Synthetic Tannins | Page 2

equally
good and more varied synthetic tannins than has hitherto been deemed
possible. The originator of these products and his acolytes must at least

share the credit with those who, in spite of the limitations necessarily
set by the former, have been able to find new and better ways.
In his book Dr. Grasser gives a short review of the necessary forerunner
of any work upon synthetic tannins: the investigations and syntheses of
the natural tannins. It is certainly to be hoped that we may soon see
such works as those of Fischer's and Freudenberg's, recently published,
translated into English. For the guidance of the reader it may be noted
that a short account of the works of these authors may be found in the
_Journal of the Society of Leather Trades' Chemists_, vol. v. (May
issue); in addition to this some of the matter contained in the chapter on
synthesis of tanning matters appeared in the January 1921 issue of the
_Journal of the American Leather Chemists' Association._
In addition to these two sections, the last part of this book deals with
the practical applications of synthetic tannins, and it is hoped that the
tanner will find much valuable information in these pages. The main
outlines of the synthesis of tanning matters should prove of great value
to the chemist engaged in this branch of chemical technology.
The translator takes great pleasure in the acknowledging the valuable
assistance rendered him by Mr. Robin Bruce Croad, A.R.T.C., F.I.C.,
and by Mr. Arthur Harvey.
F. G. A. ENNA

CONTENTS
Introduction: Classification of Synthetic Tannins

PART I SECTION I
The Synthesis of Vegetable Tannins
1. Tannin 2. Digallic Acid 3. Ellagic Acid 4. Depsides
Carbomethoxylation of Hydroxybenzoic Acids Chlorides of
Carbomethoxyhydroxybenzoic Acids Preparation of Didepsides
Preparation of Tridepsides Preparation of Tetradepsides Tannoid
Substances of the Tannin Type Chart showing the Decomposition of
Products of Tannin

SECTION II
Synthesis of Tanning Matters
1. Aromatic Sulphonic Acids 2. Condensation of Phenols Condensation
of Hydroxybenzene Condensation of Dihydroxybenzene Trihydroxy
benzene Polyhydroxybenzenes Quinone Phenolic Ethers Nitro Bodies
Amino Bodies Aromatic Alcohols Aromatic Acids 3. Condensation of
Naphthalene Derivatives 4. Condensation of the Anthracene Group 5.
Di- and Triphenylmethane Groups 6. Summary
Table
SECTION III
Tanning Effects of Mixtures and Natural Products
1. Mixture of Phenolsulphonic Acid and Formaldehyde 2. Mixture of
Phenolsulphonic Acid and Natural Tannins 3. Tanning Effects of
Different Natural Substances
SECTION IV
Methods of Examining Tanning Matters

PART II
Synthetic Tannins: Their Industrial Production and Application
A. Condensation of Free Phenolsulphonic Acid B. Condensation of
Partly Neutralised Phenolsulphonic Acid C. Condensation of
Completely Neutralised Phenolsulphonic Acid D. Condensation of
Cresolsulphonic Acid E. Relative Behaviour of an Alkaline Solution of
Bakelite and Natural Tannins F. Dicresylmethanedisulphonic Acid
(Neradol D) 1. Neradol D Reactions 2. Electro-Chemical Behaviour of
Neradol D 3. The Influence of Salts and Acid Contents on the Tanning

Effect of Neradol D 4. Phlobaphene Solubilising Action of Neradols 5.
Effect of Neradol D on Pelt 6. Reactions of Neradol D with Iron and
Alkalies 7. Reagents suitable for Demonstrating the Various Stages of
Neradol D Tannage 8. Combination Tannages with Neradol D (1)
Chrome Neradol D Liquors (2) Aluminum Salts and Neradol (3) Fat
Neradol D Tannage 9. Analysis of Leather containing Neradol D 10.
Properties of Leather Tanned with Neradol D 11. Neradol D, Free from
Sulphuric Acid 12. Neutral Neradol G. Different Methods of
Condensation as Applied to Phenolsulphonic Acid 1. Condensation
Induced by Heat 2. Condensation with Sulphur Chloride 3.
Condensation with Phosphorus Compounds 4. Condensation with
Aldehydes 5. Condensation with Glycerol
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
(coloration with iron salts), but they cannot be regarded as tannins from
either a technical or a physiological standpoint.
As regards their chemical constitution,