| FIG. | PAGE | |
| 1. | Curve showing removal of lime by washing | [6] |
| 2. | Cubical “truck” for measuring skin | facing [8] |
| 3. | Puer wheel | " [13] |
| 4. | Front elevation of puer wheel | [13] |
| 5. | End elevation and section of puer wheel | [14] |
| 6. | Sir John Turney’s scudding machine | facing [17] |
| 7. | Curves of ash contents during puering | [38] |
| 8. | Diagram of volumenometer | [62] |
| 9. | " connexions of electrometric apparatus | [76] |
| 10. | Electrometric apparatus | [78] |
| 11. | Apparatus for measuring degree of falling | [83] |
| 12. | Curves obtained by measuring apparatus | [85], [86] |
| 13. | Improved apparatus for measuring degree of falling | [86] |
| 14. | Various forms of bacteria in puer liquors | facing [88] |
| 15. | B. coli commune | " [88] |
| 16. | B. erodiens (Becker) | " [97] |
| 17. | Plate culture from fresh puer | " [97] |
| 18. | " " puer wheel | " [103] |
| 19. | B. putrificus | " [103] |
| 20. | Organisms in pigeon dung, × 1000 | [104] |
| 21. | Pure culture of bacillus (d) from sweated skin | facing [106] |
| 22. | " " " (e) " " | " [106] |
| 23. | B. butyricus (Hueppe) | " [112] |
| 24. | Spirillum volutans (Kutscher), stained to show flagellæ | " [112] |
| 25. | " " " unstained preparation | " [112] |
| 26. | Curves showing rate of hydrolysis | [129] |
| 27. | Organisms in bran drench, × 1000 | [240] |
| 28. | Chains of bran bacteria, × 1000 | [240] |
| 29. | Bran fermentation, advanced stage | [241] |
| 30. | B. furfuris, α | facing [269] |
| 31. | B. furfuris, β | " [269] |
| 32. | Cultures of α in glucose gelatin | [268] |
| 33. | Gas curve (B. furfuris) | [277] |
PREFACE
The present volume is the outcome of a desire to preserve the numerous notes which I have made during over twenty years’ work at the practical and scientific study of bating. It has been my wish to complete the investigation of this important process in leather manufacture, for, as Lord Allerton has paradoxically remarked:[1] “Good leather is made before the skins go into the tan liquor at all,” but owing to circumstances having drawn me more and more to the commercial side of the business, I have been compelled to abandon this project.
When learning the trade as an apprentice every fault in the leather was attributed to this part of the work, and the troubles and miseries of the “puer shop” first caused me to take up the study of puering. I was determined to know the causes underlying the process. Puering is not only a filthy and disgusting operation, but is prejudicial to health, and in the nature of it is attended by more worry and trouble than all the rest of the processes in leather making put together.
By giving a résumé of the work done up to the present time, I hope to be of assistance to the younger generation of Tanning Chemists, to some of whom is reserved the privilege of carrying on the work.
I think it may now be said, at any rate, that the solution of the problem of constructing an artificial bate on scientific principles, which will replace the present crude methods, is well within sight. The principal obstacles are, on the one hand, the inertia of English manufacturers; on the other hand, the class of labour employed in puering is not of the highest order of intelligence. Innovations in most things are resisted, partly because they necessitate changes in the method of working, and partly because of the innate conservatism of human nature. It is certainly a significant fact that although most of the pioneer work on this subject was done in England, the practical side has been taken up in Germany, and by freely spending money on large trials in the works they have enabled the manufacture of artificial bates to be developed on a commercial scale.
In 1886, while studying Chemistry under Professor Frank Clowes, I began to examine microscopically the various liquors of a light leather factory, and more especially the bran drenches. At that time I knew nothing of bacteriology, for the simple reason that little but pathological work in this line was being done in England. Through the kindness of Professor Clowes, I obtained an introduction to Mr. Adrian Brown (now professor at the University of Birmingham), and in his laboratory at Burton-on-Trent I saw the first pure cultivations of Bacterium Aceti which he had isolated, and of which he had completely studied the chemical action.[2] I had there an opportunity of seeing the methods and apparatus employed. I also had the benefit of Mr. Brown’s advice in commencing a systematic study of the process of drenching. Professor Percy Frankland, then at Dundee, advised me further as to the microscope and other matters. My warmest thanks are due to these friends for directing me in the right way.