116 , THE BLOOD. 



then enough ammonia to make it faintly alkaline,, and add 

 1 drop to the blood solution. The oxyhaemoglobin gives 

 up its oxygen to the iron compound, becoming changed in 

 a short time to haemoglobin, as is shown by the dark color. 

 An excess of the reducing solution should be avoided. 



244. Shake the dark solution of hemoglobin with 

 air and notice the change in color to a scarlet, showing the 

 formation of oxyhsemoglobin. 



245. Examine a very dilute solution of blood with 

 the spectroscope in the following manner: First examine 

 the solar spectrum by looking through the spectroscope 

 with its slit directed toward a window. Close the slit to 

 a very narrow opening, and focus by sliding the focusing 

 tube until the fine, dark lines are seen clearly. There are 

 hundreds of these so-called Fraunhofer lines in the spec- 

 trum of the sun, but with an ordinary instrument many 

 are indistinct. A few of the most prominent should be 

 noticed and s used to locate the position of the dark bands 

 in the spectra of haemoglobin and its derivatives. The 

 most noticeable are the C line in the red, the D line in 

 the yellow, the E and & not far apart in the green and F 

 in the blue. If there are fine, black lines running length- 

 wise of the spectrum they are caused by dust in the slit. 

 Next make solutions of blood and water of different dilu- 

 tions and examine the spectrum which is given when a 

 test-tubeful of the solution is held before the slit after the 

 solution has been shaken with air to form oxyhaamoglobin. 

 Notice the position of the two bands and observe that this 

 does not change with the different dilutions, although the 

 bands may be wider or more distinct when the solution is 

 concentrated. 



246. To the solutions of oxyhsemoglobin add a few 

 drops of ammonium sulphid, and after they have stood a 



