COMBINATION OF VEGETABLE AND MINERAL TANNAGES.
Early combination tannages — Respective effect of mineral and vegetable tannages — Use of fat-liquor — Action of mineral and vegetable tanning materials on each other — Danish and Swedish glove leathers — Green leathers — Making of fat-liquors — Chrome combinations PAGE [236]
CHAPTER XVIII.
VEGETABLE TANNING MATERIALS.
Distribution of tannin in plants — Structure of barks — Botanical list of important tanning materials PAGE [242]
CHAPTER XIX.
THE CHEMISTRY OF THE TANNINS.
Sources of tannins — General qualities of tannins — Chemical constitution — Catechol- and pyrogallol tannins — Catechins — Tendency of Catechol tannins to darken with light — “Physiological” and “pathological” tannins — Presence of mordant colouring matters PAGE [294]
CHAPTER XX.
THE SAMPLING AND ANALYSIS OF TANNING MATERIALS.