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Term for a chemical reaction in which an atom or molecule accepts electrons (reduces) and another substance gives up these electrons (oxidises). In a narrower sense, in connection with oxygen, a reducing agent is the term used to describe the substance that removes oxygen from another, such as oxide (oxygen compound), and is itself oxidised in the process. Many substances can be both oxidised and reduced. Whether a substance is a reducing or an oxidising agent depends solely on the reaction partner. A very important reducing agent for winemaking is sulphur. As a reducing agent it can react with oxygen to form sulphur dioxide, but also as an oxidising agent it can convert metals (e.g. contacts of wine with metallic substances in the cellar) into their sulphides and thus cause a wine defect, which manifests itself as a metallic tone.

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Roman Horvath MW

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Roman Horvath MW
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