PROTEINS 283 



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. 



40. Methemoglobin. 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. 



41. 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 

 into two, a broad dark band in the green between b and F, and a 

 narrow fainter band to the left of E. A fourth band may appear 

 on the violet side of D. 



42. Acid Hematoporpkyrin. To 5 c.c. of concentrated sul- 

 phuric acid in a test tube add 2-3 drops of undiluted defibrinated 

 blood, mixing well after the addition of each drop. Observe the 

 color and chart the spectrum. If the color is too dark, dilute 

 with glacial acetic acid. 



Crystallization of Blood Pigment. 



43. Hemoglobin Crystals. Place a drop of defibrinated rat 

 or guinea pig blood on a slide, add an equal volume of water, 



