182 Alfred J. Ewart : 



The film from sunlight was in the thinner parts nearly colour- 

 less, and in the thicker parts more brown than yellow. It contained 

 less phaeophytin than the films kept in darkness. The weights 

 were — 



Chlorophyll film - . - 

 Total film residue after 4 weeks 

 Total water residue 



Total 



From the above it would appear that in sunlight and COg, chloro- 

 phyll decomposes slightly more than in darkness, that a little for- 

 maldehyde or other volatile product is formed, and that if any 

 oxygen is formed, it is not set free, but oxidises the phaeophytin. 

 The action is not continuous as in the plant, since there is no re- 

 construction of the chlorophyll. 



It appears, further, that the sugar formed in the plant remains 

 at first in loose combination with the chlorophyll, and follows it 

 into the petrol ether and other solvents, and that it is only sepa- 

 rated from the chlorophyll when this is purified by precipitation. 



If pure chlorophyll films are dusted over with zinc dust, they 

 remain green in contact with a solution of carbon dioxide in water 

 indefinitely, and even after a week's exposure to sunlight only show 

 a slight fading on the more exposed side. On dissolving the films 

 the solution shows the same absorption bands as chlorophyll, but 

 the solubility is altered. 



On incinerating, the ash of the green pigment was found to consist 

 of zinc oxide, and not of magnesium oxide. It evidently consisted 

 of the salt of zinc with phaeophytin, described by Willstatter and 

 Hocheder (Annalen der Chemie, 1907, 353, p. 205), which closely 

 resembles chlorophyll. Evidently in the presence of a saturated 

 solution of carbon dioxide in water, zinc will displace the mag- 

 nesium of chlorophyll. In the previous paper I had described some 

 results which seemed to show that with the aid of zinc dust and in 

 the presence of carbon dioxide a reconstitution of chlorophyll was 

 possible from the products of its decomposition. What really hap- 

 pened was that the zinc salt of phaeophytin was formed, which 

 closely resembles chlorophyll, and is easily mistaken for it. This 

 zinc salt appears to be more resistant to acids and to photo. -oxida- 

 tion, and to be more stable than natural chlorophyll. 



It is worthy of note that impure chlorophyll films prepared 

 directly from the first petrol ether separation of an alcoholic 



