228 METH^MOGLOBIN. 



let the mixture stand for a short time, and if the band character- 

 istic of methsemoglobin has not made its appearance, add one or 

 two drops more of the solution of the salt and proceed as before. 

 As soon as the bands of oxy-hsemoglobin have markedly disap- 

 peared, acidulate very faintly and examine again. The band 

 which should now be visible as characteristic of methsemoglobin 

 lies in the red part of the spectrum, between C and D, nearer to 

 the former line As already remarked, its position is closely sim- 

 ilar to that of hiematin in acid solution ; but comparison will 

 show that it lies nearer D than does the hsematin band, the 

 centre of the latter being situated at w. L. 640, while that of the 

 former is at w. L. 630 l (See Fig. 37, Nos. 4 and 5). 



In addition to the reagents recommended above, an extensive series 

 of other substances are also found to effect the conversion of oxy- 

 hsemoglobin into methaemoglobin, such as potasssium chlorate, amyl- 

 nitrate, iodine dissolved in potassium iodide, bromine, osmic acid, 

 hydrochinon, pyrocatechin, &c. 2 It may also be obtained as the 

 result of prolonged evacuation with a mercurial pump, of putrefactive 

 changes, or of the action of palladium saturated with hydrogen and 

 immersed in the solution of oxy-hsemoglobin. 3 



The absorption band which has so far been described is the one 

 which is to be regarded as characteristic of methcemoglobin, being 

 accompanied by a very marked absorption of the violet end of the 

 spectrum extending up to the D line. In addition to this band it 

 is stated that, working with a good spectroscope of low dispersive 

 power, three other bands may be additionally seen, 4 two corre- 

 sponding closely with those of oxy-hsemoglobin but not identical, 

 their centres corresponding to w. L. 580 and 539, and the third in 

 the blue at w. L. 500 (?). 5 



In an alkaline solution the position of two of these bands 

 differs slightly from that just given, being stated by Jaderholm 

 to be at w. L. 602 and 578, while the third is unaltered at 

 539. 



In the preparation of large quantities of crystallised oxy- 

 hsemoglobin from pig's blood, it was observed that during the 

 recrystallising essential to its purification a copious crop of 

 reddish-brown crystalline needles was obtained. These were 

 found on examination to be crystals of methsemoglobin. 6 They 



1 This method of localising the bands means that their centres occupy positions 

 in the spectrum where the wave-length of light is respectively 640 and 625 

 millionths of a millimeter. It should always be adopted for all absorption bands, 

 since it is independent of the varying dispersion and arbitrary scales of different 

 spectroscopes. For details see Gamgee, Bhysiol. Chem. Vol. i. p. 94. 



2 For list of substances see Hayem, Compt. Rend. T. en. (1886), p. 698. 



3 Hoppe-Seyler, Zt. f. pjiysiol. Chem. Bd. 11. (1878), S. 149. 



* Jaderholm, Zt. /, Biol. Bd. xx. (1884), S. 419. Also Nord. Med. Arkiv. 

 Abst. in Maly's Jahresb. 1884, S. 113. But see also Araki, Zt. f. physiol. Chem. 

 Bd. xiv. (1890), S. 405. 



5 For figure see Halliburton, Chem. Phi/siol. and Pathol. Fig. 59, Spect. 6, p. 277. 



e Hufner u. Otto, Zt.f.physiol. Chem. Bd. vn. (1883), S. 65. 



