280 PHYSIOLOGICAL CHEMISTRY 



of a protein combined with hemochromogeii or some similar 

 substance. In connection with the study of hemoglobin, some 

 other constituents of blood will be considered. Recall the inor- 

 ganic materials present in blood as determined in an earlier 

 chapter. What proteins have been observed in the blood earlier 

 in this chapter ? In blood are also found fat, sugar, extractives, 

 protein decomposition products and various other substances. 

 The methods for quantitative estimation of these substances will 

 be found in Chap. VI. 



Spectroscopic behavior of hemoglobin. Study the spectro- 

 scopic behavior of hemoglobin and its derivatives as follows, two 

 students working together. 



35. Oxygenation of Hemoglobin. The color of oxyhemoglobin 

 is a much lighter and more brilliant red than that of hemoglobin. 

 Dilute defibrinated blood with 5 volumes of water. The blood 

 is ' ' laked, ' ' that is, the hemoglobin leaves the corpuscles and goes 

 into solution in the water. The liquid, which was opaque, be- 

 comes clear. Laking may be brought about in various other 

 ways, as by the addition of a small amount of ether, toluol, etc. 

 Shake up the laked blood with air, closing the tube with the 

 thumb. The color becomes bright red, as the hemoglobin is 

 changed into the brighter colored oxyhemoglobin. 



Prepare three test tubes of this diluted blood. To two of 

 them add Stokes' fluid. (This is a mild reducing agent, which 

 contains 2% Fe S0 4 , 3% tartaric acid, and ammonia in amount 

 sufficient to redissolve the precipitate which forms on first adding 

 this reagent. The reagent must be freshly prepared. ) The color 

 becomes darker red. The oxyhemoglobin has been reduced to 

 hemoglobin. Pour the blood in one of the Stokes' reagent tubes 

 several times from one test tube to another. The brighter oxy- 

 hemoglobin color reappears. Evidently hemoglobin and oxy- 

 hemoglobin are readily converted one into the other. Consider 

 this property in connection with the role which hemoglobin plays 

 in the organism. 



36. Spectroscopic Study of Blood Pigment. By means of a 

 spectroscope observe the spectrum produced by a luminous gas 



