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Mr. H. Wager. 



chlorophyll instead of pyrogallol and potassium hydrate in making 

 quantitative determinations of the amount of oxygen contained in the air. 



The Presence, of Carbon Dioxide is not Necessary for the Pi koto- decomposition 



of Chlorophyll. 



The changes described in the last section are brought about just as rapidly 

 and as completely in the absence of carbon dioxide as when it is present. 



Thus, two flasks were prepared with films of chlorophyll from a petroleum 

 ether solution of grass chlorophyll, as nearly as possible similar to each other. 

 Into one 2 c.c. of distilled water were placed together with a short tube con- 

 taining a stick of potassium hydrate to absorb carbon dioxide, and then 

 tightly corked with a strip of potassium iodide starch paper in the neck of 

 the flask. Into the second flask was placed 2 c.c. of water containing carbon 

 dioxide from a sparklet apparatus, and this was then corked up, also with a 

 strip of potassium iodide starch paper. Both were then exposed to sunlight, 

 and it was found that the bleaching was equally rapid in both cases, that the 

 potassium iodide starch paper was discoloured in both to the same extent, 

 and that the aldehyde in both was similar in amount, so far as could be judged 

 by the depth of colour produced with Schiff s solution. The experiment was 

 tried several times under varying conditions, but the result was always the 

 same, the presence or absence of carbon dioxide made no difference in the 

 effects produced by the light. 



But although carbon dioxide is not necessary for the photo-decomposition 

 of chlorophyll, it is possible that, when present, it may be used up in some 

 way corresponding to the photo-synthesis in the living plant. Experiments 

 conducted with known quantities of carbon dioxide in contact with thin 

 chlorophyll films in long narrow tubes, as used in previous experiments, 

 showed, however, that, whether present in large or in small quantities, the 

 carbon dioxide is apparently not used up in the bleaching of chlorophyll 

 outside the plant. The bleaching takes place quite readily so long as oxygen 

 is present, but the subsequent tests showed no diminution in the amount of 

 carbon dioxide, so far as this could be measured with caustic potash. 



The experiments are not conclusive, however. It is possible that a very 

 small amount of carbon dioxide, too small to be measured quantitatively by 

 the somewhat rough methods at my disposal, may be used up, but the fact 

 that carbon dioxide is certainly not necessary for the bleaching of chlorophyll 

 or the production of aldehyde, and that, so far as my experiments go, 

 no appreciable amount of carbon dioxide is used up even when present 

 in considerable quantities, would seem to indicate that, under the conditions 

 of my experiments, carbon dioxide is not used up by the chlorophyll when 



