THE BLOOD. 79 



chanically by the crystals. The formula of the hsemin crystals prepared by 

 means of amyl alcohol is, according to NENCKI and SIEBER, 



Haemin crystals form in large masses a bluish-black powder, but 

 are so small individually that they can only be seen by the micro- 

 scope, They consist of dark-brown or nearly brownish-black, long, 

 rhombic, or spool-like crystals, isolated, or grouped as crosses, 

 rosettes, or starry forms. They are insoluble in water, dilute acids 

 at the normal temperature, alcohol, ether, and chloroform. They 

 are slightly dissolved by glacial acetic acid and warmth. They 

 dissolve in acidified alcohol, as also in dilute caustic or carbonated 

 alkalies; and in the last case they form, besides alkali chlorides, 

 soluble haematin alkali, from which the haematin may be precipi- 

 tated by an acid. 



The preparation of haemin crystals is always the starting-point 

 for the preparation of haematin. According to HOPPE-SEYLER, 

 shake the blood-corpuscles which have been washed with common- 

 salt solution (see page 66) with water and ether, then filter the solu- 

 tion of blood-coloring matters, concentrate strongly, mix with 10-20 

 vols. glacial acetic acid, and heat for 1-2 hours on the water-bath. 

 After diluting with several volumes of water, allow the liquid to 

 stand a few days. The crystals which separate are then washed 

 with water, boiled with acetic acid, and then washed again with 

 water, alcohol, and ether. NENCKI and SIEBEK coagulate the 

 sediment of the blood-corpuscles by alkali, allow the coagulum to 

 dry incompletely in the air, rub it fine, and then boil it with amyl 

 alcohol after the addition of a little hydrochloric acid. The crys- 

 tals which separate from the filtrate after cooling are washed with 

 water, alcohol, and ether. If haemin crystals be dissolved in dilute 

 caustic alkali, haematin may be precipitated from the solution by 

 the addition of acid; and from this haematin pure haemin crystals 

 may be prepared by heating with glacial acetic acid and a little 

 common salt. 



In preparing haemin crystals in small amounts proceed in the 

 following manner : The blood is dried after the addition of a small 

 quantity of common salt, or the dried blood may be rubbed with a 

 trace of common salt. The dry powder is placed on a microscope- 

 slide, moistened with glacial acetic acid, and then covered with the 

 cover-glass. Add, by means of a glass rod, more glacial acetic acid 

 by applying the drop at the edge of the cover-glass, until the space 

 between the slide and the cover-glass is full. Now warm over a very 

 small flame, with the precaution that the acetic acid does not boil 



