

BLOOD. 2O5 



3. Carbon Monoxide Haemoglobin. The preparation of this 

 pigment may be easily accomplished by passing ordinary illumi- 

 nating gas 1 through defibrinated ox-blood. Blood thus treated 

 assumes a brighter tint (carmine) than that imparted by oxy- 

 haemoglobin. In very dilute solution oxyhaemoglobin appears yel- 

 lowish-red whereas carbon monoxide haemoglobin under the same 

 conditions appears bluish-red. Examine the carbon monoxide 

 haemoglobin solution spectroscopically. Observe that the spectrum 

 of 'this body resembles the spectrum of oxyhsemoglobin in showing 

 two absorption-bands between D and E. The bands of carbon mon- 

 oxide haemoglobin, however, are somewhat nearer the violet end of 

 the spectrum. Add some Stokes' reagent to the solution and again 

 examine spectroscopically. Note that the position and intensity of 

 the absorption bands remain unaltered. 



The following is a delicate chemical test for the detection of 

 carbon monoxide haemoglobin : 



Tannin Test. Divide the blood to be tested into two portions 

 and dilute each with four volumes of distilled water. Place the 

 diluted blood mixtures in two small flasks or large test-tubes and 

 add 20 drops of a 10 per cent solution of potassium ferricyanide. 2 

 Allow both solutions to stand for a few minutes, then stopper the 

 vessels and shake one vigorously for 10-15 minutes, occasionally re- 

 moving the stopper to permit air to enter the vessel. 3 Add 5-10 

 drops of ammonium sulphide (yellow) and 10 c.c. of a 10 per- 

 cent solution of tannin to each flask. The contents of the shaken 

 flask will soon exhibit the formation of a dirty olive-green precipi- 

 tate, whereas the flask which was not shaken and which, therefore, 

 still contains carbon monoxide haemoglobin, will exhibit a bright 

 red precipitate, characteristic of carbon monoxide haemoglobin. 

 This test is more delicate than the spectroscopic test and serves to 

 detect the presence of as low 7 a content as 5 per cent of carbon 

 monoxide haemoglobin. 



4. Neutral Methaemoglobin. Dilute a little defibrinated blood 

 (i : 10) and add a few drops of a freshly prepared 10 per cent 

 solution of potassium ferricyanide. Shake this mixture and ob- 

 serve that the bright red color of the blood is displaced by a brown- 

 ish red. Now dilute a little of this solution and examine it spec- 

 troscopically. Note the single, very dark absorption-band lying 



1 The so-called water gas with which ordinary illuminating gas in diluted con- 

 tains usually as much as 20 per cent of carbon monoxide (CO). 



2 This transforms the oxyhsemoglobin into methaemoglobin. 



3 This is done to free the blood from carbon monoxide haemoglobin. 



