VIII] . AROMATIC COMPOUNDS 113 



It occurs, either free, or combined with various sugars (glucose, 

 rhamnose) as glucosides, in many plants, as for instance the following : 

 in the bark of species of Oak (Quercus), in berries of species of Buck- 

 thorn (Rhamnus), in flowers of Wallflower (Gheiranthns Gheiri), Haw- 

 thorn (Grataegus Oxyacaniha) (Perkin and Hummel, 16), Pansy {Viola 

 tricolor) (Perkin, 13) and species of Narcissus : in leaves of Ling {Galluna 

 erica) (Perkin, 17), and the outer scale leaves of Onion bulbs (Perkin 

 and Hummel, 15). 



Expt. 110. Preparation of a glucoside of quercetin fro7n flowers of either a species 

 of Narcissus or the Wallflower (Cheiranthus Cheiri). The most suitable species of 

 Narcissus is N. Tazetta, but N. incomparabilis or any of the common yellow trumpet 

 varieties such as the Daffodil {N. Pseudo-Narcissus) can be used. Take about 50 

 flowers of Narcissus Tazetta or about 20 gms. of petals of the Wallflower of either 

 the brown or the yellow variety. The brown colour is due to a mixture of yellow 

 plastid and of soluble purple (anthocyan) pigment in the sap. Pound the flowers in a 

 mortar and then extract in a flask with boiling alcohol. Filter off the alcoholic 

 extract and evaporate to dryness on a water-bath. Then add a little water and ether 

 to the residue and transfer the whole to a separating funnel. The ether takes up 

 the yellow plastid pigments, but the flavone and, in the case of the brown Wallflower, 

 the anthocyan pigment remain in the water. Very soon, however, at the plane of 

 separation of the liquids, the glucoside separates out as a crystalline deposit. This 

 can be filtered off ; with a dilute solution in alcohol make the following tests : 



(a) Add a little alkali. The yellow colour is intensified, but the intensification 

 disappears on adding acid. 



(6) Add a little lead acetate solution. An orange precipitate of the lead salt is 

 formed. 



(c) Add a little ferric chloride solution. A green coloration is produced. 



{d) Heat some of the alcoholic solution on a water-bath, acidify with strong 

 hydrochloric acid and add zinc dust. A pink or magenta colour is produced 

 (see p. 121). 



Kaempferol occurs in the flowers of a species of Larkspur {Delphi- 

 nium consolida) (Perkin and Wilkinson, 19) and Pr units (Perkin and 

 Phipps, 18) and in the leaves or flowers of several other plants. It has 

 the formula: 



HO 



^^^""^ 



\/ 



■rC 



OH 



HO ^° 



\„^°" 



O. 



