Chapter I: Front Matter

Transcriber's Note:

Minor typographical errors and inconsistencies have been corrected. Some words had inconsistent hyphenation throughout the book; these have been made consistent.

In the mathematical and chemical expressions, the caret character represents "to the power of", e.g. e^2 means e-squared. Curly braces are used to represent underscores, e.g. n{1} means n with a subscript of 1. Equal signs are used to represent =bold words=, and underscores are used to represent italics.

On page 152 NaCO{23} has been corrected to Na{2}CO{3}. On page 212, the variable n has been replaced with the correctly subscripted forms n{1} and n{2}.

The index entry for Hemlock bark had no page number in the original text, so the correct page number, 34, has been supplied.

Ions are shown as Fe+++, instead of using superscripts.

There is some inconsistency in the notation used in the original text for chemical formulae such as Na{2}Cr{2}O{7}(2H{2}O). These have been regularized to use the modern mid-dot, for example, Na{2}Cr{2}O{7}·2H{2}O.

Greek letters in the original have been represented in this version by the name of the letter enclosed in square brackets, e.g. [alpha].

ANIMAL PROTEINS

BY

HUGH GARNER BENNETT, M.Sc. (LEEDS)

MEMBER OF THE SOCIETY OF LEATHER TRADES' CHEMISTS; FORMERLY ASSISTANT
LECTURER AND DEMONSTRATOR AT THE LEATHER INDUSTRIES DEPARTMENT OF THE
UNIVERSITY OF LEEDS

AUTHOR OF "THE MANUFACTURE OF LEATHER"

LONDON

BAILLIÈRE, TINDALL AND COX 8, HENRIETTA STREET, COVENT GARDEN
1921

(_All rights reserved_)

GENERAL PREFACE

The rapid development of Applied Chemistry in recent years has brought about a revolution in all branches of technology. This growth has been accelerated during the war, and the British Empire has now an opportunity of increasing its industrial output by the application of this knowledge to the raw materials available in the different parts of the world. The subject in this series of handbooks will be treated from the chemical rather than the engineering standpoint. The industrial aspect will also be more prominent than that of the laboratory. Each volume will be complete in itself, and will give a general survey of the industry, showing how chemical principles have been applied and have affected manufacture. The influence of new inventions on the development of the industry will be shown, as also the effect of industrial requirements in stimulating invention. Historical notes will be a feature in dealing with the different branches of the subject, but they will be kept within moderate limits. Present tendencies and possible future developments will have attention, and some space will be devoted to a comparison of industrial methods and progress in the chief producing countries. There will be a general bibliography, and also a select bibliography to follow each section. Statistical information will only be introduced in so far as it serves to illustrate the line of argument.

Each book will be divided into sections instead of chapters, and the sections will deal with separate branches of the subject in the manner of a special article or monograph. An attempt will, in fact, be made to get away from the orthodox textbook manner, not only to make the treatment original, but also to appeal to the very large class of readers already possessing good textbooks, of which there are quite sufficient. The books should also be found useful by men of affairs having no special technical knowledge, but who may require from time to time to refer to technical matters in a book of moderate compass, with references to the large standard works for fuller details on special points if required.

To the advanced student the books should be especially valuable. His mind is often crammed with the hard facts and details of his subject which crowd out the power of realizing the industry as a whole. These books are intended to remedy such a state of affairs. While recapitulating the essential basic facts, they will aim at presenting the reality of the living industry. It has long been a drawback of our technical education that the college graduate, on commencing his industrial career, is positively handicapped by his academic knowledge because of his lack of information on current industrial conditions. A book giving a comprehensive survey of the industry can be of very material assistance to the student as an adjunct to his ordinary textbooks, and this is one of the chief objects of the present series. Those actually engaged in the industry who have specialized in rather narrow limits will probably find these books more readable than the larger textbooks when they wish to refresh their memories in regard to branches of the subject with which they are not immediately concerned.

The volume will also serve as a guide to the standard literature of the subject, and prove of value to the consultant, so that, having obtained a comprehensive view of the whole industry, he can go at once to the proper authorities for more elaborate information on special points, and thus save a couple of days spent in hunting through the libraries of scientific societies.

