Separators manganese dioxide, magnesium

Diacetylbenzene from 4-ethylacetophenone Magnesium nitrate hexahydrate (30 g) is dissolved in water (250 ml), and 4-ethylacetophenone (15 g) is added. The mixture is warmed to 50° and powdered potassium permanganate (16 g) is added in small portions with rapid stirring. The temperature rises to 70°. Oxidation is complete in 2h, the mixture is then allowed to cool and the manganese dioxide formed is filtered off and washed with ether. The aqueous filtrate is also shaken with ether. The combined ether extracts are dried over calcium chloride, filtered, and evaporated, whereupon /7-diacetylbenzene separates (13.8 g, 84% m.p. 114°). 

Several other hydroxides have been used both for general coprecipitation and for specific separations. Lanthanum hydroxide has been used (47, 48) as a convenient collector and subsequent release agent for atomic absorption spectroscopy. Titanium hydroxide coprecipitates copper and zinc from seawater (49), and chromium(III) hydroxide precipitates cadmium(II) (50) and zinc (57). Other authors have used magnesium hydroxide (52, 53), manganese dioxide (54, 55), and zirconium hydroxide (56, 57) to collect trace metals from natural waters. Thallium(III) was coprecipitated with zirconium hydroxide at pH 4.3-6.7 and thallium(I) at pH 7.0-13.0 (57). Beryllium (58) and antimony (59) can be quantitatively coprecipitated with a variety of hydroxides including titanium and zirconium, depending on the pH used. 

Magnesium/Manganese Dioxide Battery. This reserve battery consists of a magnesium anode and a manganese dioxide cathode. - It is activated by pouring an aqueous magnesium perchlorate electrolyte into the cells of the battery, where it is absorbed by the separators. Electrolyte absorption occurs within a few seconds at 0°C or above, but 3 min or more are required at -40°C due to the viscosity of the electrolyte. 

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