The reduction of methaemoglobin by ascorbic acid.

In idiopathic methaemoglobinaemia, of which we have investigated'some cases, the occurrence of an atypical form of methaemoglobin' abnormally resistant to reduction has been postulated by Lian, Frumusan & Sassier [1939] as an aetiological factor. It thus became of interest to examine the evidence which has been put forward by Vestling [1942] against the unitary view of methaemoglobin. This author found that methaemoglobin made from haemoglobin by the action of nitrite was much less readily reduced by ascorbic acid than methaemoglobin formed by the action of ferricyanide, and suggested that these two spectroscopically similar products [Austin & Drabkin, 1935] differed chemically. The reaction is also of interest because it has been applied clinically by Deeny, Murdock & Rogan [1943] in the treatment of idiopathic methaemoglobinaemia. The experiments reported here indicate that there is no chemical difference between nitriteand ferricyanide-prepared methaemoglobin, so far as reduction by ascorbic acid is concerned, and that the differences observed by Vestling are due to the presence of ferrocyanide.