MEMOIR X.] THE DECOMPOSITION OF CARBONIC-ACID GAS. }f5 



same size and volume were placed in each tube. This 

 grass had been kept for two days in the dark in a bottle 

 filled with carbonated water. During this time the film 

 of air which envelops all new leaves was removed, the 

 grass became perfectly free from all adhering gaseous 

 matter, and when in the carbonated water exhibited a 

 dark-green aspect. 



I have previously found that leaves thus soaked emit 

 under the influence of light a larger amount of nitrogen 

 than usual ; this comes from the incipient decay of some 

 of their nitrogenized constituents. When under these 

 circumstances they are placed in the sunshine, this nitro- 

 gen comes off along with the gas liberated from the car- 

 bonic acid. 



In the experiment I am now relating, a tube arranged 

 like one of the foregoing five evolved in the open sun- 

 shine a certain volume of gas which was composed of 



Oxygen 41 ~\ 



Nitrogen 59 '- 100 



Carbonic acid 00 ) 



The five tubes were placed in the spectrum in the fol- 

 lowing colors, and emitted the quantities of gas repre- 

 sented in the following table : 



The gas in tube 2, which had been in the orange and 

 yellow ray, was then washed with a solution of caustic 

 potassa. After this it still measured 19.8. It contained, 

 therefore, no perceptible quantity of carbonic acid. It 

 was next examined for oxygen, and with the following 

 result : 



