4-[Tri(n-butyl)phosphonio]-2,5-diselenoxo-1,3-diselenacyclopentanide

✍ Scribed by Prof. Dr. Heinz P. Fritz; Dr. Gerhard Müller; cand. chem. Gabriele Reber; Dipl.-Chem. Michael Weis

• Publisher: John Wiley and Sons
• Year: 1985
• Tongue: English
• Weight: 252 KB
• Volume: 24
• Category: Article
• ISSN: 0044-8249
• DOI: 10.1002/anie.198510581

✦ Synopsis

particle sizes at pH 0, 1, and 2 ; the precipitates settle quickly and are easy to wash. Particle size, surface characteristics,['] bulk density, and electrochemical properties['"' of the product depend strongly on the p H value during the precipitation (Fig. 1, left and middle). The properties of the samples obtained at p H 2 and p H 1 are nearly identical. At the same p H values, uncontrolled precipitation affords precipitates that are difficult to filter and wash and that, after drying, are present as nonuniform agglomerates (Fig. 1, right). The preparations obtained by controlled precipitation belong structurally to the 6-Mn02 group:L81 those prepared by uncontrolled precipitation are primarily amorphous.

Particularly noteworthy is the possibility of obtaining uniform particles with very large surface areas (169 m2/g) and also with much smaller surface areas (0.4 m'/g) by controlled precipitation of manganese dioxide at p H 0 and at pH 1 and 2, respectively. The latter are somewhat similar in appearance to the manganese nodules found in the ocean.