NOV. 22, 1915 
Improved Respiration Calorimeter 
307 
pumice stone, which effectually prevent visible particles of acid from 
being spattered into the exit tube or carried into it by the air current. 
During several years' use these bottles have proved to be very satis¬ 
factory. Before they were used in experiments a large number of tests 
of their efficiency were made, in which air was passed at various rates 
up to 80 liters per minute through three of the bottles in series, the first 
one containing water, in which the air became very moist, and the other 
two charged with acid. It was found that the moist air leaving the 
first bottle could be passed through the acid in the second bottle until it 
was diluted to nearly twice its bulk before the third bottle increased 
appreciably in weight. No gain in weight was ever observed in a third 
acid bottle included in the series in some of the tests. In many of these 
tests the water vapor in the air leaving the water bottle was very nearly 
saturated at the temperature of the laboratory. These conditions imposed 
as severe a test on the capacity of the device to remove all moisture 
from the air flowing through it as any that would occur in respiration 
experiments. 
In practice, two bottles are used in series and the first one is recharged 
when the acid in it has become diluted to a volume indicated by a mark 
on the bottle, in which case 750 c. c. of acid have usually absorbed 500 
to 600 c. c. of water. Bach bottle with its charge of acid weighs not far 
from 2,600 gm. The two acid bottles will stand side by side on the 
pan of the large sensitive balance, and are weighed together to an accu¬ 
racy of 0.1 gm. The increase in the weight of these two absorbers in a 
given period shows how much water vapor has been carried out of the 
chamber during the period. 
Removing Carbon Dioxid prom the Air 
The air from the acid bottles passes next through bottles containing 
soda lime (a mixture of caustic soda and quicklime), which deprives it 
of carbon dioxid. The soda-lime container that has been in use for 
several years consists of an ordinary wide-mouth bottle about 25 cm. 
in height and 13 cm. in diameter. The mouth of the bottle is closed 
with a No. 12 rubber stopper, through which pass an inlet tube and an 
outlet tube of brass pipe, with a bore of 15 mm. The inlet tube extends 
nearly to the bottom of the bottle. The lower opening of this tube is 
protected with brass wire gauze to prevent particles of soda lime from 
entering it. The outlet tube extends outward from the under side of 
the stopper. When the stopper is tightly sealed and bound in place, 
soda lime in particles about the size of a dried pea or smaller is intro¬ 
duced through the outlet tube until the bottle is filled quite near to the 
top. Each bottle when thus charged contains a little over 2 kgm. of 
soda lime and weighs about 4 kgm. 
Two of these bottles are used in series, and each one is kept in use 
until the appearance of the soda lime indicates that it is no longer effi- 
