Nov. 22. 191S 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. Each 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 from 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- 



