The xanthophyll group of yellow colouring matters

Abstract

The group under consideration comprises those colouring matters occurring in flowers, leaves, fruits, etc., which are insoluble in water but soluble in alcohol, ether, carbon-bisulphide and other organic solvents, to which collectively the name of xanthophyll has been applied. It is to these colouring matters that the characteristic yellow colour of flowers, autumnal leaves and fruits in the majority of cases is due. There are, however, present, varying in amount but generally in considerably less relative quantity, other yellow colouring matters which are soluble in water and alcohol, sparingly soluble in ether but insoluble in carbon-bisulphide; they, however, absorb the violet and ultra-violet rays without giving any absorption bands, whereas the members of the xanthophyll group transmit the ultra-violet rays and give definite absorption bands in the less refrangible region of the spectrum, whereby they may be distinguished from one another, and which is their chief characteristic feature.