EXAMINATION OF BLOOD. 51 



Examine under the microscope. To purify the oxy haemo- 

 globin, filter at a low temperature, press out the mother- 

 liquor, dissolve the crystals in as small a quantity of water 

 as possible at 30, filter quickly, add one-fifth to one-fourth 

 the volume of alcohol gradually and with constant stirring 

 to prevent coagulation, and let stand at until crystalliza- 

 tion is complete. 



VI. Spectroscopic Examination. 1 



1. Oxyhaemoglobin and Haemoglobin. Ten cubic centi- 

 meters of blood are diluted to 100 cc., filtered, then gradually 

 further diluted until the solution when examined spectro- 

 scopically shows distinctly the oxyhsemoglobin bands between 

 D and E in the yellow and green of the spectrum (see Table 

 of Absorption Spectra, 2 No. 1). Then add to the solution a 

 few drops of the so-called Stokes's solution (solution of fer- 

 rous ammonium tartrate, which must always be freshly 

 prepared, made by dissolving in water a piece of ferrous sul- 

 phate as big as a pea, adding as much tartaric acid as. may 

 be held on the point of a knife-blade and then ammonia 

 to alkaline reaction: clear greenish solution). The blood 

 changes its color at once, becomes bluish or violet, and shows 

 in place of the two absorption-bands a broad band due to 

 haemoglobin (No. 2 in the Table of Absorption Spectra). The 

 reduction may also be brought about by adding a few drops 

 of ammonium sulphide solution and allowing the mixture 

 to stand for some minutes; but this takes longer and in 

 addition to the broad band of the haemoglobin there always 

 appears a weaker and narrower band in the red, which pre- 

 sumably comes from the sulphohaemoglobin compound. 



1 For most work in physiological chemistry the Browning pocket spec- 

 troscope is to be preferred on account of its convenience. O. 



2 For a more recent table of absorption spectra, see Ziemke and Miiller, 

 Archiv fur Anat. u. Physiol., 1901, Sp. Bd. 177. O. 



