TECHNIQUE FOR METABOLISM DURING REST. 115 



TEST OF ALIQUOTING DEVICE. 



While the calculation of the several areas of the three discharge 

 openings from the wind chest gives an approximate estimate of the rela- 

 tive amount of air that will be discharged, on the fundamental assump- 

 tion that the air thus expelled will be directly proportional to the area 

 of a cross-section of the orifice, nevertheless in any accurate use of the 

 apparatus, such a gross assumption can not go unchallenged. It 

 accordingly became necessary from the earliest development of this 

 apparatus to check quantitatively the relationship between the two 

 10-mm. openings and the large opening with its various reductions. 

 For this purpose a small auxiliary chamber (approximately 1 cubic meter 

 in size) was connected with the pipe leading to the air-impeller (a, fig. 8) 

 on the sampling apparatus. Into this chamber a known amount of 

 carbon dioxide was admitted from a steel cyUnder of hquefied carbon 

 dioxide. These cylinders held approximately 2.5 kilograms each. The 

 gas was found to be of an extraordinarily high degree of purity, with 

 practically no appreciable correction for the slight amount of dissolved 

 air. By weighing this cylinder of carbon dioxide on a balance capable 

 of recording 1 centigram, 100 to 400 grams could be admitted as rap- 

 idly or as slowly as desired. Repeated tests with the subsidiary cham- 

 ber showed that the aliquoting device functioned perfectly, regardless 

 of whether the carbon dioxide was rushing into the chamber as rapidly 

 as possible or entering very slowly over a long period. 



By knowing (1) the amount of carbon dioxide admitted to the cham- 

 ber as shown by the difference in weight of the cylinder at the begin- 

 ning and end of the test, (2) the amount of carbon dioxide absorbed in 

 the soda-lime bottle, and (3) the volume of air passing through the gas 

 meter, the ratio could be computed between the 10-mm. openings and 

 the particular opening used for the large discharge from the wind 

 chest. For experimental purposes several disks with orifices of vary- 

 ing size were prepared. These disks were made of brass, were 1.5 mm. 

 thick, and 110 nun. in diameter. They had a rim of sheet brass 40 

 mm. wide, soldered into the edge, thus forming a cup which could be 

 dropped into the annular space filled with water surrounding the large 

 opening of the wind chest. Disks were made with orifices of approx- 

 imately 60, 40, 29, 22, and 16 mm., respectively. The true diameters 

 of these disks, as found from a series of exact caliperings, areas follows: 

 16-mm. disk, diameter 15.92 mm.; 22-mm. disk, diameter 22.03 mm.; 

 29-nQm. disk, diameter 28.75 mm. ; 40-mm. disk, diameter 40.00 mm. ; 

 60-mm. disk, diameter 59.52 mm. A careful calipering of the main 

 discharge opening showed an average internal diameter of 97.00 mm. 

 The true diameter of the 10-mm. openings was 10.11 mm. In all sub- 

 sequent references to these various openings, they are given the number 



