CALCULATION OF RESULTS. 93 



CHECK ON THE COMPUTATION METHOD OF DETERMINING OXYGEN. 



The method of computation outlined on pp. 86-90 gives the amounts 

 of oxygen and nitrogen present in the air at the end of each period ; 

 consequently at the end of any experimental period we can calculate 

 the percentage composition of air free from carbon dioxide and water 

 in the system. If we make such a calculation at the end of a 24-hour 

 period and then make an actual analysis of the air free from carbon 

 dioxide and water at the end of this period, we can obviously compare 

 the computed percentage of nitrogen and oxygen in the air with that 

 actually found by analysis. If the sample for analysis is taken at 7 

 o'clock in the morning, i. <?., when the subject is asleep and the tem- 

 perature condition (thermal gradient) inside the chamber is closely 

 comparable to that of the day before, there is every reason to believe 

 that the computed percentage composition and that actually found will 

 be practically identical. Thus, in the actual experiment recorded on 

 page 84, the percentage of oxygen as calculated was 21.60 and the 

 analysis for that period gave 21.62. In fact, so uniform are these per- 

 centages that any difference in composition is ascribed to a leak of air 

 into or out of the system. 



In case an error has been introduced in some way, it may in many 

 cases be accounted for by careful inspection of the various divisions of 

 the calculations. When desirable, a new nitrogen "baseline" may 

 be determined by using the results of the chemical analysis, after which 

 the calculations are made as before. The increase or decrease in the 

 amount of nitrogen in the new base line is that which has leaked into 

 or out of the system. 



COMPUTATION OF TOTAL CARBON-DIOXIDE AND WATER OUTPUT 

 AND OXYGEN INTAKE. 



Having considered in detail the methods of calculating the residual 

 amounts of carbon dioxide, water, and oxygen in the air, it is evident 

 that it is possible to use the data obtained by such calculations to com- 

 pute the total output of carbon dioxide and water and intake of oxygen 

 during any given period. 



TOTAI, CARBON-DIOXIDE OUTPUT. 



If the total amount of carbon dioxide remaining in the chamber at 

 the end of the period is the same as that at the beginning, obviously 

 the total output during this period is the weight of carbon dioxide ab- 

 sorbed in the carbon- dioxide absorbing system. It is very rare, how- 



