METH^MOGOBIN. CYANMETH^EMOGLOBIN. 285 



ammonia. The absorption-spectrum of a watery or acidified solution 

 of methaemoglobin is, according to JADERHOLM and BERTIN-SANS, very 

 similar to that of hsematin in acid solution, but is easily distinguished 

 from the latter since, on the addition of a little alkali and a reducing 

 substance, the former passes over to the spectrum of reduced haemoglobin, 

 while a hsematin solution under the same conditions gives the spectrum 

 of an alkaline h^mochromogen solution (see below). According to 

 ARAKI and DITTRICH, a neutral or faintly acid methaemoglobin solution 

 shows only one characteristic band, a, between C and D, whose middle 

 corresponds to about X = 634. The two bands between D and E are 

 only due to contamination with oxyhaemoglobin (MENZIES, LEWIN, 

 MIETHE and STENGER. According to HASSELBACH'S 1 experience a 

 pure neutral solution of methaemoglobin gives four absorption bands cor- 

 responding to a maxima X = 630, 580, 540 and 500. Methsemoglobin 

 in alkaline solution shows two absorption-bands which are like the 

 two oxyhaemoglobin bands, but they differ from these in that the band 

 is stronger than a. By the side of the band a and united with it by a 

 shadow lies a third fainter band between C and D, near to D. (Spec- 

 trum Plate, 4.) 



The claims as to the action of sodium fluoride upon haemoglobin and methaemo- 

 globin are somewhat contradictory. 2 



Crystallized methaemoglobin may be easily obtained by treating a 

 concentrated solution of oxyhaemoglobin with a sufficient quantity of 

 concentrated potassium-ferricyanide solution to give the mixture a porter- 

 brown color. After cooling to C. add one-fourth vol. cooled alcohol 

 and allow the mixture to stand a few days in the cold. The crystals 

 may be easily purified by recrystallizing from water by the addition 

 of alcohol. According to HASSELBACH this method ordinarily gives 

 impure products while a pure preparation can be obtained by the action 

 of l^ht (see above). 



Cyanmethaemoglobin (cyanhsemoglobin) is, according to HALDANE, identical 

 with photomethaemoglobin (Bocx), which is produced by the influence of sun- 

 light upon a methaemoglobin solution containing potassium ferricyanide. It 

 was first carefully described by R. ROBERT and obtained in a crystalline form 

 by v. ZEYNEK.S It is immediately formed in the cold by the action of a hydro- 

 cyanic-acid solution upon methaemoglobin, but is formed by its action upon oxy- 



1 Jaderholm, Zeitschr. f. Biol. 16; Bertin-Sans, Comp. Rend., 106; Araki, Zeitschr. f. 

 physiol. Chem., 14; Dittrich. Arch. f. exp. Path. u. Pharm., 29; Menzies, Journ. of 

 PhysioL, 17; Lewin and collaborators, footnote 1, page 282; Hasselbach, Bioch. 

 Zeitschr., 19, and Proceedings of the 7th Internat. Congr. of Appl. Chem., London, 

 1909. Important references on methsemoglobin are given by Otto, Pfliiger's Arch., 31. 



2 Piettre and Vila, Compt. Rend., 140; Ville and Derrien, ibid., 140. 



3 Haldane, Journ. of PhysioL, 25; Bock, Skand. Arch. f. Physiol., 6; Robert, 

 Pfliiger's Arch., 82; v. Zeynek, Zeitschr. f. physiol. Chem., 33. See also Leers, 

 Biochem. Zeitschr., 12. 



