CONDITIONS INFLUENCING DISSOCIATION 327 



The dissociation curve for pure haemoglobin is also foiiiui in 

 Fig. 82, dotted line. It differs from that of whole blood in that its 

 eontour is that of a rectangular hyperbole, wliieh ean be represented 

 approximately by the equation 



[Hb] X [O,] 



K 



[HbO^-J 



(Henderson) 



Influence of the solutes of blood on the dissociation curve. 



From Fig. 82 it may be seen that, at all oxygen tensions, the 



DISSOCIATION CURVE. OF H/EMOGLOBIN AT 37°C. 



too 



lo 20 30 'ND SO 60 ro 80 



TE-NSION OF OXVGEN IN MM OF Mq 



90 



/OO 



Fig. 82. — Dissociation curve representing tlie cciuilibrium between oxygen tension^ 

 oxy-haemoglobin and reduced haemoglobin : 



= Curve from pure 14% haemoglobin .solution. 



= „ „ 14% haemoglobin in plasma. 



— „ „ ,, ,, ,, with increased 



tension of carbon-dio.Nide. 

 Tlie hatched portion represents the amount of haemoglotiin wliieli gives up its oxygen 

 when the oxygen tension is reduced from 100 to 15 nun. Hg. 



percentage saturation of haemoglobin with oxygen is less in blood 

 than in a solution of pure haemoglobin, although the difference is 

 small at tensions above about 80 mm. of Hg. 



The dissociation curves of haemoglobin in solutions of sodium 

 chloride of approximately the same osmotic concentration as 

 plasma (about 0-9 per cent.) (q.v.) are found to lie nearer the 



