496 CHEMISTRY OF THE PROTEIDS CHAP. 



mineral acids are allowed to act for a limited time on haemoglobin there 

 is formed acid-haemoglobin, according to Harnack (see, however, below). 

 Stokes and Hoppe-Seyler, 1 Preyer 2 and Strassburg, 3 have considered 

 Harnack's acid-haemoglobin 4 to be methaemoglobin, and have supposed 

 dilute acids to act in the same way as do potassium ferricyanide, 

 amylnitrite, etc. 



Acid-haemoglobin, according to Harnack, is brown, like methaemo- 

 globin, and resembles the latter also greatly in its absorption-spectrum, 

 but the band in the red lies more towards the red end, namely, on 

 either side of the C-line, while the methaemoglobin band only reaches 

 up to C ; the band of acid-haematin, which also lies in the red, is still 

 more to the red than is the acid-haemoglobin band. Strassburg has 

 pointed out that the oxygen capacity of haemoglobin is inversely 

 proportional to the amount of acid which is added to the haemoglobin; 

 the greater the amount of acid, the less oxygen is taken up, and Ham 

 and Balean, 5 who have made a very careful study of the effect pro- 

 duced on haemoglobin by the addition of different strengths of acid, 

 as already stated on p. 474, have observed that a strength of acid 

 can be found which only displaces the carbon-dioxide, leaving oxy- 

 haemoglobin in solution. If, however, the acid is increased in strength, 

 a small quantity of oxygen is liberated, and on spectroscopic examina- 

 tion there is seen a faint band in the red, placed between the position 

 of the methaemoglobin and acid-haematin bands, but more nearly 

 approaching that of acid-haematin ; there are also present the bands 

 of oxyhaemoglobin. If now ammonium sulphide be added, the 

 band in the red disappears and those of oxyhaemoglobin give place 

 to the broad band of reduced haemoglobin, and at the moment of 

 adding the acid, the dark band of haemochromogen (i.e. reduced 

 haematin) appears along with the broader band of reduced haemoglobin, 

 but the haemochromogen band rapidly fades, leaving only the bands 

 of reduced haemoglobin. Ham and Balean believe this to 'be con- 

 clusive proof that on the addition of weak acids to oxyhaemoglobin 

 there results a mixture of oxyhaemoglobin and acid-haematin, while it" 

 sufficient acid be added to replace one-half of the replaceable oxygen, 

 only one strong band, characteristic of acid-haematin, is found. 



The author is therefore inclined to regard Harnack's acid-haemo- 

 globin as simply a mixture of oxyhaemoglobin and acid-haematin. - 



1 F. Hoppe-Seyler, Virchmo's Arch. 29. 233 (1864) ; Zentralbl. f. d. mediz. 

 Wissensch. 1865, p. 65. 



2 W. Preyer, Pfiugers Arch. f. d. ges. Physiol. 1. 395 (1868) ; and in Blutkris- 

 talle, Jena, 1871. 3 G. Strassburg, Pfliiger's Arch. f. d. ges. Phys. 4. 454 (1871). 



4 E. Harnack, Zeitschr. f. physiol. Ohem. 26. 558 (1899). 



5 C. E. Hani and H. Balean, Journ. of Physiol. 32. 312 (1905). 



