Of, 1 TO 



RESPIRATION 



HIV 

 263 



TABLE SHOWING THE ABSORPTION COEFFICIENTS FOR BLOOD OF OXYGEN, NITROGEN 



AND CARBON DIOXIDE. 



By the help of the absorption coefficients we can calculate the quan- 

 tities of oxygen, nitrogen, and carbon dioxide which would be dissolved 

 in 100 c.c. of blood shaken with air at room temperature (15 C.) and 

 760 millimetres pressure. From a pressure of 760- millimetres that of 

 the (average) water vapour at 15 C. must be subtracted 12-7 milli- 

 metres giving as total pressure for the air minus water vapour: 

 76012-7=747-3 millimetres. For oxygen, the partial pressure is 



20-99 



of this pressure, 20-92 being the percentage of this gas in the 

 100 . i 



atmosphere measured under dry conditions. 

 20-92 

 100 



x 747-3 - 156-6 millimetres. 



With this partial pressure the amount of oxygen dissolved in 100 c.c. 

 of blood will be 



0-031 x 100 x 156-6 n MQ 



~76Q" = 0-639 c.c., 



where 0-031 is the coefficient of absorption for blood at 15 C. 



But in the lung alveoli the conditions are different. The tempera- 

 ture is 38 C. ; therefore a different coefficient of absorption is required. 

 The air is saturated with vapour, and the amount of water vapour is 

 much increased, giving a partial pressure of 49-3 millimetres; and, 

 lastly, the chemical composition of the air, measured under dry 

 conditions, is different from that of the atmospheric air. Here the 

 composition is, approximately: Oxygen, 14 to 15 per cent.; nitrogen, 

 SO to 80-2 per cent. ; and carbon dioxide 4-8 to 5 per cent. Under 

 these conditions, the amount absorbed by 100 c.c. of blood is 



(Co- 

 efficient) 



0-022 X 



(Partial 

 pressure) 



-A)x(760-49.3) = . 309 _ _ 



Oxygen 



0-01 Ix 80-2 x (760-49-3) 

 Nitrogen .. " 7n =0-825 c.c. 



i OU 



051 x 4-8 x (760 - 49-3 on 

 Carbon dioxide =-^- = 2-29 c.c. 



7t'U 



