OPTICAL PROPERTIES OF BLOOD. 239 



it would be well to employ several dilutions, beginning with No. II of the 

 series given above. 



Spectrum of Carbon Monoxide Hemoglobin. It has 



been already mentioned that the spectrum of carbon monoxide 

 hemoglobin is very similar to that of oxyhemoglobin. This 

 may be found by a simple test. 



Ex. Into diluted blood, as before, pass a stream of common illuminat- 

 ing gas until the liquid is saturated, which requires but a few minutes. 

 On placing the tube in front of the spectroscope the two dark bands de- 

 scribed will be seen, and slightly farther from the yellow than is the case 

 with oxyhemoglobin. 



These bands do not change in extent or position by agitation of the 

 liquid with air, as follows with reduced hemoglobin, and when the liquid 

 is treated with ammonium sulphide or with Stokes' reagent no reduction 

 takes place. The two bands persist 



Spectrum of Methemoglobin. This is characterized by a band in the 

 yellowish red and by a broad band in the blue. To some moderately 

 dilute blood add a few drops of fresh solution of potassium ferricyanide. 

 The mixture becomes brown. It has been already explained that by care- 

 ful reduction with a small amount of ammonium sulphide hemoglobin is 

 regenerated. This may be followed by the spectroscope. Add a few 

 drops of the sulphide solution, allow the mixture to stand a short time 

 and then shake vigorously in the air. Oxyhemoglobin bands now appear. 



The Hematin Spectra. Of these the spectrum of the pigment in weak 

 acid mixture is the most characteristic. This may be obtained by first 

 coagulating 10 cc. of blood and 50 cc. of water by vigorous boiling, enough 

 weak sulphuric acid being added to maintain an acid reaction. The coag- 

 ulum is separated, pressed dry and rubbed up in a mortar with 25 cc. of 

 absolute alcohol and I cc. of strong sulphuric acid gradually added. The 

 mixture is then transferred to a flask and heated half an hour on the 

 water-bath. After cooling the filtered liquid may be examined. A strong 

 dark band in the red is plainly seen. 



Different spectra are found after alkaline treatment. Warm some di- 

 luted blood with a few drops of sodium hydroxide solution until a brown- 

 ish-green color results. The absorption spectrum of this liquid is not 

 characteristic. The whole of the field from red to violet is dark. On 

 careful reduction with a little ammonium sulphide or Stokes' solution the 

 spectrum of hemochromogen or reduced hematin may be obtained. This 

 consists of two sharp bands between D and E, somewhat like those of 

 oxyhemoglobin, but nearer E. 



QUANTITATIVE SPECTRUM ANALYSIS. 



The amount of hemoglobin in a solution may be very accurately esti- 

 mated by the aid of the spectroscope, but an instrument with special 