As far as this country is concerned, it is believed that the general scheme of this series of handbooks is unique, and it is confidently hoped that it will supply mental munitions for the coming industrial war. I have been fortunate in securing writers for the different volumes who are specially connected with the several departments of Industrial Chemistry, and trust that the whole series will contribute to the further development of applied chemistry throughout the Empire.

SAMUEL RIDEAL.

AUTHOR'S PREFACE

It has been the author's chief concern that this volume should fulfil its own part in the programme set forth in Dr. Rideal's General Preface.

The leather, glue, and kindred trades have been for many years recognized as chemical industries, but the great development of colloid chemistry in the last few years has given these trades a more definite status as such, and they can now be placed in the category of applied physical chemistry. The time is probably not far distant when some knowledge of pure physical chemistry will be a first essential to students, chemists, chemical engineers, and to all engaged in these industries in supervision, administration, or control. It is hoped that this volume will stimulate the study of these industries from that standpoint.

As the author has previously written upon one of the industries involved herein ("The Manufacture of Leather": Constable & Co.), he has, rather inevitably, found it difficult to avoid altogether his own phraseology. The changes of a decade, however, together with the wider field and newer view-point, have made possible a radical difference of treatment.

The author desires to acknowledge the help he has received from the many books, essays, and researches which are mentioned in the references at the end of each section, especially to Procter's "Principles of Leather Manufacture," and also to thank Dr. Rideal for many useful suggestions. The author would like also to acknowledge here his indebtedness (as well as that of the trade generally) to the work of Dr. J. Gordon Parker, who, through his researches, lectures, and teaching work, has done more than any other man to disseminate a knowledge of practical methods of tanning.

The author's thanks are also due to his brother, Mr. W. Gordon Bennett, M.Sc., A.I.C., M.C., for assistance in proof revision, and to his father, Rev. John Bennett, for some literary criticism.

H. GARNER BENNETT.
BEVERLY, _June_, 1921.

CONTENTS

GENERAL PREFACE

AUTHOR'S PREFACE

CONTENTS

INTRODUCTION

* * * * *

PART I.

HIDES FOR HEAVY LEATHERS.

SECTION

1. THE RAW MATERIAL OF HEAVY LEATHERS

2. THE PREPARATION OF PELT

3. VEGETABLE TANNAGE

4. FINISHING PROCESS

5. SOLE LEATHER

6. BELTING LEATHER

7. HARNESS LEATHER

8. UPPER LEATHERS

9. BAG LEATHER

10. PICKING BAND BUTTS

* * * * *

PART II.

SKINS FOR LIGHT LEATHERS.

1. PRINCIPLES AND GENERAL METHODS OF
LIGHT LEATHER MANUFACTURE

2. GOATSKINS

3. SEALSKINS

4. SHEEPSKINS

5. CALFSKINS

6. JAPANNED AND ENAMELLED LEATHERS

* * * * *

PART III.

CHROME LEATHERS.

1. THE NATURE OF CHROME LEATHERS

2. GENERAL METHODS OF CHROME LEATHER
MANUFACTURE

3. CHROME CALF

4. CHROME GOAT AND SHEEP

5. HEAVY CHROME LEATHERS

* * * * *

PART IV.

MISCELLANEOUS TANNAGES.

1. ALUM TANNAGES

2. FAT TANNAGES

3. OIL TANNAGES

4. FORMALDEHYDE TANNAGE

5. SYNTHETIC TANNING MATERIALS

6. COMBINATION TANNAGES

7. THE EVOLUTION OF THE LEATHER INDUSTRY

* * * * *

PART V.

GELATINE AND GLUE.

1. PROPERTIES OF GELATINE AND GLUE

2. RAW MATERIALS AND PRELIMINARY
TREATMENT

3. EXTRACTION

4. CLARIFICATION AND DECOLORIZATION

5. BLEACHING

6. EVAPORATION

7. COOLING AND DRYING

8. USES OF GELATINE AND GLUE

9. THE EVOLUTION OF THE GELATINE AND
GLUE INDUSTRY

* * * * *

PART VI.

MISCELLANEOUS PROTEINS AND BYE-PRODUCTS.

1. BYE-PRODUCTS OF THE LEATHER TRADES

2. BYE-PRODUCTS OF THE GELATINE AND
GLUE TRADES

3. FOOD PROTEINS

4. MISCELLANEOUS ANIMAL PROTEINS

INDEX

ANIMAL PROTEINS