EXAMINATION OF BLOOD. 57 



XII. Coagulation of the Blood by Heating. 



Diluted blood heated to boiling and filtered. 



Colorless filtrate, tested for Coagulum, colored brown from 



sugar and salts. hsematin. 



In every investigation of the soluble constituents of the 

 blood it is necessary first to precipitate the proteids. This is 

 accomplished either by pouring the blood into four times its 

 volume of absolute alcohol or by heating to boiling. 



Heat a mixture of 30 to 50 cc. of blood and six to eight 

 times its volume of water over a free flame, and with constant 

 stirring, to vigorous boiling, taking care to keep the reaction 

 neutral or very faintly acid by the cautious addition of dilute 

 acetic or sulphuric acids, then filter. The filtrate should be 

 lear and colorless, which is only possible with fresh blood. 

 The solution is evaporated to a small volume, then divided 

 into halves, one of which is used to perform Trommer's test 

 with some freshly mixed Fehling's solution, the other is 

 further evaporated on the water-bath, a drop allowed to 

 evaporate on a microscope-slide and* examined under the 

 microscope: crystals of sodium chloride. Evaporate the 

 residue to dryness and incinerate : salts, especially sodium 

 chloride. Test for chlorides with silver nitrate, for phos- 

 phates with ammonium molybdate. The test for sugar fre- 

 quently does not succeed with commercial blood. 



The brown-colored coagulum obtained is washed, well 

 pressed, ground in a mortar with 100 cc. of absolute alcohol, 

 ,3 to 5 cc. of concentrated sulphuric acid gradually added, 

 ground again, then the mixture is placed in a flask and heated 

 on the water-bath. A brown-colored solution results and an 

 almost colorless residue of coagulated albumin. Filter, and 

 examine the filtrate spectroscopically (No. 4 in the Table of 

 Absorption Spectra). Especially characteristic is the band 



