CH. ii] timiriazeff's eudiometer. 45 



may be obtained with the Winkler-Hempel apparatus, — 

 described in exp. 4, p. 6. 



The jar, J, fig. 3, containing leaves is filled with air 

 containing about 8 7o of COg : the exact proportion is of 

 no importance, but it must be accurately determined at 

 the beginning of the experiment. The bent tube t serves 

 to draw off a sample of the gas in the jar /, and as it is 

 drawn off, the water flows through the tube I from the 

 beaker o outside, into the second vessel inside i. The 

 tubes t and I are now clamped, and the apparatus exposed 

 to bright light for 4 or 5 hours when a fresh sample of gas 

 is drawn off and analysed. The water introduced absorbs 

 some of the CO2 and causes an error, which however is not 

 so serious as to interfere with the results for demonstra- 

 tion purposes. 



(52) Timiriazeff's Eudiometer'^. 



For the analysis of gas given off from w^ater plants 

 we use Timiriazeff's Micro-eudiometer arranged for the 

 analysis of larger quantities of gas, e.g. for 0"5 c.c. instead 

 of " a bubble no bigger than a pin's head." 



The apparatus (shown in fig. 10) consists of three parts 

 — the eudiometer E, the pipette P, and the carrier C. 



The eudiometer is a tube of 5 mm. internal diameter 

 graduated in O'Ol c.c. : the upper end is covered by a 

 short (25 mm.) length of rubber tube through which 

 passes a glass rod R serving as a piston. The lower end 

 of E is enlarged into a small funnel F to facilitate the 

 entrance of the gas to be analysed. The carrier C consists 



1 Ann. Sc. Nat. S6rie vii. 1885, vol. 11. p. 112. 



