1300 H^EMTK 



under which some glacial acetic acid is now run in. It is then 

 warmed carefully to a temperature just short of that which 

 would cause the acid to boil. If the operation has been suc- 

 cessful, on cooling crystals of htemin will be seen under a micro- 

 scope mixed in either case as in Fig. 231 with a granular debris. 





Fig. 231. H^emin Crystals from a drop of blood. (Kiihne.) 



If they are absent, warm again, adding more acid if necessary. 

 The crystals are dark brown, frequently almost black, elongated 

 rhombic plates and prisms belonging to the triclinic system. 

 In a purified specimen they are arranged singly or in groups as 

 shewn in Fig. 232, and apart from their form are characterized 

 by being strongly doubly-refracting : when examined under the 

 microscope between crossed Nicol prisms those crystals whose 

 axes are suitably inclined to the incident light stand out bright 

 yellow or orange on the dark field. They are quite insoluble 



Fig. 232. ILemin Crystals. (After Preyer.) 



in either water, alcohol, ether, chloroform or dilute acids : they 

 may however be dissolved to some extent in glacial acetic or 

 hydrochloric acids, especially if warmed, and are readily soluble 

 in alkaline carbonates or dilute caustic alkalis, being at the 

 same time decomposed by the latter solvent into luematin and 

 a chloride of the alkali. This fact provides the best means for 

 obtaining pure hsematin. 



A solution of hsematin hydrochloride shews an intense ab- 



