246 PHYSIOLOGICAL CHEMISTRY 



gent and observe the spectrum. Record. Repeat with blood 

 diluted 80 and 160 times. 



(e) Carbon Monoxide Hemoglobin. Prepare a solution of 

 carbon monoxide hemoglobin by diluting blood 160 times, and, in 

 the hood, passing illuminating gas through the liquid. Observe 

 the cherry red color. Observe the solution spectroscopically and 

 chart it, comparing the location of the bands carefully with those 

 given by an oxyhemoglobin solution. To a little of the carbon 

 monoxide hemoglobin solution add Stokes ' reagent. Observe that 

 the spectrum does not change, as did that of oxyhemoglobin, 

 which it resembles, under similar conditions. 



Although carbon monoxide forms a fairly stable compound 

 with hemoglobin, still it is possible to remove the carbon mon- 

 oxide by passing a brisk air stream through the solution for some 

 time. The solution will contain oxyhemoglobin, as can be dem- 

 onstrated by reducing with Stokes ' reagent. The oxyhemoglobin 

 is reduced to hemoglobin. 



(f) MetJiemoglobin. To a small volume of blood diluted ten 

 times add a few drops of a fresh solution of potassium ferricya- 

 nide. Methemoglobin is formed. The color becomes a dirty 

 brown. Examine the solution with the spectroscope, diluting 

 somewhat if it is too opaque, and chart. While one student is 

 observing the spectrum, let his partner add Stokes' fluid to the 

 liquid in the cell. Observe that the methemoglobin spectrum 

 gives way to that of oxyhemoglobin, which in turn is replaced by 

 that of hemoglobin. The reducing agent first changes methemo- 

 globin back into oxyhemoglobin (these two compounds contain 

 the same amount of oxygen) from which the oxygen is then re- 

 moved by the reducing agent, hemoglobin being produced. 



(g) Acid hematin may be prepared by treating defibrinated 

 blood with half its volume of glacial acetic acid and an equal 

 volume of ether. The liberated hematin dissolves in the ether, 

 and this solution may be used for a spectroscopic examination. 

 It shows a distinct band between C and D, somewhat nearer C 

 than the band in the methemoglobin spectrum. A second fainter 

 band appears between D and F. On dilution this band divides 



