DERIVATIVES OF HEMOGLOBIN. 41 



it is dichroic. Observe the spectrum of alkali-hsematin in 

 the filtrate (Fig. 5, 6). 



(d.) Evaporate the filtrate from (c.) to dryness on a water- 

 bath. Extract the residue with boiling water. The black 

 residue is washed on a filter with distilled water, alcohol, 

 and ether, and dried in a hot chamber at 120 C. This 

 is nearly pure hsematin. 



(e.) It is convenient to keep in stock hsematin prepared 

 as follows : Extract defibrinated blood or blood-clot (ox 

 or sheep) with rectified spirit containing pure sulphuric 

 acid (1 : 20). Filter, the solution gives the spectrum of 

 acid-hsematin. Add an equal volume of water and then 

 chloroform. The chloroform becomes brown, and there is a 

 precipitate of proteids. Separate the chloroform extract, 

 wash it with water to remove the acid. Separate the chloro- 

 form, and allow it to evaporate. The dark brown residue is 

 impure hsematin. When dissolved in alcohol and caustic 

 soda it gives the spectrum of alkali-hrematin, and on 

 adding ammonium sulphide that of hsemochromogen. If it 

 is dissolved in H 2 SO 4 , and filtered through asbestos, the red 

 filtrate gives the spectrum of hsematoporphyrin (MacMunn). 



5. Hsemin Crystals. Place some powdered dried blood on a glass 

 slide, add a crystal of sodium chloride, 

 and a few drops of glacial acetic acid. x 



Cover with a cover-glass, and heat care- ** ^~ \ ^ 



fully over a flame until bubbles of gas ^ % v v 



are given off. After cooling, brown 

 or black rhombic crystals of hsematin x 

 are to be seen with a microscope " >N 



6. Detection of Blood Stains. Use a * ^ y 



piece of rag stained with blood. ^ \ v . v **~ 



(a.) Moisten a part of the stain I ^ ^ \ x. 



with glycerin, and after a time Fig. 7. Harniin Crystals 



express the liquor, and observe it prepared from traces 



microscopically for blood-corpuscles. * blood. 



(b.) Tie a small piece of the stained cloth to a thread, 

 place the cloth in a test-tube with a few drops of distilled 

 water, and leave it until the colouring-matter is extracted. 



