Putrefaction of blood for 6-8 mo. in the presence of Na2CO3 produced a new hemin, deuterohemin, with spectral bands at 545.6 and 516.2. On reduction deuteroporphyrin was obtained. Various derivatives of these substances were prepared. It is probable that the new hemin is formed by the removal of 2 unsaturated side chains from hemin during the putrefaction, a type of biological reaction not described before. Deuteroporphyrin shows some activity in sensitizing animals to light.