Oxidation of Chlorophyll. 183 



extract of chlorophyll always bleach more rapidly in light than do 

 pure preparations of chlorophyll. No evidence could be obtained 

 of the existence of any special oxidase enzymes in the impure films, 

 but these always yield small amounts of reducing hexose sugar, even 

 if previously well washed with water prior to photo-oxidation, 

 whereas fully purified chlorophyll yields no sugar on photo -oxida- 

 tion. In one test experiment, a sample of pure chlorophyll was 

 prepared as described by Willstatter and Hiig (Annalen, 1911, p. 

 177). Two films of it were prepared each in a large bulb tube, 

 containing dry CO^ free air. After a week's exposure to sunlight, 

 no further bleaching took place. The volume of air decreased by 

 14.6%, a small amount of water appeared, but no reducing sugar. 

 After shaking with water and filtering, the latter gave Riminis, 

 Schryver's, Schiff test, and the Schiff and sulphuric acid tests for 

 formaldehyde. The amount present was, however, distinctly less 

 than when a current of air was passed over long tubular films 

 exposed to sunlight, and then led into water, as described in the 

 previous paper. 



The changes which chlorophyll undergoes during photo-oxida- 

 tion in dead tissues are not necessarily precisely similar to those 

 taking place after its extraction and purification. It has, how- 

 ever already been shown (Proc. Royal Society B., 1908, 80, 30) that 

 formaldehyde is produced in green leaves by the photo. -oxidation 

 of chlorophyll after death, and in the absence of carbon dioxide.^ 

 Green grass leaves were boiled and then dried in a strong press re- 

 peatedly until they yielded no trace of reducing sugar. The leaves 

 were then spread flat on glass plates, and held in position by silk 

 threads. The plates were placed in large glass vessels — (a) contain- 

 ing COg free air, (b) with COj present, (c) ordinary air. The vessels 

 (a) and (b) were exposed to sunlight until the leaves were bleached, 

 (c) was kept in darkness. The air in all three was kept moist. The 

 leaves were then extracted with boiling water, which was concen- 

 trated, filtered and tested. Both (a) and (b) yielded small amounts 

 of reducing hexose sugar, while (c) yielded none. Apparently the 

 post mortem photo-oxidation of chlorophyll and its companion 

 substances can increase the extractable sugar content of drying hay 

 in the same way that photo-oxidation causes sugar to separate 

 from an impure chlorophyll film. 



1 Further confirmation of this has recently been g\vtn l).v Osterho it, see n. se:' 

 p. 68. See also Schr.wer, Proc. Roy. Soc. London, B., 1910, 82, 226. 



