Fig. 1From: Iron-gall inks: a review of their degradation mechanisms and conservation treatmentsChemical structures of gallic acid, gallate, monogalloyl glucose and pentagalloyl glucose. In the first two, the main functional group is based on a carboxylic acid and the other on an ester. Phenolic OH groups are also important in the formation of the iron(II)-phenol complex. The galloyl esters of glucose can also be named gallotanninsBack to article page