Haematin is a secondary product, being the result of oxidation of a substance called hcemochromogen, which is the first outcome of the decomposition of the haemoglobin by acids or strong alkalies. Haemochromogen or reduced hcematin, as it may be called, can be obtained from haematin by acting on that body with ammonium sulphide, but it can only be preserved in.an atmosphere of hydrogen or nitrogen, as it immediately takes up oxygen to form hsematin on exposure to the air. The formula C68H70N8Fe2O10 has been given for haematin. It dissolves in weak alkaline and acid solutions, but not in water or in alcohol.
Haematin is readily prepared by mixing acetic acid with a strong solution of haemoglobin, which becomes a dark-brown color. The dark haematin can be removed by ether. But if the acid used be strong, the solution of haematin is found to be free from iron. This iron-free haematin is called haematoporphyrin or hcematoin. If now the acid haematin solution be saturated with ammonia, the iron again becomes united with the haema-toin, forming alkali-haematin.