Determination of Hydroquinol

Iodine oxidizes hydroquinol into p-quinone in hydrogen carbonate medium. Actually, the reaction is equilibrated  

The reaction is quite similar to that of iodine with arsenious acid. The hydrogen carbonate buffer is used to displace the reaction toward the right. The standard potential of the couple p-quinone/hydroquinol is E° = 0.70 V. Resorcinol (meta-diphenol) and pyrocatechol (ortho-diphenol) do not give any reaction of analytical interest with iodine. 

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