DECOMPOSITION OF H/EMOGLOBIN. 33 



gramme Hb unites with 1*33-1 '35 c.c.m. of each of the gases at 

 and 1 metre pressure (Preyer, L. Hermann). 



(5.) Cyanogen, CNH (Hoppe-Seyler), and acetylene, C 2 H 2 (Bistrow and 

 Liebreich), form easily decomposable compounds with Hb. The former occurs in 

 poisoning with hydrocyanic acid, and has a spectrum identical with that of 2 Hb, 

 and, like 2 Hb, it is reduced by special agents. [The existence of these com- 

 pounds is, however, highly doubtful (Gamgee).] 



(6.) If C0 2 be passed through a solution of qxyhsemoglobin for a con- 

 siderable time, reduced Hb is first formed; but if the process be 

 prolonged the" Hb is decomposed, a precipitate of globulin is thrown 

 down, and an absorption-band, similar to that obtained when Hb is 

 decomposed with acids, is observed (see p. 33). 



18. Decomposition of Haemoglobin. 



In solution and in the dry state Hb gradually becomes decomposed, whereby 

 the iron-containing pigment hsematin, along with certain bye-products, formic, 

 lactic, and butyric acids are formed. 



Haemoglobin, however, may be decomposed at once into (1) a body 

 containing iron hcematin, and (2) a colourless proteid closely related to 

 globulin; by (a.) the addition of all acids, even by C0 2 in the presence 

 of plenty of water ; (b.) strong alkalies ; (c.) all reagents which coagulate 

 albumin, and by heat at 70-80C. ; (d.) by ozone. 



(A.) HSEMATIN (Cgg, H 70 , Ng, Fe 2 , 10 ) forms about 4 per cent, of haemo- 

 globin (dog). It is insoluble in water, alcohol, and ether; soluble in 

 dilute alkalies and acids, and in acidulated ether and alcohol. 



When Hb containing is decomposed, hsematin is formed at once ; while Hb 

 free from on being decomposed forms first a purplish-red body, ILEMOCHROMOGEN 

 (C 34 , H 36 , N 4 , Fe 5 ), which contains less 0, and is a precursor of haematin. In 

 the presence of O it becomes oxidised, and passes into hsematin. In solution it 

 gives the spectrum shown in Fig. 11, 7 (Hoppe-Seyler). Dilute acids in an 

 alkaline solution deprive hsemochromogen of its iron, and H^MATO-PORPHYRJN, a 

 substance which remains stable in contact with ah", is produced. It may also be 

 produced from haematin by the action of acids, so that hsematin is an oxidation 

 stage of hsemochromogen. 



(a) Hcematin in acid solution. Lecanu extracted it from dry blood-corpuscles 

 by using alcohol containing sulphuric and tartaric acids. If acetic acid be added 

 to a solution of Hb, a mahogany-brown fluid is obtained, containing hcematin in acid 

 solution, which gives a spectrum with fovr absorption-bands in the yellow and 

 green (Fig. 11, 5). 



(/3) If this solution be treated with excess of ammonia, hcBmaiin in alkaline solu- 

 tion is formed, which gives one absorption-band on the boundary line between red 

 and yellow (Fig. 11, 6). 



(y) Reducing agents cause this band to disappear, and produce in the yellow 

 two broad bands, which are due to the presence of " reduced hcematin " (Fi?. 

 11, 7). 



(5) When haemoglobin is extravasated into the subcutaneous tissue, it becomes 

 so altered that ultimately hydrated oxide of iron appears in its place. 



3 



