114 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



an aliquot of that produced inside the chamber. If there were no sub- 

 ject inside the chamber and if outdoor air alone were drawn through 

 this system, there would still be carbon dioxide absorbed in the weigh- 

 ing bottles, for there is a constant amount of carbon dioxide in outdoor 

 air. Some attempts were made to remove this carbon dioxide entering 

 the chamber by blowing the air dehvered by the intake blower (see k, 

 fig. 6) through a large scrubber filled with Hme. This was found to be 

 impracticable, for the absorbing agents best adapted for the removal of 

 carbon dioxide likewise absorbed considerable amounts of water vapor, 

 became pasty, and obstructed the passage of air. Since the carbon 

 dioxide in outdoor air is such a constant quantity, it was believed that 

 use could be made of this constant and a simple correction applied to 

 the carbon dioxide weighed in the bottles L and M. 



While it was stated that the discharge into the sampling cans is 

 approximately 45 to 50 liters per minute, this is not known exactly. 

 Furthermore, the discharge will vary somewhat with the size of aper- 

 ture used in the opening B (figs. 8 and 9). We can, however, meter the 

 air after it has been discharged from either sampling can, passed through 

 the purifying vessels, and is ready to be discharged into the room. 

 This may be done by passing it through the dry gas meter (see fig. 8), 

 a so-called ''3-light gas meter," which has been found satisfactory for 

 the purpose. The meter reads in cubic feet, but metric scales may be 

 obtained, if desired. With the present arrangement of the apparatus, 

 approximately 45 cubic feet of air per half hour are withdrawn from 

 each sampling can. The addition of the meter to the system affects in 

 nowise the discharge into the sampling chamber, meaning simply a 

 slightly greater load for the positive blower, which is already required 

 to force air through two large sulphuric-acid bottles, a system of pipes 

 and valves, a soda-lime bottle, small sulphuric acid bottle, and sodi- 

 umbicarbonate can and, finally, through the meter. 



By reading the meter at the beginning and end of the period, a 

 fairly accurate measure is obtained of the total amount of air in each 

 sample. If uncontaminated outdoor air is passed through the entire 

 apparatus for several hours, a measurement may be obtained of the 

 amount of carbon dioxide per 100 cubic feet of air or per cubic meter. 

 This test has been made repeatedly. While slight fluctuations are 

 found, the values are, on the average, very close to 1.48 grams of carbon 

 dioxide per 100 cubic feet with the particular meter used. The correc- 

 tion for the carbon dioxide in the ingoing air is thus made by simply 

 multiplying the reading obtained from the gas meter in cubic feet by 

 the factor 1.48 grams per 100 cubic feet, and deducting the result from 

 the weight of carbon dioxide absorbed. The remainder corresponds to 

 the carbon dioxide in the sample which was produced by the subject 

 inside the chamber. 



