248 THE RED BLOOD CORPUSCLES. [CH. X. 



alcohol in a flask on the water bath and filter. The solution con- 

 tains alkaline haematin free from proteins. It shows the absorption 

 band of alkaline haematin more distinctly than the solution 

 prepared in Ex. 303. 



305. Haemochromogen (reduced alkaline haematin). Pre- 

 pare a solution of alkaline haematin from dilute oxyhaemoglobin 

 as in Ex. 303. Treat 5 cc. with a few drops of ammonium sulphide. 

 The colour of the solution changes to red. Examine with the 

 spectroscope. Two absorption bands are seen in the green. The 

 band nearer the D line (the a band) is very prominent and sharply 

 denned, with its centre at about X 558. The /3 band is much fainter 

 and has its centre at X 520. 



306. To 5 cc. of water add one drop of defibrinated blood and 

 three or four drops of ammonium sulphide. Mix and warm cau- 

 tiously till the oxyhaemoglobin has been completely reduced. Add 

 a few drops of 40 per cent, soda and note the instantaneous forma- 

 tion of haemochromogen. 



NOTE. In very dilute solutions only the a band can be seen. The 

 absorption of light in this region is so intense that if a solution of oxyhaemo- 

 globin, so dilute that its absorption bands cannot be readily seen, be converted 

 by appropriate means into haemochromogen, the a band of this pigment is 

 usually observable. 



307. Acid haematoporphyrin. To a few cc. of concentrated 

 sulphuric acid in a test-tube add two drops of defibrinated blood 

 (see note to Ex. 308) and mix by gentle shaking. Note the rich 

 purple colour of the solution. Examine with the spectroscope. 

 Two bands are seen : the a band, with centre at X 600, being fainter 

 and narrower than the /3 band, centre X 554. 



308. Alkaline haematoporphyrin. To the solution of acid 

 haematoporphyrin just prepared add five or six more drops of 

 defibrinated blood, shaking gently after the addition of each drop. 

 Pour the strong solution into about 50 cc. of cold water in a beaker, 

 stir well and note the precipitate that rises to the surface. Transfer 

 this precipitate to a test-tube by means of a rod ; treat it with a few 

 cc. of alcohol and boil. Add 5 cc. of sodium hydroxide. A solution 

 of alkaline haematoporphyrin is thus obtained, which examined 



