The Vegetable Tannins₁

Abstract

THE subject of the vegetable tannins₂ is a small field in organic chemistry. Although the subject has been considerably developed and extended in recent years, its beginnings date back to the rise of modern chemistry. One hundred and fifty years ago, Carl Wilhelm Scheele, one of the discoverers of oxygen, in his dark apothecary's shop at Køping in Sweden, allowed an aqueous infusion of Turkish oak galls to be fermented by moulds, doubtless not the first occasion that such a fermentation took place in a pharmaceutical laboratory. But Scheele was one of the best observers chemistry ever had. He noticed that a crystalline substance settled down below the layer of the mould and he was able to recrystallise this substance from water. He called it sal essentiale gallarum, and it became known in the literature as gallic acid, having the formula