Oxidation of Xanthophyll. 187 



samples of xanthophyll oxidize and bleach much more slowly in 

 light than do impure samples, xanthophyll being less readily oxidiz- 

 able than chlorophyll, and very much less so than carotin. The 

 white waxy solid separated by acetone during purification was ex- 

 posed to light. No production of sugar or formaldehyde could be 

 detected. 



Dry films obtained from the first ether separation yielded small 

 amounts of reducing sugar after photo-oxidation, and this even 

 when the films had been previously well washed with water. The 

 inference might be made that xanthophyll oxidized in the presence 

 of certain associated substances yields sugar, but not when oxidized 

 by itself. The addition of a few particles of magnesium powder re- 

 tards the oxidation of pure xanthophyll greatly, but no sugar or 

 formaldehyde appears. 



To an alcoholic solution of impure " xanthophyll " which yielded 

 sugar readily on photo-oxidation, alcoholic potash was added. A 

 reddish yellow precipitate formed, insoluble in petrol ether, acetone 

 or ether, but dissolving readily in water, and consisting almost 

 wholly of reducing sugar. On now separating the xanthophyll 

 solution with ether, no trace of sugar could be obtained from dry 

 xanthophyll films after photo-oxidation. The impure xanthophyll 

 films evidently contain preformed sugar, possibly held in loose com- 

 bination, so that it is not readily removed by washing with water, 

 but is easily separated from an alcoholic solution by the addition 

 of potash. 



In the purification of the ether solution of xanthophyll by preci- 

 pitation with ether, a large amount of yellow xanthophylloid 

 material remains in solution, and is not precipitated from an 

 acetone solution by methyl alcohol. This forms a yellow oily solid 

 with a low melting point. It is readily soluble in petrol ether. 

 Boiled with water it yields neither formaldehyde nor reducing 

 sugar. Films exposed to sunlight bleach fairly rapidly. They 

 usually yield a trace of acetone (Schiff test, etc.) when previously 

 washed and dried, but give no formaldehyde, Schryvers, Rimmers, 

 and the Schiff, and sulphuric acid tests being all negative. The 

 watery extract from the bleached films when evaporated to dryness 

 dissolved in a little water and filtered, gave in all cases the test 

 for a reducing hexose sugar. 



In a further test, with pure xanthophyll, nearly half a gram was 

 spread as a film inside a large flask exposed to strong sunlight, with 

 a slow current of moist CO.i-free air passing through the flask and 

 then into water in a darkened receiver. The film was wholly 



