658 



PHYSIOLOGICAL CHEMISTRY. 



a. Oxyh&moglobin. Dilute 10 c.c. of blood with 90 c.c. of water, and filter. 

 Place part of the solution in a glass vessel with parallel sides and examine 

 with a spectroscope. When the solution is so concentrated the spectrum 

 will probably be entirely shut off as far as the yellow or orange, but on gradu- 

 ally diluting with water a spectrum is finally seen which shows two absorption - 

 bands to the right of the D line. The right-hand band is broader, fainter, and 

 less sharply denned than the other, and the color of the light which emerges 

 from the left limb of the left hand is yellow. When the solution is further 

 diluted the bands disappear simultaneously. (Fig. 72, a.} 



b. Reduced haemoglobin. When a solution of oxy haemoglobin is treated with 

 a reducing agent the coloring-matter loses oxygen and is changed to hsemo- 



FIQ. 72. 



Yellow 



Qreen 



Cyan-blue 



Absorption-spectra of blood constituents, a, oxyhaemoglobin. 

 6, reduced haemoglobin, c, methsemoglobin. d, haematine. e, 

 reduced hsematine. /, hsematoporphyrin. g, carbon monoxide 

 haemoglobin. 



globin. Stokes' fluid is the most suitable reagent for reducing, and is prepared 

 as follows: Dissolve 3 grammes of selected crystals of ferrous sulphate in cold 

 water and add a cold aqueous solution of 2 grammes of tartaric or citric acid. 

 Make up with water to a volume of 100 c.c., and immediately before using add 

 ammonia-water until the precipitate which forms at first is redissolved. 



Prepare a solution of oxyhsemoglobin which will show the characteristic ab- 

 sorption-bands. Allow a few drops of Stokes' fluid to flow into the solution, when 

 its color changes to a purple or violet, and the spectrum shows a single broad 



