CALCULATION OF RESULTS. 69 



frequently of great assistance in indicating such leakage. Furthermore, 

 the residual analysis is used to measure the amount of leak. This point, 

 as well as the general significance of leaks of either oxygen or nitrogen, 

 will be taken up more in detail beyond. 



FACTORS USED IN THE CALCULATION OF THE RESIDUAL ANALYSES. 



The chief factors necessary in the calculations of the residual amounts 

 of carbon dioxide, water vapor, oxygen, and nitrogen in the ventilating 

 air current are the volumes of the gases in the various parts of the sys- 

 tem, the composition of the different portions of air, the volume of the 

 sample taken for analysis, the weights of carbon dioxide and water in 

 the sample drawn through the meter, and the volume percentage of 

 oxygen and nitrogen found by the gasoinetric analysis. 



VOLUMES OF AIR IN AIR-CIRCUIT. 



The volume of the residual air in the different parts of the chamber, 

 pipes, absorbing apparatus, and pans is calculated with considerable 

 accuracy from measurements of dimension, especially for those parts of 

 the system in which the air volumes are not liable to fluctuate. 



VOLUME IN CHAMBER. 



The respiration chamber is 19.27 decimeters high, 12.17 decimeters 

 wide, and 21.38 decimeters long. The corners of the floor and ceiling 

 are rounded, the radius of curvature being 1.27 decimeters. From 

 these data the volume of the chamber proper is computed to be 4,987.0 

 liters. A recess in the wall provides for the window, and as this does 

 not set flush with the inner wall, its volume must be added to that of 

 the rest of the chamber. The recess is 7.24 decimeters high, 5.20 deci- 

 meters wide, and 0.57 decimeter deep. Its volume consequently equals 

 21.4 liters, which, added to the volume of the chamber, 4,987.0 liters, 

 equals 5,008.4 liters. 



A certain amount of material in the apparatus can be considered 

 permanent fixtures, such a? the absorbing system, the air-pipe and 

 metal work (other than the metal of the walls) , the telephone and bat- 

 teries, and various smaller pieces of apparatus that are in regular use. 

 The volume occupied by these permanent fixtures is determined by 

 measurement of their dimensions or by calculating the volume by 

 means of the specific gravity when the weight is known. The volumes 

 thus obtained are as follows, in liters: Heat-absorbing system, 5.94; air- 

 pipes and metal work, i.o; switch, 0.3 ; telephone and battery, 2.0 ; 

 making a total of 9.24 liters to be deducted from the apparent volume, 

 5,008.4 liters, in all calculations. 



