The combination between methæmoglobin and peroxides : hydrogen peroxide and ethyl hydroperoxide

It was shown by Kobert in 1900 that when hydrogen peroxide is added to a solution of acid methæmoglobin, the solution turns from brown to red and the characteristic absorption spectrum of methæmoglobin is replaced by three diffuse bands at 600-584 mμ, 558-545 mμ, 513-500 mμ. This solution, on standing, and especially on warming, turns brown again and its absorption spectrum rapidly reverts to that of the ordinary acid methæmoglobin. Kobert concluded that the red solution thus obtained is a loose combination between methæmoglobin and H2O2 which he called “Wasserstoffsuperoxydmethemoglobin.” Kobert’s observation was confirmed only in 1924 by Haurowitz, who noticed that acid methæmoglobin on addition of H2O2 changes its colour and its absorption spectrum. He did not, however, ascribe this change to the formation of H2O2- methæmoglobin but to the transforma­tion of acid methæmoglobin into aikaline methæmoglobin (p. 25). In a later paper in 1931 Haurowitz repeated his observations, using this time a recrystallized preparation of methæmoglobin, and found that : “the two banded absorption spectrum of this solution remained un­changed on the addition of potassium ferricyanide or of sodium cyanide ; also a great excess of Na2S2O4 did not bring about the appearance of the absorption bands of hæmoglobin, while methæmoglobin and its deriva­tives when treated in this way are easily transformed into hæmoglobin. The spectroscopic appearance of the preparation resembles also that of NO-hæmoglobin.” According to this statement the methæmoglobin treated with H2O2 does not seem to form a H2O2-methæmoglobin as was postulated by Kobert.