Nov. 22, 1915 
Improved Respiration Calorimeter 
fore, that the composition of the air in the outgoing pipe fluctuates quite 
uniformly with that of the total air in the chamber. 
Analysis op 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 100 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 yi 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 
