GENERAL DESCRIPTION OF RESPIRATION APPARATUS. 



TENSION 

 EQUALIZER 



brass rod is drawn into this opening, thus producing an air-tight closure. 

 When in actual use during the process of weighing, a thin rubber diaphragm 

 prevents leakage of air through this opening. The escape of heat through 

 the weighing-tube is minimized by having this tube of hard rubber. 



VENTILATING AIR-CURRENT. 



The ventilating air-current is so adjusted that the air which leaves the 

 chamber is caused to pass through purifiers, where the water-vapor and 

 the carbon dioxide are removed, and then, after being replenished with fresh 

 oxygen, it is returned to the 

 chamber ready for use. The 

 general scheme of the respi- 

 ration apparatus is shown in 

 fig. 27. The air leaving the 

 chamber contains carbon di- 

 oxide and water-vapor and 

 the original amount of nitro- 

 gen and is somewhat deficient 

 in oxygen. In order to pur- 

 ify the air it must be passed 

 through absorbents for car- 

 bonic acid and water-vapor 

 and hence some pressure is 

 necessary to force the gas 

 through these purifying ves- 

 sels. This pressure is ob- 

 tained by a small positive 

 rotary blower, which has been 

 described previously in de- 

 tail.* The air is thus forced 

 successively through sulphu- 

 ric acid, soda or potash lime, 

 and again sulphuric acid. Finally it is directed back to the respiration 

 chamber free from carbon dioxide and water and deficient in oxygen. Pure 

 oxygen is admitted to the chamber to make up the deficiency, and the air 

 thus regenerated is breathed again by the subject. 



H 2 O 

 ABSORBED 



CO, 

 ABSORBED 



H 2 O 

 ABSORBED 



FIG. 27. Diagram of ventilation of respiration calorimeter. 

 The air is taken out at lower right-hand corner and 

 forced by the blower through the apparatus for absorb- 

 ing water and carbon dioxide. It returns to the calo- 

 rimeter at the top. Oxygen can be introduced into the 

 chamber itself as need is shown by the tension equalizer. 



BLOWER. 



The rotary blower used in these experiments for maintaining the venti- 

 lating current of air has given the greatest satisfaction. It is a so-called 



* W. O. Atwater and F. G. Benedict: A respiration calorimeter with appliances 

 for the direct determination of oxygen. Carnegie Institution of Washington 

 Publication No. 42, p. 18. (1905.) 

 5 



