Haemoglobin may easily be broken up into two constituents - namely, (a) a colorless substance which is nearly related to the class of proteids called globulin, and (b) a blackish-red amorphous material called hcematin, which contains all the iron of the haemoglobin.

This change is brought about by whatever causes the coagulation of albumin, such as the addition of acids, strong alkalies, and heat above 700 C.