12 CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



but with the attempts to measure the oxygen it was found that the large 

 volume of residual air inside the chamber, amounting to some 4,500 liters, 

 made possible very considerable errors in this determination, for, obviously, 

 the subject could draw upon the oxygen residual in the air of the chamber, 

 nearly 1,000 liters, as well as upon the oxygen furnished from outside 

 sources. The result was that a very careful analysis of the residual air 



Fig. 8. — Vertical cross-section of chair calorimeter, showing part of 

 rear of calorimeter and structural-steel frame. N, cross-section 

 of bottom horizontal channel supporting asbestos floor J; H, H, 

 upright channels (at the right is a side upright channel and to 

 the left of this is an upright rear channel) ; M, horizontal 3-inch 

 channel supporting calorimeter; Zn, zinc wall; Cu, copper wall; 

 J, insulating asbestos. 



must be made frequently in order to insure that the increase or decrease in 

 the amount of oxygen residual in the air of the chamber was known accu- 

 rately at the end of each period. Analysis of this large volume of air could 

 be made with considerable accuracy, but in order to calculate the exact 

 total of oxygen residual in the air it was necessary to know the total volume 

 of air inside the chamber under standard conditions. This necessitated, 

 therefore, a careful measurement of temperature and pressure, and while 

 the barometric pressure could be measured with a high degree of accuracy, 



