80 A RESPIRATION CALORIMETER. 



weighing the carbon-dioxide absorbers. No notice was therefore taken 

 of the change in the amount of residual carbon dioxide. Theoret- 

 ically, of course, this should be taken into consideration, although the 

 ultimate result in 24 hours is compensating and no error finally results. 

 In the first morning period, i. e., from 7 a. m. to 9 a. m., the amount 

 of carbon dioxide collected in the absorbers, especially in a work ex- 

 periment, is considerably less than that actually eliminated. On the 

 other hand, in the later periods of the day the amount of carbon 

 dioxide thus absorbed is more than that actually eliminated during a 

 given period. 



A similar criticism applies to the use without correction of the 

 weight of oxygen admitted for the variations in the residual amount 

 of oxygen. As regards water vapor, no changes in residual amounts 

 that could materially affect this calculation are possible. 



In general, however, the actual correction for respiratory loss is not 

 very large, and, while the residual amounts of carbon dioxide and 

 oxygen should theoretically be taken into consideration in the cal- 

 culation, it would be rather difficult and somewhat costly to carry 

 through a preliminary calculation to determine the total amount of 

 residual carbon dioxide and then recalculate the experiment, allowing 

 exactly for the respiratory loss. 



SUBDIVISION OF AIR VOLUMES. 



In calculating the true volume of gases in the different parts of the 

 system, it is necessary to take into consideration the apparent volume as 

 shown in the preceding section of this report, the barometric pressure, 

 and the temperature. Of these three factors, the apparent volumes 

 are determined by measurement, and the barometric pressure is that 

 of the atmosphere, since the volumes of gas are measured when the 

 blower is stopped, and due corrections are made for that small propor- 

 tion of the total air which is confined in the first water-absorber and 

 the carbon-dioxide absorbers. The temperature measurements are 

 made in two places first, that of the large volume of air in the res- 

 piration chamber, and second, that of the exterior portions of the 

 apparatus. For calculating the true volume of air, four subdivisions 

 of the air volume are made on the basis of differences in composition 

 or temperature as follows : 



I. The volume of air in the chamber. 



II. The air in the pipe from the chamber to the absorbing system, 

 including the blower and the entrance pipe of the first water-absorber- 



III. The volume of air from the bottom of the first water-absorber 

 to the entrance end of the second carbon-dioxide absorber. 



