CH. l] RESPIRATION. 9 



the graduations on 6r, after bringing the water in the two 

 tubes to one level. To absorb the C0 2 , H is connected 

 with the india-rubber tubing C of the absorption pipette 

 (fig. 4). F is raised, and L and the clamp C opened. The 

 gas is thus forced over into D, where it is retained for a 

 minute or so and gently shaken in contact with the KHO, 

 the clamp C and stop-cock L being closed meanwhile. 

 When absorption is believed to be complete the gas is 

 sucked back into G (fig. 5) by lowering F, C and L being 

 open. L is then closed and G and F brought to a level 

 so that the diminished volume of gas can be again read 

 off. The difference gives the amount of CO 2 originally 

 present. To make sure of complete absorption the gas 

 may be again passed into D, shaken and returned, when 

 it should show no further reduction in volume. 



When any potash is sucked back into G along with 

 the gas the tubes must be carefully washed clean before 

 being used for another sample of gas. 



(5) Bonnier- Man gin apparatus 1 . 



This instrument may be used for determining the 

 amount of CO 2 produced in a given time by a known 

 amount of germinating seeds. It gives the advantage 

 of analysing small volumes of gas e.g. 0'3 c.c. It resembles 

 Timiriazeff's eudiometer (see Exp. 52) and the Winkler- 

 Hempel apparatus (see Exp. 4) in requiring no correction 

 for temperature or pressure, and since mercury is the fluid 

 employed it can be satisfactorily used for the estimation 



1 Full instructions for the use of the apparatus are given by Aubert, 

 Revue generale de botanique, T. iii. : a copy of the paper is sent out with 

 the instrument. 



