222 Journal of Agricultural Research voi. m. No. 3 



of the D line and corresponding to the spectrum of NO-hemochromogen, 

 as described by Haldane, except that the second band at the left of the 

 E line was not visible. The addition of Stokes's solution caused no change 

 in the color or spectrum of the solution. On standing overnight the red 

 color of the solution had changed to brown and the spectrum had changed 

 to that of alkaUne hematin. 



A dilute alcoholic, ammoniacal solution of hematin was treated with a 

 small quantity of a concentrated solution of hydrazin sulphate. The 

 brown color of the hematin solution quickly changed to the bright pink 

 of hemochromogen, with a corresponding change in spectrum. The hemo- 

 chromogen solution was then saturated with hydrogen, nitric oxid, and 

 hydrogen in turn. On saturation with nitric oxid the pink color of the 

 solution quickly changed to cherry red, and spectroscopic examination 

 showed a heavy dark band just at the right of the D line. No other 

 bands were observed, even though the solution was examined in a deep 

 absorption cell. 



The two substances produced, either by saturation of a solution of 

 hematin with nitric oxid or by similar treatment of a solution of hemo- 

 chromogen, are apparently identical. The evidence seems to show that 

 this substance is the compound NO-hemochromogen. 



The structural relation between NO-hemoglobin and NO-hemochro- 

 mogen is simple. NO-hemoglobin is a molecular combination of nitric 

 oxid and hemoglobin — the latter compound consisting of the proteid 

 group, globin, on one hand, and the coloring group, hemochromogen, on 

 the other. NO-hemoglobin and NO-hemochromogen differ from each 

 other simply in that one contains the proteid group, globin, while the 

 other does not. Apparently, then, a method of treatment which would 

 split off the globin group from NO-hemoglobin should result in the pro- 

 duction of NO-hemochromogen, provided, of course, that the procedure 

 did not in turn change or destroy the NO-hemochromogen produced. 



As has already been noted by Haldane, it was found that when a solu- 

 tion of NO-hemoglobin was heated to boiling a brick-red precipitate 

 formed, in contrast to the dark-brown precipitate which formed on heat- 

 ing a solution of oxyhemoglobin or of blood. The brick-red precipitate 

 was filtered off and was then extracted with alcohol, which gave a light- 

 red colored extract showing a spectrum with a fairly heavy band just at 

 the right of the D line. This spectrum corresponds with that of 

 NO-hemochromogen. On standing, the color of the extract faded 

 rapidly. 



A solution of oxyhemoglobin was treated with one-hundredth normal 

 nitrous acid and showed a spectrum corresponding to that of NO-hemo- 

 globin. The color of the solution changed from the bright red of oxy- 

 hemoglobin to the dark cherry-red characteristic of NO-hemoglobin. 

 Treatment with sodium nitrite did not affect the color or spectrum of the 



