352 VEHICLES OF CHEMICAL CORRELATION 



Stokes' reagent is added to it. This is due to the presence of Carbon 

 Monoxide Hemoglobin, which may also be obtained by blowing a 

 stream of carbon monoxide or of illuminating gas through a solution 

 of oxyhemoglobin or reduced hemoglobin. In the former case the 

 oxygen combined with the hemoglobin is quantitatively displaced by 

 the carbon monoxide, a given volume of carbon monoxide displacing 

 an equal volume of oxygen. We can readily distinguish between 

 normal arterial blood and the blood obtained after carbon monoxide 

 poisoning, in the first place by the lack of effect of Stokes' reagent 

 upon the color of the carbon monoxide hemoglobin, and in the second 

 place by the effect of adding concentrated sodium hydroxide (specific 

 gravity 1.3) in the proportion of two volumes of sodium hydroxide 

 solution to one volume of blood. Blood containing carbon-monoxide 

 hemoglobin yields a cinnabar-red precipitate, whereas normal blood 

 yields a dingy brown precipitate. Furthermore, Tannic Acid yields 

 with normal blood a brownish-green precipitate, and with carbon- 

 monoxide blood a pale crimson-red precipitate. The spectrum shows 

 two absorption-bands similar to those of oxyhemoglobin but nearer 

 to the violet end of the spectrum. The carbon monoxide may be 

 dissociated from the hemoglobin by the prolonged action of a vacuum 

 or of a stream of oxygen or an indifferent gas. 



The quantity of oxygen or carbon monoxide which combines with 

 one gram of hemoglobin is 1.34 c.c. at C. and 760 m.m. Hg. 

 This corresponds to one molecule of oxygen or carbon monoxide for 

 every atom of iron in the hemoglobin molecule. If, therefore, we 

 regard the molecule of hemoglobin as containing one atom of iron, 

 the reaction between hemoglobin and oxygen appears as a simple 

 bimolecular reaction as follows: 



Hb + O 2 ^ HbO 2 



The reaction proceeding from left to right when the partial pressure 

 of oxygen is increased, as it is in the lungs, and from right to left when 

 the partial pressure of oxygen is reduced, as it is in the tissues. Sim- 

 ilarly the interaction with carbon monoxide may be represented as 

 follows: 



Hb + CO ^1 HbCO 



Designating the concentration of reduced hemoglobin in any solu- 

 tion by the symbol Cr, that of oxyhemoglobin by the symbol Co, and 

 that of oxygen by the symbol "b," then applying the mass-law to the 

 balanced reaction: 



Hb + O 2 ^ HbO 2 



Cr b Co 



We would have, at equilibrium: 



Cr X b = KCo 



