REGISTER OF AUTHORS

INDEX




INTRODUCTION

CLASSIFICATION OF SYNTHETIC TANNINS

In laying down a definition of "Synthetic Tannins," it is first of all
necessary to clearly define the conception of "tannin." Primarily,
tannins may be considered those substances of vegetable origin which may
be found, as water-soluble bodies, in many plants, exhibiting certain
chemical behaviour, possessing astringent properties and being capable
of converting animal hide into leather. This latter property of the
tannins, that of converting the easily decomposable protein of animal
hide into a permanently conserved substance and imparting to this
well-defined and technically valuable properties, has become the
criterion of the practical consideration of a tannin. It appears that
different substances certainly show the chemical reactions peculiar to
the tannins, and to a certain extent also exhibit astringent character
without, however, possessing the important property peculiar to the
tannins of converting hide into leather. Such substances, in our
present-day terminology, are termed pseudo-tannins (_e.g._, the "tannin"
contained in coffee-beans). Decomposition products of the natural
tannins, to which belong, for instance, gallic acid and the
dihydroxybenzenes, exhibit the well-known reactions of the tannins