HAEMOCHROMOGEN. 255 



to the relations of haemochromogen to haemoglobin, and the part which 

 it plays in relation to the optical properties of, and the chemical affinities 

 for gases manifested by, the complex molecule of haemoglobin. 



Methods of preparing solutions containing hcemochromogen by the direct 

 decomposition of hcemoglobin. Without referring to a more complicated 

 and in some respects more satisfactory method of decomposing haemo- 

 globin in the absence of oxygen, 1 the following very simple method, 

 which, like the first, we owe to Hoppe-Seyler, 2 will be described. 



A solution of oxyhaemoglobin is placed in a glass tube, and then a 

 smaller glass tube containing a solution of sodium or potassium hydrate, 

 or, if desired, of tartaric or phosphoric acid, is introduced into the larger 

 tube, the open end of which is then drawn out and sealed in the blow- 

 pipe name. The apparatus thus prepared is then subjected to gentle 

 heat, taking care not to incline the tubes so as to cause their contents 

 to mix. 



The oxyhaemoglobin contained in the larger, outer tube first becomes 

 reduced, and thereafter the oxygen contained in the air of the tube is 

 absorbed by the haemoglobin. When many days have elapsed, and the 

 whole of the haemoglobin is again reduced, the tubes are inverted and 

 their contents mixed, when the formation of haemochromogen may be 

 followed by the changes in colour and in the spectrum, which the 

 colouring matter undergoes. 



Physical and chemical properties. When acted upon by dilute solu- 

 tions of the caustic alkalies, haemochromogen gives rise to a beautiful 

 cherry-red solution, which, when sufficiently diluted, exhibits two 

 absorption-bands apparently identical with those of Stokes' reduced 

 haematin, which have already been referred to. 



The visible spectrum of solutions of haemochromogen in alkaline 

 solutions is distinguished from all others by the extraordinary intensity 

 and sharpness of the absorption-band nearest to D. The second ab- 

 sorption-band, which is very much less intense, has less sharply-defined 

 borders. The solution, even when concentrated, absorbs very little of 

 the red. 



The following are measurements of the position of the absorption- 

 bands in the visible spectrum by Hoppe-Seyler and myself : 



Gamgee's measurements 3 (1878) X 567-547 A 532-518 



Hoppe-Seyler's 4 (1889) X 565-547 X 527-514 



My study of the photographic spectrum of haemochromogen has led 

 to the following results : 5 Solutions, even of very great dilution, exhibit 

 an absorption-band between h and g. This band has the same position 

 as the band of CO-haemoglobin, but is much more intense. With one 

 part of haemochromogen in 25,000 parts of water, a stratum 10 mm. thick 

 being examined, an intense absorption-band occupies the region between 

 X410'0 and X430'0. From the examination of solutions of various strengths 

 it results that the mean ray absorbed corresponds to about A 420 '0. 



By heating to 110 C. a solution of haemochromogen mixed with 

 a sufficiently concentrated solution of sodium hydrate, haemochromogen 



1 Hoppe-Seyler, Med.-chem. Untersuch., Berlin, S. 540 and 541 ; and Gamgee's 

 "Physiological Chemistry," vol. i. pp. 118 and 119. 



2 "Physiol. Chem.," 1878, S. 390. 



3 "Physiological Chemistry," 1880, vol. i. p. 111. 



* Ztsctir.f. pliysiol. Chem., Strassburg, 1889, Bd. xiii. S. 496. 

 5 Gamgee, Proc, Roy. Soc. London, 1896, vol. lix. p. 276. 



