CONTENTS xi 



PAGE 



Pyrocatechol tannins 213 



Catechu tannic acid 213 



Catechin 214 



Quercitannic acid 214 



Physiological significance of tannins ....... 214 



SECTION v.— PIGMENTS 222 



Chlorophyll 222 



Extraction ........... 227 



Crystalline and amorphous chloropyll ...... 229 



Constitution . . . . . . . . . . .231 



Yellow pigments accompanying chlorophyll 236 



Carotin 236 



Xanthophyll ........... 237 



Flavones and Xanthones 238 



Yellow pigments derived from flavone ...... 239 



Yellow pigments derived from xanthone ..... 240 



Anthocyanin, Phycoerythrin and Phycophaein 242 



Anthocyanin 242 



Properties ........... 244 



Reactions 247 



Physiological significance 247 



Phycoerythrin 249 



Preparation ........... 249 



Reactions 250 



Phycophaein 251 



SECTION VI.— NITROGEN BASES 253 



Alkaloids ............ 255 



Classification 256 



Properties 259 



Reactions ........... 260 



Isolation 261 



Origin of alkaloids in the plant 262 



Ptomaines 264 



Purine bases 266 



Physiological significance of nitrogen bases ...... 270 



SECTION VII.— COLLOIDS 



273 



Properties 274 



Diffusibility 274 



Optical properties . . . 275 



Change of state or gel formation 277 



Protective power 281 



Classification of Colloids 281 



Properties of suspensoids 282 



Properties of emulsoids ......... 283 



The nature of gels . . 284 



Adsorption 285 



Enzyme action of colloids 287 



SECTION VIII.— PROTEINS 291 



General properties .......... 292 



Microchemical reactions 208 



