t 

 THE RESPIRATION APPARATUS. 55 



to the mark G. The volume of gas thus returned to the burette must 

 be supplemented by a volume to be delivered from the burette B, before 

 the gas can be read on B 2 . The reservoir Rj is lowered until the level 

 of the liquid in R : and B : are the same. The reading on B, is then 

 carefully noted. On raising R! and carefully opening stopcock C pure 

 nitrogen can be driven over into B. 2 . It is necessary, however, that in 

 this case the reservoir R 2 should be at or about the level shown in 

 figure 1 6. As soon as sufficient nitrogen has been forced into B 2 to 

 bring the water level well on the graduated portion of the burette the 

 stopcock C is closed. After again adjusting the water levels in Rj and 

 BI, the reading of the gas remaining in B, is made and the difference in 

 volume subtracted from the final reading on B 2 . The final readings of 

 volume and temperature are, of course, not taken until the water has 

 settled and drained down the sides of the burette. 



A specimen analysis of a sample of the air taken from the respiration 

 chamber is given below as illustrating the methods of analysis. The 

 sample of air was drawn at 7 a. m. on April 29, 1904. The reading on 

 B, was 99.25 cc. -(- 0.51 = 99.76 cc. The initial temperature was 18.64; 

 the corrected barometer reading was 753.29 mm. After absorbing the 

 oxygen the gas was run back into B 2 and nitrogen from Bj added to 

 this volume. The first reading on E 1 was 19.00, the second 5.47, in- 

 dicating that 13.53 cc. of nitrogen had been added to the volume of 

 the gas in B 2 . The final reading on B, was 93.89. On deducting the 

 J-S-SS cc - f nitrogen that were added from B 1} the corrected volume of 

 gas measured in B 2 was 80.36. There still remained, however, the 

 constant volume 0.34, which should be added for the gas remaining in 

 the stopcock and connection to graduation point G. The final result, 

 then, is 80.36 + 0.34 = 80.70. The change in temperature amounted 

 to 0.09, the initial temperature being 18.64 an( i the final I 8.73. In 

 increasing its temperature the gas has expanded and the tension of 

 aqueous vapor has increased slightly ; consequently it is necessary to 

 take into consideration its effect on the tension of the gas in the burette. 

 The tension of aqueous vapor at 18.64 is equal to 15.96 mm. of mer- 

 cury. This, subtracted from the barometric reading, 753.29, gives the 

 reduced pressure as 737.33 mm. 



The tension of aqueous vapor at 18.73 is J 6.o5 mm. As there was 

 no noticeable change in the barometric pressure, this tension is deducted 

 from the original barometric pressure, i. <?., 753.29, and the resulting 

 pressure is equal to 753.29 16.05 = 737- 2 4 mm - Therefore 99.76 cc. 

 of air at 18.64 and 737.33 mm. pressure yield 80.70 cc. of nitrogen at 

 18.73 and 737.24 mm. 



On reducing both these gas volumes to standard conditions of tem- 

 perature and pressure we find that this particular sample of air contains 



