Garhon Dioxide and Chlorophyll. 181 



and partially melting the chlorophyll, the film sometimes becomes 

 more or less distorted. This can largely be avoided by keeping 

 the syphon under cold water flowing from a tap. The syphons 

 remained highly charged with carbon dioxide, but contained no 

 oxygen. 



The films on washing with absolute alcohol gave a yellow solution 

 containing phaeophytin and turning green with zinc acetate. The 

 water was also evaporated to dryness. It was at first clear and 

 colourless, but became faintly brown on evaporating. A trace of 

 solid residue was left by the water from both syphons, which was 

 partly soluble and partly insoluble in water. It averaged under 

 2% of the weight of chlorophyll used. 



If the films are prepared from the first petrol ether separation of 

 chlorophyll without further purification, the water always leaves 

 a larger residue, and that from the syphon exposed to sunlight 

 always contains some reducing sugar. Thus, in one case, the water 

 from the syphon in darkness left a residue containing a little 

 matter soluble in water, and giving a trace of reduction by Feh- 

 ling's test, and a brownish white waxy solid soluble in petrol ether. 

 The residue from the syphon in sunlight contained more matter 

 soluble in water, and gave a strong reduction with Fehling's test. 

 Further tests showed a hexose sugar to be present. The weights 

 were in grams. 



Suiiligrht. Darkness. 



Chlorophyll film .-..-. 0.359 - 0.37 



After 1 week in water + CO^ under pressure - 0.265 - 0.306 



Residue from evaporation of water - - - 0.056 - 0.039 



Total Residue - 0.321 - 0.345 



The same experiment was repeated, using thicker films of chloro- 

 phyll, exposures of four weeks' duration, and evaporating the large 

 bulk of water under reduced pressure and temperature. The 

 water from the sunlight syphon left a brown residue on the sides of 

 the vessel on evaporating, and a gummy residue on the bottom. 

 More than half of the residue was soluble, and it gave the tests 

 for a reducing hexose sugar. The water from the syphon in dark- 

 ness left a brown non-gummy residue of which less than 1/5 was 

 soluble in water, and gave a white flocculent precipitate with Feh- 

 ling's test, but no reduction. No trace of free oxygen was found. 



For deinoiistration purposes the s.vphoii can he filled h.alf way ahove the danger mark and 

 then charged with a sparklet, usinff a control without carbon dioxide. After a week in dark- 

 ness a comparison of the twO syphons forms an admirable lecture demonstration of the action 

 of a solution of carbon dioxide on chlorophyll, the film in the first case beini; yellow, in the 

 latter, green. 



