New insights into iron-gall inks through the use of historically accurate reconstructions

Heritage Science

Table 2 Preparation of the references for the iron-polyphenol complexes

	Water/mL	Polyphenol	FeSO₄	Gum arabic^a	Polyphenol:FeSO ^b₄	Final pH
Gallic acid	40	2.35 mmol 0.442 g	2.35 mmol 0.65 g	− 0.221 g	1:1	1.66
Ellagic acid	40	2.35 mmol 0.710 g	4.67 mmol 1.3 g	− 0.355 g	1:2	2.21
Digalloyl glucose	1.75	0.103 mmol 0.005 g	0.103 mmol 0.028 g	− 0.002 g	1:1	2.86
Pentagalloyl glucose	2.24	0.132 mmol 0.0125 g	0.264 mmol 0.073 g	− 0.006 g	1:2	2.09
Tannic acid	20	1.16 mmol 1.99 g	2.35 mmol 0.65 g	− 0.65 g	1:2	1.49

^aThe ratio of gum arabic was based on the medieval treatises, where the galls:gum arabic ratio is mainly 1:0.5
^bThe ratio is in molarity and was normalized for the polyphenol concentration