On the combinations of methæmoglobin with H 2S

Seventy years ago Hoppe-Seyler (1863) found that if a current of H2S is passed through a solution of oxyhæmoglobin a distinct adsorption band appears in the red end of the spectrum and the compound turns gradually green. He found further that this change takes place only when H2S acts in presence of oxygen, and the compound thus obtained he described as sulpho-methæmo-globin. Similar results have been obtained by several other workers and especially by Lewisson (1866) and by Araki (1890) who have shown, rnoreover, the co-existence of the absorption hands of sulpho-hæmoglobin with those of oxy- or reduced hæmoglobin. Harnack (1899), to whom we owe a careful revision of the whole literature of the subject, repeated these observations but claimed to obtain the appearance of the absorption hand in the red end of the spectrum by passing H2S through a solution of reduced hæmoglobin kept under a layer of paraffin, believing the reduced hæmoglobin to be thus sufficiently protected from oxygen. He concluded that "sulpho-hæmoglobin" can be obtained in complete absence of oxygen, although he agrees with Hoppe-Seyler that only in the presence of oxygen is hæmoglobin transformed by H2S into the green compound. More recently Haurowitz (1926) described as “sulpho-hæmoglobin” a green compound which he has obtained from hæmoglobin by passing through it at frequent intervals during a whole week currents of H2S and of oxygen. He described also methods of obtaining the crystals of this compound, showing the absorption band at 618 mμ. Treated with alkali and Na2S2O4 this compound gave an ordinary proto-hæmochromogen. The porphyrin obtained from this compound did not differ from protoporxhyrin in its solubilities and absorption spectrum. These facts indicated that prolonged treatment with H2S and O2 does not affect the prosthetic portion of the hæmoglobin molecule. The analysis of crystals gave 16 atoms of sulphur per each atom of iron, a result which seems to indicate that most, if not all, of the sulphur found was adsorbed to the crystals.