42 



GAS ANALYSIS. 



[CH. II 



14 — 15 mm. in diameter, T (fig. 9); above this part the 

 tube is blown into a balloon and ends above in a narrow 

 tube B with flat ground edges. The whole tube contains 

 about 120 c.c. The leaf to be experimented on is rolled 

 into a cylinder and gently pushed up 

 the tube with a wooden rod until it 

 reaches the wide part of the tube, where 

 it unfolds of itself. After the experi- 

 ment is over, the leaf is to be removed 

 by means of a piece of thin iron wire, 

 W, attached to the stalk before the leaf 

 was inserted. During the experiment 

 the wire should be attached outside the 

 tube by an elastic band E. The tube 

 is fixed vertically in a glass beaker, 

 H^ having upright sides and containing 

 mercury, and a drop or two (0"2 — 0*3 c.c.) 

 of water is placed above the mercury 

 column in the calibrated tube to protect 

 the leaf from mercury fumes. By apply- 

 ing suction at B the mercury column 

 is raised to a desired height. The 

 suction is best applied through a wash- 

 ing bottle containing water, so that 

 the breath of the operator may not 

 come directly in communication with 

 the air in the gas-tube. An india- 

 rubber tube fitting over B serves to 

 connect with the washing bottle, and 

 also to close the tube when desired. When the mercury 



Fig. 9. Exp. 50. 



Copied from Pfeffer 



loc. cit. 



