Antioxidants cerium

Certain cerium and iron compounds, when properly incorporated by preoxidation, are excellent antioxidants for dimethyl silicone fluids (DMS) and methylphenylsilicone fluids (MPS). The useful life of these stabilized fluids depends on the temperature, on the concentration and dispersion of the redox metal moieties, and on the conditions of aeration—better aeration providing the longer useful life with inhibited DMS. A mechanism of stabilization by the redox metals has been proposed to account for the observed data. 

From such criteria our present experience has indicated the choice of cerium or iron antioxidants as the most feasible candidates to use in DMS and MPS fluids (6,7,9). Future study, of course, may indicate the... 

In general, DMS fluids which are properly stabilized with iron or cerium antioxidant have a useful fluid life in air of thousands of hours at or below 500°F. (260°C.) and hundreds of hours at 550°F. (288°C.) as measured by testing 40-gram samples in 150-ml. beakers in a rotating... 

Certain cerium and iron compounds can be useful as antioxidants when properly incorporated into DMS and MPS fluids by preoxidation. The conditions of fluid use determine the level of redox metal required (usually about 0.2 to 3.0 X 10"3 gram atoms/kg.) and the silicone to be used. The role of the redox metal inhibitor is to control the rate of... 

Q6.3 Vitamin C (ascorbic acid) is used in pharmaceutical formulation as an antioxidant and also has a medical use as a vitamin. Tablets of vitamin C may be assayed by titration with complex salts of cerium. The reactions occurring are as follows and are shown in Figure 6.7. 

Nalewajko-Sieliwoniuk, E., J. Nazaruk, J. Kotowska, and A. Kojlo. 2012. Determination of the flavonoids/antioxidant levels in Cirsium oleraceum and Cirsium rivulare extracts with cerium(IV)-rhodamine 6G chemiluminescence detection. Talanta 96 216-222. 

Some thiolate metal complexes, unlike the oxygen complexes referred to above are powerful antioxidants (see Chapter 1) and undergo inversion to prooxidant metal ions in sunlight. The iron, manganese, cobalt, vanadium and cerium dithiocarbamates (II) are typical examples of such restrained prooxidants. 

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