Nov. 22. 1915 Improved Respiration Calorimeter 3 1 1 



fore, that the composition of the air in the outgoing pipe fluctuates quite 

 uniformly with that of the total air in the chamber. 



Analysis of Sample for Water Vapor and Carbon Dioxid 



For the determination of the amounts of moisture and carbon dioxid 

 residual in the chamber at the end of each period, a portion of the air 

 coming from the chamber at that time is shunted from the main current 

 through a petcock in the air pipe at a point between the rotary pump 

 and the first sulphuric-acid bottle, and is passed first through a small 

 purifying system and then through an accurate gas meter, which rests 

 on the top shelf of the table for the large absorbers, as seen in Plate 

 XXXVI, figure 2. The air leaving the meter is passed through sul- 

 phuric acid to remove the water vapor taken up by it in passing through 

 the meter, and is then returned to the main current flowing from the 

 large absorbers to the chamber. The water-vapor absorbers of the 

 small train are specially devised, somewhat resembling those of the large 

 train, but of such size that they may be weighed on an analytical balance 

 (PI. XXXIII, fig. 2). A 4-inch U tube with side outlets and well-ground 

 glass stoppers makes a serviceable soda-lime container. A train consist- 

 ing of one acid bottle, one U tube, and another acid bottle very efficiently 

 removes all water vapor and carbon dioxid from the air passing through 

 it at a rate of about 3 liters per minute. 



The small absorbers are weighed on an analytical balance to an accu- 

 racy of 0.1 mgm., each unit, when charged, weighing less than loo gms. 

 The increase in the weights of the units shows the quantities of water 

 vapor and carbon dioxid in a given volume of the air. Usually 10 or 20 

 liters of air, as indicated by the meter, are passed through the train, the 

 actual volume being ascertained by correcting the meter reading, when 

 necessary, for the calibration of the meter and for the temperature and 

 barometric pressure of the air passing through it. 



Analysis of Sample for Oxygen 



For the determination of the proportion of oxygen in the residual air 

 a small sample, about >2 liter, is taken from the returning air in the pipe 

 between the large purifying system and the respiration chamber, where 

 it is free from water vapor and carbon dioxid. In Plate XXXVI, 

 figure 2, a rubber bag for holding the sample is seen hanging from an 

 outlet in the air pipe at the end of the absorber table. A modified 

 Haldane burette is used in the determination, the oxygen being absorbed 

 by a potassium-pyrogallate solution in a Hempel pipette. 



Computation of Volumes of Gases Present 



The actual determination of the proportion of oxygen in the air is not 

 necessary at the end of each period. The volume of oxygen present in 

 the air of the chamber may be computed by subtracting from the actual 



