On the Function of Chlorophyll. 



7 



on mica sheets and oxidised rapidly in moist air and sunlight weighed when 

 dried 0478 grm. Possibly some water may also enter into combination. 



The Gaseous Products of the Photo-oxidation of Chlorophyll, Carotin and 



Thin-walled glass tubes 6 feet in length were warmed, and a strong solution 

 of chlorophyll in petrol ether poured in. The heavy vapour falls out of the 

 tube, and with a little practice a film of chlorophyll of even thickness can 

 be left lining the tube. These were exposed to sunlight until bleached 

 (usually 3 to 5 days) in a stream of moist C0 2 -free air, which was led 

 into water through a fine capillary exit tube. In one case where four 

 lengths of six foot tubes were used 1*14 grm. of chlorophyll left 119 grm. 

 of residue, while the water contained no CO2, but smelt strongly of 

 formaldehyde and, by Schiff's test, comparing with standard strengths, 

 contained 0'32 grm. of formaldehyde. On evaporating to dryness, it left a 

 white residue of paraformaldehyde equivalent to - 14 grm. from the total 

 solution. No other aldehyde was present in the solution or in the residue in 

 the tube. 



Similar experiments carried out with tubes lined with pure carotin and 

 xantliophyll films showed that during the photo-oxidation of these substances, 

 no carbon dioxide, but formaldehyde gas is produced, and in the case of 

 xanthophyll possibly a little water vapour is also formed. 



The question at once arises as to whether chlorophyll, like lime-water and 

 feeble alkalies, has the power of polymerising formaldehyde to reducing 

 sugars. If equal quantities of (a) water and (b) a watery solution of form- 

 aldehyde were added to an equal volume of an alcoholic solution of 

 chlorophyll and the mixture exposed to sunlight in the presence of oxygen, 

 (b) turned brown while (a) was still green, but on long exposure (a) became 

 quite pale while (b) was still a darker brown. The liquids were then filtered 

 and evaporated to dryness and gently heated, until in the case of (b) no smell 

 of formaldehyde was perceptible and the loss of weight ceased. The residues 

 and the dry residues from filtering were weighed. 



In both cases the soluble solids gave a strong reduction with Fehling's 

 solution. Alcoholic chlorophyll, however, sometimes contains traces of 

 reducing sugar, and in this experiment carbon dioxide was not excluded. 



Hence, in a second experiment, carbon dioxide was excluded, and of two 



Xanthoph yll. 



A 

 B 



Insoluble residue. Soluble solids. 



.... 0-31 0-81 

 .... 0-425 0-925 



