DE. A. GrAMG-EE ON THE ACTION OF NITEITES ON BLOOD. 
593 
II. On the Spectrum of Blood acted upon by Nitrites. 
If normal arterialized blood be suitably diluted so as to admit of an accurate examina- 
tion of its absorption-spectrum, and if after the position of the two characteristic absorp- 
tion-bands has been noted, a solution of any nitrite be added to it, it will be noticed 
that when the solution begins to change from a red to a brown tint, the absorption- 
bands undergo notable changes. The two sharply-defined absorption-bands of the 
oxidized colouring-matter become fainter and fainter, and are, indeed, only visible when 
a comparatively thick layer of the fluid is examined. At the same time, if the layer be 
sufficiently thick, it will be noticed that an additional, though comparatively faint, 
absorption-band appears in the red : this band appears absolutely to coincide with that 
of acid hsematin ; it is seen to greatest advantage when so thick a layer of solution is 
examined that all but the red rays are cut; off. The complete change, as seen with the 
spectroscope, is always coincident with the complete change of colour. If, now, the 
solution be made alkaline by the addition of ammonia, the colour changes from the 
chocolate-brown to blood-red again ; simultaneously the absorption-band in the red dis- 
appears, and the two absorption-bands between D and E become more distinct again. 
In addition, however, it is noticed that the portion of the spectrum occupying the 
confines of the yellow and orange has become shaded by a less well-defined absorption- 
band. 
A. B C I) E G- 
I. indicates approximately the position of Fraunhofer’s lines A, B, C, D, E. and G 
in relation to the millimetre scale of the spectroscope used in this research. 
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