Barium redox reactions

The barium bis(dnunod) complex is readily prepared by a redox reaction combining elemental barium with Hdnunod (equation 43). Purified by distillation of the excess Hdnunod, Ba(dmmod)2 was identified to be authentic by elemental analysis, and found to be monomeric in benzene solution. Examination of the literature reports currently available indicates that this represents the first observation of an ambient condition liquid barium compound that is based on )3-diketonate ligands. Utihzing the data, it would appear that the metal center is six coordinate. Examination of space-filling molecular models lends some credence to this suggestion. 

The above results suggest that small barium aggregates are better reducing agents than atomic barium. This may be understood with the help of Figure 20, by considering that barium aggregates more easily transfer an electron in a redox reaction than barium atoms. Chevaleyre and co-workers measured the ionization potentials... 

Procedure. A drop of the test solution in a micro test tube is acidified with 1-2 drops of barium chloride solution containing enough saturated potassium permanganate solution to color the solution distinctly. After waiting for 5-10 minutes, the excess permanganate and the manganese dioxide formed in the redox reaction are destroyed by adding several drops of saturated hydroxyl-amine chloride solution. A positive response is indicated if a violet precipitate remains. 

Surface grafting of barium sulfate is interesting Ifom the point of view of the kinetics of such reactions. Barium sulfate like calcium carbonate, is an inert filler. So it is necessary to modify its surface. First, barium chloride is reacted with sodium sulfate in the presence of a small amount of sodium 12-hydroxystearate. This introduces a controlled number of hydroxyl stearate sites onto the barium sulfate surface. The reaction is followed by a redox graft polymerization of acrylamide initiated by the hydroxyl stearate groups and ceric ion as a catalyst. Figures 6.9 to 6.11 show the effect of reaction substrates concentrations on polymerization rate. 

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