58 



COMPARISONS OF RESPIRATORY EXCHANGE. 



over the top of the meter to the capillary tube R connected with 

 burettes, 1 and 1, of the gas-analysis apparatus. 



Gas-analysis apparatus. — The general principle of the gas-analysis 

 apparatus is as follows: The gases to be analyzed are automatically 

 collected over acidulated water in two burettes of similar construction 

 in the manner just described. After being measured by leveling at 

 atmospheric pressure, the air is then passed into a 30 per cent solution 

 of caustic-potash in pipettes of special construction containing glass 

 tubes. One of the caustic-potash pipettes is shown in figure 21. 

 Another form of pipette is shown in figure 22. After absorption of 

 the carbon dioxide has taken place, the residual gases are drawn back 

 into two other burettes, where they are again measured at atmospheric 



Fig. 21. 



Fig. 22. 



Fig. 21. — Caustic potash pipette used in the Zuntz-Geppert analysis apparatus. 

 The inside cylinder is filled with glass tubes which give a large surface for absorption of carbon 

 dioxide. The pipette for the absorption of oxygen is of similar construction, but the glass tubes 

 are replaced by stick yellow phosphorus. 



Fig. 22. — Absorption pipette used in the Zuntz-Geppert analysis apparatus. 

 It may contain either caustic potash solution for absorption of carbon dioxide or sodium 

 hydrosulphite for the absorption of oxygen. 



pressure and the temperature of the bath. They are then driven into 

 pipettes containing phosphorus, where the oxygen is absorbed; finally, 

 the remaining gas, or nitrogen plus argon, is measured. 



The general construction of the gas-analysis apparatus may be seen 

 in figure 20. A glass tank filled with water contains 7 burettes. The 

 two outside burettes, 1 and 1 , are designed to measure the collected gas 

 and are therefore graduated in 0.02 c.c. only from —100 to +101 c.c. 

 They are connected at the top by the Y capillary connections, a, a, 

 to the capillary tube R above the apparatus for drawing in the sample, 

 and by the connections, b, b, to the caustic-potash pipettes, H and H. 

 When the sample is drawn from the atmosphere or from the air going 

 through the meter, the clamps at a and a are open, while the clamps at 



