52 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



2. Methaemoglobin. To prepare a solution of methsemo- 

 globin, add to some of the same or a more concentrated solu- 

 tion of blood a few drops of a strong solution of potassium 

 ferricyanide (freshly prepared). The solution turns brown 

 and shows a characteristic spectrum (No. 3 in the Table of 

 Absorption Spectra). Especially to be noted is the strong 

 absorption of light in the blue part of the spectrum. Now 

 add to the methaemoglobin solution a few drops of ammonium 

 sulphide, let stand some minutes, and then shake vigorously 

 with air. The solution now shows the bands of oxy hemo- 

 globin. The methaemoglobin may therefore be converted by 

 reduction and subsequent oxidation into oxy haemoglobin. 



3. Sulphohaemoglobin. Conduct hydrogen sulphide into 

 the blood solution, which has been previously thoroughly 

 shaken with air. It turns brown, then dirty green, due to 

 the formation of Sulphohaemoglobin, and when examined with 

 the spectroscope shows an absorption-band between the yel- 

 low and orange near the C line (E. Harnack). 



VII. Carbon Monozide Haemoglobin. 



Conduct illuminating-gas (or carbon monoxide) into 50 cc. 

 of blood until it becomes distinctly cherry-red. When exam- 

 ined with the spectroscope at the proper dilution it gives 

 almost exactly the same absorption-bands as the oxyhaemo- 

 globin, only they are a little nearer the violet end of the spec- 

 trum. On the addition of ammonium sulphide or Stokes's 

 solution no reduction takes place, however, and the bands 

 remain unchanged. 



To distinguish carbon monoxide haemoglobin from oxy- 

 haemoglobin or to detect the former in the presence of the 

 latter, a great number of reactions have been given, all of 

 which depend upon the greater stability of the carbon mon- 

 oxide haemoglobin (the detection of carbon monoxide haemo- 

 globin in mixtures spectroscopically is difficult and only pos- 

 sible to a certain extent). 



