water may be first removed by shaking with a concentrated solution of the alkali hydroxide. They react with many organic compounds (e.g., acids, phenols, esters and amides) in the presence of water, and are also soluble in certain organic liquids so that their use as desiccants is very limited... 

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. 

Crystal structure of 60 revealed that the complex existed as a dimeric species where the two chromium centers are bridged through the indane oxygen and each chromium metal bears one molecule of water (Figure 17.6). It was therefore proposed, as for the inverse electron-demand hetero Diels-Alder reaction, that the barium oxide desiccant removed one molecule of bound water from the catalyst dimer, which opened one coordination site for binding of the substrate carbonyl.26... 

Preparation of Barium Hexafluorosilicate, BaSiF 6. Twenty-five grams of barium chloride 2-hydrate (0.10 mol) is dissolved in 70 ml. of water. Aqueous fluorosilicic acid (30%) is added until precipitation is complete this requires about 40 ml. of the solution. The freshly precipitated barium hexafluorosilicate is filtered and washed until free from chloride. The product is dried in an oven at 110 to 120° and then dried further in a desiccator over phosphorus ) oxide or porous barium oxide. The yield is nearly quantitative. 

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 organic adsorbate in a small vessel was put into a phosphorous oxide desiccator and its vapor was allowed to adsorb on the clay at room temperature. When the adsorbate was solid, a clay sample was Immersed into the cyclohexane solution and dried in the desiccator. In the adsorption of pyridine, barium oxide was used as a drying agent. The formation rate of colored complexes was dependent on the adsorbate molecules and the dryness of montmorillonite. In the case of anisole or phenol, the color began to appear at once when the adsorbate was brought into contact with the dried montmorillonite, but it took about two weeks to finish the reaction in pyridine adsorption. 

These can be prepared by electrolytic oxidation of chlorates(V) or by neutralisation of the acid with metals. Many chlorates(VII) are very soluble in water and indeed barium and magnesium chlorates-(VII) form hydrates of such low vapour pressure that they can be used as desiccants. The chlorate(VII) ion shows the least tendency of any negative ion to behave as a ligand, i.e. to form complexes with cations, and hence solutions of chlorates (VII) are used when it is desired to avoid complex formation in solution. 

Barium manganate [7787-35-] J M 256.3. Wash with conductivity H2O by decantation until the supernatant gives a faint test for Ba . Remove excess H2O in vac (IMPORTANT), then heat at 100° and the last traces of H2O are removed in a vac desiccator over P2O5. Store over KOH. It disproportionates in hot H2O or dil acid to Ba(MnO2)2 and Mn02, and is a mild oxidant. [7ACS 44 1965 1924-, Inorg Synth 11 56 I 960]. 

Five and twenty-three hundredths grams of germanium(IV) oxide (0.05 mol) is dissolved in 15 ml. of a concentrated aqueous solution of hydrofluoric acid (47 %). A platinum evaporating dish or a polyethylene plastic beaker is used to keep silicon contamination to a minimum. A solution of 10.5 g. of barium chloride (0.05 mol) in 50 ml. of water is added. Barium hexafluorogermanate forms as a white, granular precipitate, which is filtered and washed free of chloride. The product is dried by heating to 300° in vacuo and is stored in a desiccator over phosphorus(V) oxide. The yield is 15.24 g. (94%). 

SAFETY PROFILE A poison. An unstable material. An oxidizer. When refluxed with an alcohol highly explosive alkyl perchlorates are formed. When heated to decomposition it emits toxic fumes of Cl . A desiccant. See also PERCHLORATES and BARIUM COMPOUNDS. 

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