An excerpt from the beginning of SECTION I. THE DISCOVERY OF THE TANNINS.
The history of tannin as a proximate principle takes its beginning in France during the period between 1790 and 1800. Previous to that time the histories of leather, galls, and oak-bark are our only sources of information regarding the development which led to the discovery of tannin.
Great discoveries are rarely made without some warning; in reviewing their origin we see that they have had a gradual birth, and the exact date which indicates the beginning of their existence cannot be determined. In these evolutions of a discovery there are sometimes periods of comparative inactivity, succeeded by sudden and great advances. The history of tannin has not been an exception to the rule of gradual discovery, for we find among the earlier writers on the subject a disposition to attribute the astringency of galls and oak-bark to some peculiar principle, which, however, they did not separate or name.
Dr. William Lewis, in his "Philosophical Commerce of the Arts, London, 1763," calls attention to the presence of a substance in certain vegetable infusions, which, when mixed with "green vitriol," produces "a deep black liquor, of most extensive use for dyeing and staining black. The power by which they produce this blackness and their astringency, or that by which they contract an animal fibre, seem to depend upon one and the same principle, and to be proportional to one another." "Of the properties of this colouring and astringent matter, little more is known than that it is dissolved and extracted from the subject both by water and spirit of wine, and that it does not exhale in the evaporation of the liquors by heat."
English writers on tannin usually ascribe to Dr. Lewis the honor of having a part in its discovery, but further than for writing the above quotation of facts, which were well known before his time, it is unreasonable to give him credit.
He was followed by other investigators, chiefly on galls and oak-bark, especially in the relation of the latter to tanning, which gradually led to the discovery of gallic acid by Scheele in 1786.