RES P If! A TION. 9£ 



in excess of C0 2 in the cylinder. At any rate lift the cylinder 

 with the hands in such a way as to hold firmly at the same time 

 the glass tube. Lift it up and down in such a way as to spill a 

 portion of the baryta water over against the wall of the cylinder, 

 ind to dash the potash solution into a spray. Be careful not 

 to toss the mercury out of either arm of the tube. .-■ If the open 

 irm of the' glass tube is closed with the finger (should the 

 apparatus be set up as indicated in fig. 78), the cylinder may 

 be inclined so as to let a portion of the potash solution run, up 

 imong the peas to come directly in contact with t-he C<3\ 

 remaining there. Now rest the cylinder on the table and 

 Dbserve the result. The mercury now, if it did not before, 

 stands higher in the inner arm of the S tube, showing that some 

 :onstituent of the air within the cylinder was consumed during 

 :he formation of the C0 2 . This constituent of the air must be 

 Dxygen, since the carbon can only come from the plant. Where 

 :he baryta water was spilled over an abundance of the white 

 precipitate of the barium carbonate is formed. 



If desired the experiment can be set up as shown in figure 

 78, with the potash solution in the bottom of the cylinder, and 

 :he peas supported on a circular piece of wire netting held in 

 Diace between two small corks inserted in a glass rod. At the 

 :lose of the experiment when the cylinder is being agitated the 

 escaping baryta water forms a large quantity of the whitish 

 precipitate as it washes down the side of the cylinder. 



>eing set free than oxygen is being consumed. This feature of the ex- 

 jeriment demonstrates what is known as intramolecular respiration, a kind 

 )f respiration which can go on independently of the entrance of the oxygen, 

 jee the author's larger " Elementary Botany " page 58. 



