86 A RESPIRATION CALORIMETER. 



h = height of barometer (in millimeters), corrected to o. 

 p =ti e m, 



- + L24334 + 0.5091 . 



CALCULATION OF THE TRUE VOLUME OF AIR IN THE CLOSED AIR-CIRCUIT. 



The apparent volumes of air in the different portions of the air- 

 circuit are, as has been stated before, subject to fluctuations, the most 

 noticeable of which is the variation in the quantity of air inclosed in the 

 pans. Volume I, that portion of the air in the air-chamber and the air- 

 pipe and blower and the first water- absorber (see p. 80), is subject to 

 fluctuations which may normally occur inside the respiration chamber, 

 such as interchange of 'air through the food aperture, respiratory loss, 

 etc., in addition to the normal changes as affected by temperature and 

 pressure. The record of the apparent volume of air is given at the 

 right-hand side of the residual sheet (p. 84) . In this particular instance 

 the initial apparent volume of air in section I is 4,909.88 liters, to 

 which a correction of + 0.05 is added for the respiratory loss, 1 thus 

 making a total volume of 4,909.93 liters. This volume of gas is at a 

 temperature (T ) of 20.79 and at a barometric pressure of 755.78 mm. 

 To reduce this volume to that under standard conditions of temperature 

 and pressure the logarithm of the volume is added to the cologarithm of 

 the correction for temperature and the logarithm for pressure, which are 

 taken from tables prepared for convenience. The cologarithm of the 

 correction for the temperature (T ) 20.79 is .96806 and the logarithm 

 for reducing the barometric pressure is .99758. On adding these three 

 factors together it is found that the corrected volume under standard 

 conditions is 4,536.40 liters. This calculation is carried out on the 

 left-hand lower side of the sheet. 



The apparent volume of air in section II, the air-pipe leading from 

 the chamber, the blower, and entrance pipe to the first water-absorber 

 is equal to 6.55 liters measured at a temperature (T x ) of 20.0 and 

 under the same barometric pressure as I. To reduce this volume to 

 standard conditions a similar process is carried out, the calculation 

 being placed immediately beneath the first on the sheet, and we find 

 that the volume 6.55, when reduced to standard conditions, becomes 

 6.07 liters. Since both these volumes contain water vapor, they are 

 added together, their sum giving V^ the volume of the air containing 

 water vapor. 



1 For calculation of respiratory loss for this particular period, see the record sheet 

 on page 64. 



