266 PHYSIOLOGICAL CHEMISTRY 



of inorganic chlorides are not formed. In Teichmann's method crystals 

 of sodium chloride often obscure the hemin crystals. 



(c) Atkinson and Kendall's Method. Introduce a small amount of the solution 

 under examination into a tube closed at one end, add sodium chloride and glacial 

 acetic acid as in Teichmann's method, 1 fuse or tightly plug the open end of the tube 

 and heat for fifteen minutes in a boiling water-bath. 2 Remove the tube and permit 

 it to cool to room temperature spontaneously. When the tube has cooled, break 

 it open, transfer the contents to a watch glass or small evaporating dish and con- 

 centrate on a water-bath until the volume of the fluid in the watch glass or dish 

 has been reduced to a few drops. Transfer a drop of this fluid to a slide, cover 

 with a cover slip, allow the slide to stand for a few minutes and examine it under a 

 microscope. Compare the crystals with those shown in Figs. 78 and 79, page 265. 

 In case crystals of sodium chloride (see Fig. 80) obstruct the view of the hemin 

 crystals, dissolve the sodium chloride crystals by running a drop of water under 

 the cover slip. 



(d) v. Zeynek and Nencki's Method. To 10 c.c. of defibrinated blood add acetone 

 until no more precipitate forms. Filter off the precipitated protein and extract it 

 with 10 c.c. of acetone made acid with 2-3 drops of hydrochloric acid. Place a 

 drop of the resulting colored extract on a slide, immediately place a cover-glass in 

 position and examine under the microscope. Upon the evaporation of the acetone, 

 crystals of hemin will form. Larger crystals may be obtained by evaporating the 

 acetone extract about one-half, transferring it to a stoppered vessel and allowing it 

 to remain overnight. 



(e) Schalfijew's Method. Place 20 c.c. of glacial acetic acid in a small beaker 

 and heat to 8oC. Add 5 c.c. of strained defibrinated blood, again bring the 

 temperature to 8oC., remove the flame and allow the mixture to cool. Examine 

 the crystals under the microscope and compare them with those reproduced in 

 Figs. 78 and 79, page 265. 



1 6. Catalytic Action. To about 10 drops of blood in a test-tube add twice the 

 volume of hydrogen peroxide, without shaking. The mixture foams. What is 

 the cause of this phenomenon? 



17. Crystallization of Oxyhemoglobin. Reichert's Method. Add to 5 c.c. 

 of the blood of the dog, horse, guinea-pig, or rat, before or after laking, or de- 

 fibrinating, from i to 5 per cent of ammonium oxalate in substance. Place a 

 drop of this oxalated blood on a slide and examine under the microscope. The 

 crystals of oxyhemoglobin will be seen to form at once near the margin of the 

 drop, and hi a few minutes the entire drop may be a solid mass of crystals. 

 Compare the crystals with those shown in Figs. 70 to 76, pages 251 to 254. 



18. Preparation of Hematin. Place 100 c.c. of hemolyzed (laked) blood in a 

 beaker and add 95 per cent alcohol until precipitation ceases. What bodies are 

 precipitated? Transfer the precipitate to a flask and boil with 95 per cent alcohol 

 previously acidulated with sulphuric acid. Through the action of the acid the 

 hemoglobin is split into hematin and a protein body called globin. Later the 

 "sulphuric acid ester of hematin'' is formed, which is soluble in the alcohol. Con- 

 tinue heating until the precipitate is no longer colored, then filter. Partly saturate 

 the filtrate with sodium chloride and warm. In this process the "hydrochloric acid 



1 Care should be taken not to add too great an excess of these reagents. 



2 This process insures constancy of temperature and strength of reagents. 



