94 A RESPIRATION CALORIMETER. 



ever, that these residual amounts do not vary between the beginning 

 and the end of the period, and consequently it is necessary to make 

 due allowance for such fluctuations. If, for example, at 7 a. m. the 

 residual amount of carbon dioxide is 22.93 grams, and at 9 a. m., at 

 the end of the first two-hour experimental period, the residual amount 

 of carbon dioxide is 35.46 grams, then during this period the subject 

 has eliminated not only the amount of carbon dioxide collected in the 

 absorbing system, but has added to the store in the air in the chamber 

 12.53 grams, and consequently the total output for this period would 

 be w, the weight absorbed in the absorbing system, plus 12.53. Simi- 

 larly, if the amount of carbon dioxide residual in the chamber at n 

 p. m. is 31.26 grams and at i a. m. 24.92 grams, it is apparent that 

 the carbon dioxide absorbed in the absorbing system represents not 

 only that given off by the subject during this period, but also the 

 difference between the residual amount at n p. m. and that at i a. m., 

 namely, 6.34 grams, and consequently the total output of the subject 

 during this period is w, the weight absorbed in the absorbing system, 

 minus 6.34, the amount removed in the residual air. This calculation 

 is carried out for convenience in a table in which the residual amounts, 

 as well as those weighed in the absorbers, are recorded and the proper 

 corrections applied. (See p. 183.) 



TOTAL OUTPUT OF WATER VAPOR. 



The fluctuations in the residual amounts of water vapor affect the 

 total weight of water absorbed in the water- absorber in a manner pre- 

 cisely similar to that in which the residual amounts of carbon dioxide 

 affect the weights of carbon dioxide. If during an experimental 

 period there has been an increase in the amount of water vapor in the 

 air, then the total output of water vapor during this period must be 

 the weight of water collected in the absorbing system plus the increase 

 in the residual amount, and conversely, if there has been a diminution 

 in the residual amount, this diminution must be subtracted from the 

 weight of water in the absorbers to give the true output for the period. 

 In all discussions thus far with regard to water, the assumption has 

 been made that the water exists in the form of water vapor. Since, 

 however, certain parts of the interior of the respiration chamber are 

 frequently at a temperature below the dew-point of the air inside the 

 chamber, there may be a very material condensation of water on these 

 colder parts. When the heat-absorbing system, through which the cold 

 water to bring away the heat passes, is actually below the dew-point, 

 it becomes covered with moisture, and in certain classes of experi- 



