390 



Mr. H. Wager. 



and (2) the energy coefficient of the different parts of the spectrum in which 

 the absorption bands appear. Kniep and Minder* have pointed out that the 

 effects produced in photo-synthesis are approximately proportional to the 

 relative energy absorbed. 



The Photo-decomposition Products of Chlorophyll. 



The following experiments show that in the decomposition of chloro- 

 phyll by light two substances are produced, one giving the reactions of an 

 aldehyde and the other an oxidising substance giving reactions with potassium 

 iodide, by which the iodine is set free : — 



Experiment 1 : A piece of paper, tinged with alcoholic solution of 

 chlorophyll, was arranged so that one-half of it was exposed to a good bight, 

 the other being kept dark. The half exposed to the light became bleached, 

 and when placed in Schiffs solution the exposed portion developed a 

 beautiful pink, the unexposed half remaining green with no pink coloration. 



Experiment 2 : If a piece of chlorophyll paper exposed to light as in 

 Experiment 1 is placed in a solution of potassium iodide, the half exposed 

 to the light becomes reddish-blue in colour, due to the liberation of the 

 iodine, which acts upon the starch contained in the paper. The reddish-blue 

 colour is probably due to the action of iodine upon starch in the presence of 

 an excess of potassium iodide, for when the paper is washed in water the 

 reddish-blue colour disappears and is replaced by the ordinary blue starch 

 coloration. 



Similar reactions to those described in these two experiments were found 

 to take place when the paper itself was exposed to light without the chloro- 

 phyll, but the coloration was not so strong in either case. 



Experiment 3 : Two pieces of common note paper, similar to that used in 

 Experiments 1 and 2, were exposed to light in the same way. One was 

 placed in Schiff's solution. The exposed half became distinctly pink. The 

 other was placed in potassium iodide and the exposed half became light 

 brown. This seemed to indicate that the coloration in both cases was due to 

 the paper and not to the chlorophyll. 



Various kinds of paper were then experimented with, and it was found 

 that in all cases a reaction both with Schiff's solution and with potassium 

 iodide occurred, but that in the case of good superfine note paper the 

 reactions were very slight. Accordingly, in all subsequent experiments with 

 chlorophyll-tinged paper, a superfine note paper was used. 



Experiment 4 : A strip of W. H. Smith and Son's superfine cream laid 

 note paper was tinged with chlorophyll and exposed to light as in Experi- 



* ' Zeit. Bot.,' 1909. 



