258 RESPIRATION, FERMENTATION AND DIGESTION 



ing the seeds has been calculated the exact amount of the gases 

 interchanged may be found. The Bonnier and Mangin apparatus 

 may be used instead of the one referred to above. 



327. Estimation of Atmospheric Gases with Bonnier and Mangin 

 Apparatus. Fill a test-tube with mercury and support mouth 

 downward in a small receiver full of mercury (Fig. 127, /). Con- 

 nect a short bent tube with the outlet of the receiver containing 

 the germinating seeds. Run water into the receiver displacing the 

 air, and as soon as that in the outlet tubes has been thrown out run 

 the tip under the rim of the inverted test-tube and allow a few cc. 

 to escape into it. Close the receiver and transfer the test-tube to 



Fig. 127. Apparatus for determination of atmospheric gases designed by Bonnier 

 and Mangin. a, wheel with handle attached to a piston with threads on its surface : 

 the inner end of the piston projects into the cavity of a cylinder b, which is filled with 

 mercury ; revolutions of the piston cause movements out of the cylinder into the 

 graduated glass tube fg, and vice versa, c, metallic fitting, connecting graduated 

 tube with cylinder, d, bulb in glass tube, f, portion of glass tube, calibrated, g, 

 U-shaped portion of glass tube the outer end of which lies underneath the surface of 

 the mercury in the vessel h. m, showing method of placing test-tube containing gas to 

 allow the gas to be drawn into the graduated tube, n, showing the portion of the 

 graduated tube which should be filled by the gas in a test. /, small receiver suitable 

 for containing the solution used in absorbing gases. A similar form is suitable for mer- 

 cury over which the test-tubes may be filled with gas from the bell-jar containing the 

 plant. After Belzung 



the bowl of the measuring apparatus, holding the thumb over the 

 mouth of the inverted tube enclosing a layer of mercury and the 

 gas to be tested. Press the test-tube downward over the capillary 



