Sulfur dioxide oxidation temperature changes

Since chromium(III) oxide is virtually inert, chromium oxide green pigments are remarkably stable. They are insoluble in water, acid, and alkali and are thus extremely stable to sulfur dioxide and in concrete. They are light, weather, and temperature resistant. A change of the tint only occurs above 1000 °C due to particle growth. 

The chemical stability of PE is comparable to paraffin. It is not affected by mineral acids and alkalis. Nitric acid oxidizes PE and halogens react with it by substitution mechanisms. By chlorination in the presence of sulfur dioxide, chlorine groups and sulfonyl chloride are incorporated and an elastomer is formed. Oxidation of polyethylene which leads to structural changes can occur to a measurable extent at temperatures as low as 50 °C. Under the influence of ultraviolet light the reaction can occur at room temperature. 

Ethanal is the most important of these compounds (Table 2.6). The many ways it can be produced and its high reactivity (the CHO radical has extensive chemical affinities), as well as its rapid combination with sulfur dioxide at low temperatures and its organoleptic properties, make ethanal a very important component of wine. The presence of ethanal, produced by the oxidation of ethanol, is closely linked to oxidation-reduction phenomena. It is involved in the alcoholic fermentation mechanism. Furthermore, ethanal plays a role in the color changes occurring in red wines during aging by facilitating the copolymerization of phenols (anthocyanins and catechins) (Section 6.3.10). 

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