LINNBAN SOCIETY OF LONDON. 9 



By making a film of chlorophyll upon paper and on glass, by 

 floating an alcoholic solution, and allowing it to dry, he was able 

 to bleach a portion under strong sunlight, and covering a portion 

 by black paper ; when tliis was tested by Schiii's solution, the 

 exposed, that is bleached portion, became pink, the unexposed 

 portion showing no colour change. Another experiment was 

 made by subjecting similarly bleached portions of chlorophyll to 

 the action of potassium iodide, when the exposed parts turned 

 reddish blue, in consequence of the liberation of iodine, which 

 acts upon the starch on the paper. 



It was then tried whether the solution of chlorophyll itself gave 

 the reaction. Four test-tubes were partly filled with a solution 

 of chlorophyll in petroleum ether and corked ; two were exposed 

 to light and two kept in the dark : reactions confirmed the previous 

 results. 



These experiments clearly show that the decomposition of 

 chlorophyll is accompanied by the formation of an aldehyde and 

 of something able to oxidize the potassium iodide and to set free 

 the iodine. 



If the (jhlorophyll papers are exposed behind coloured filters, 

 we find that both the aldehyde and the potassium iodide reaction 

 are much stronger in the red than in the blue, and are weakest in 

 the green ; but if the exposure behind the green and blue is pro- 

 longed to 8 or 10 times that of the red, the reaction in the blue 

 becomes as strong as that in the red. 



Instead of alcoholic extract of chlorophyll we may use dried 

 leaves, or chlorophyll expressed from leaves, or layers of Euglena 

 or algae spread over the paper. The reactions also take place 

 inside a leaf, if the bleaching has been efficient. Thus if sun- 

 light is condensed by a lens upon a living leaf of Oxalis Acetosella 

 containing plenty of starch, the chlorophyll is bleached in a small 

 area, and if treated with Schiff's solution, a strong aldehyde 

 reaction results ; if tested with potassium iodide the said area 

 becomes blue. 



It having been stated that formaldehyde is produced when 

 chlorophyll is exposed to sunlight in the presence of carbon 

 dioxide, an attempt was made to determine whether such was 

 the case in the present series of experiments ; but the author 

 was not able to satisfy himself on this point, though several of 

 the tests succeeded even with so small an amount as one-millionth 

 of formaldehyde. Hydrogen peroxide had been suggested as the 

 gaseous oxidising compound of chlorophyll, but the result of many 

 varied tests showed that this was not so. 



Further experiments were detailed, as those on chlorophyll in 

 Laminaria: that photo-decomposition of chlorophyll takes place 

 only in the presence of oxygen ; that carbon dioxide need not be 

 present to cause photo-decomposition of chlorophyll ; and the 

 action of light upon the green and yellow pigments of chloro- 

 phyll — the yellow pigment bleached rapidly, the green much more 

 slowly. 



