On the Function of Chlorophyll. 



9 



examination with the polariscope. Accordingly large films on mica and glass 

 sheets were placed vertically in gas cylinders filled with air and kept 

 saturated with water vapour. The lower pointed end of the sheet rested in 

 a small beaker. After some days' exposure to sunlight a few drops of a 

 gummy liquid collected in the beaker. This has a sweetish taste, a faint 

 brown colour, forms a clear solution with water, and gives a strong reduction 

 from Fehling's. The liquid gave the glucosazone test, and with phenylhydrazin, 

 sodium acetate, and alkali, a red colour with a faint violet tinge on warming. 

 The last test must always be done with a blank control, since on long standing 

 a slight red colour may be given in the absence of sugar. Distinct traces of 

 reducing sugar were also given by the watery extracts from the white residues 

 from xanthophyll, but no reduction or a doubtful trace with the watery 

 extract from bleached carotin, bleached in moist C0 2 -free air. No sugar at 

 all could be obtained from similar films kept in darkness. 



Apparently both dextro- and laevo-rotatory sugars are formed. Thus 

 after bleaching 0'72 grm. of chlorophyll in moist CCVfree air, the watery 

 extract gave a doubtful dextro-rotation indicating not more than - 003 grm. 

 of sugar, whereas a Fehling's estimation on Soxhlet's method indicated 

 - 18 grm. of reducing sugar. During the oxidation of xanthophyll films, 

 as much or even more sugar appears to be formed as during the oxidation of 

 chlorophyll. If to an alcoholic solution of xanthophyll half its volume of 

 water is added, and the solution evaporated to dryness after bleaching in 

 the presence or absence of carbon dioxide, the filtered watery extract gives 

 a strong reduction with Fehling's. The bleaching may be hastened by the 

 addition of hydrogen peroxide, but not if a subsequent test is to be made 

 for sugai\ 



The Photo-oxidation of Xanthophyll, C 4 oH 56 02. 



In a preliminary experiment the alcoholic extract from the dried separa- 

 tion residues was used and lined 18 feet of glass tubing. Full bleaching 

 took two days ; moist air free from C0 2 was used. The water in which the 

 gas was collected smelt strongly of formaldehyde and gave a strong pink 

 with decolorised magenta. It contained no carbon dioxide. The dry 

 residues in the tubes weighed 0-427 grm. (from 0'46 grm. of dry xanthophyll). 

 The watery extract from the residue gave a strong reduction with Fehling's 

 test but contained no formaldehyde or other aldehydes. The white waxy 

 residue insoluble in water appeared to resemble the residue from the 

 oxidation of carotin. 



Subsequent tests showed, however, that xanthophyll prepared in this way 

 may contain a trace of sugar and apparently some phytosterin. Accordingly 

 the alcoholic extract was evaporated to dryness, dissolved in a minimum of 



