The Intake of Carbon 219 



vigorously for several minutes, cork, and let stand until the two 

 areas are constant. Describe the separation phenomena. 



If a spectroscope is to be employed, as suggested in the next 

 experiment, larger quantities of the materials may be used in the 

 bottle, and a more complete layering effected by the addition of 

 a small amount of water. In that case the two solutions are 

 separated by pipetting or by the burette ; each is again washed 

 with the opposite solvent, again separated, and subsequently 

 employed for a determination of the absorption bands of each. 



Spectroscopic examination of chlorophyll. If practicable, 

 make, under standard conditions, a careful spectroscopic exami- 

 nation of a chlorophyll solution of different strengths ; also of 

 the constituents dissolved respectively in benzole and alcohol, 

 resulting from the separation of the pigments above. Make a 

 comparison with the living leaf, the latter preferably exhausted 

 of air and injected with water, by being placed in a vessel of water 

 under the exhaust or filter pump. 



Evolution of gas during photosynthesis. Notice that when a 

 mass of alga or aquatic moss, Elodea, or other water-weed is 

 placed in spring water and exposed to the light, bubbles of gas 

 promptly accumulate, especially from cut surfaces of the larger 

 plants, and rise to the surface. No such evolution of bubbbs 

 takes place with control plants in the dark, although a few bubbles 

 may, of course, gradually form on the walls of vessels or of sub- 

 mersed plants standing for some time exposed to temperature 

 changes. 



Quantity and nature of gas released in photosynthesis. - Ma- 

 terials : fresh shoots of a water plant, Elodea or Cabomba ; 

 a battery jar, at least 9x5 inches, filled with spring water, or 

 with water into which a small amount of CO 2 has been led ; a 

 funnel not more than 3 inches in diameter, with short stem ; 

 a 4-inch test-tube, preferably graduated, and two pieces of glass 

 tubing of same diameter, one about 5 inches long, and the other 

 1 inch ; black rubber tubing suitable for attachment to the pre- 

 ceding; 2 pinch-cocks; a ring stand with clamp; and a netted 

 wire basket 3 inches high, with cross rods at the top to support 

 the funnel, all metal being paraffined. 



