176 THE DECOMPOSITION OF CARBONIC-ACID GAS. [MEMOIR X. 



Constitution of Gas emitted in Orange and Yellow Light. 



Oxygen 8.0 } f Oxygen 40.4 



Nitrogen 11.8^- or < Nitrogen 59.6 



Carbonic acid.. 0.0 ) ( Carbonic acid. . 00.0 



19.8 100.0 



The gas evolved by the yellow and green rays was 

 next analyzed. Like the former, it underwent no dimi- 

 nution by washing with caustic potash. After this 

 treatment it therefore measured 27.4, and on being ex- 

 amined for oxygen yielded as follows : 



Constitution of Gas emitted in Yellow and Green Light. 



Oxygen 12.5 ~\ /'Oxygen 45.6 



Nitrogen 14.9 > or -(Nitrogen 54.4 



Carbonic acid.. 00. o) ( Carbonic acid .. 00.0 



27.4 100.0 



In explanation of the large and variable amount of 

 nitrogen occurring in these analyses, it will scarcely be 

 necessary to remind the vegetable physiologist that it 

 arises from the mode of conducting the experiment. In 

 order to be absolutely certain that no atmospheric air 

 infilmed the leaves, they were soaked in water, and then 

 when brought into the sunlight the nitrogen which had 

 accumulated in their tissues from incipient decay dif- 

 fused out with the first portions of oxygen. As, there- 

 fore, more and more gas was evolved, the relative amount 

 of the nitrogen diminished. Thus the reason that the 

 third tube appeared to be richer in oxygen than the sec- 

 ond was owing to its containing more gas. Any person, 

 however, who is familiar with the physiological action 

 of leaves will understand these things without any fur- 

 ther explanation. 



UNIVERSITY OF NEW YORK, June 15, 1844. 



