254 H.-EMOGLOBIN. 
The compounds of hsematin with acids, e.g. haeniatin-hydrochloride, 
present, even in solutions of great dilution (1 : 25,000-1 : 50,000), an 
intense absorption - band, which encroaches more and more on the 
ultra-violet, as the strength of the solution increases. In a solution con- 
taining one part of crystallised hamiatin hydrochloride in 20,000 parts 
of glacial acetic acid, the band extends between h and M, the most 
intense absorption between h and L. The less refrangible border of this 
band is sharply defined, whilst the more refrangible border is less 
definite. As the solution is diluted the band becomes narrower, 
through less and less of the ultra-violet 1 >eing absorbed. In highly dilute 
solutions the band which is still intense absorbs both H and K. 1 
The acid compounds of htematin exbibit, therefore, an absorption- 
band, which is exactly on the boundary of the ultra-violet proper, and 
which extends further and further into the ultra-violet as the con- 
centration of the solution increases. 
G HK L M NO 
Fig. 37. — The photographic spectrum of hserain. 
HiEMOCHROMOGEN (SYN. " KEDUCED ILeMATIN "). 
It lias already been explained that Hoppe-Seyler employed the 
name haemochroinogen to denote the very remarkable body which he 
was the first to study with care, and which results from the decomposi- 
tion of reduced haemoglobin, in the absence of all oxygen, by acids, and 
especially by alkalies, and of winch the solutions present absorption- 
bands in the visible spectrum, which are identical with those of the 
reduced heematin of Stokes. 
The latter name had been applied by Stokes to the chemical 
substance assumed to be the cause of the characteristic absorption- 
spectra which are exhibited by solutions of the blood-colouring matter, 
and likewise by impure solutions of heeniatin when subjected to the 
action of reducing agents. It now remains to describe the methods of 
preparing solutions of haemochroniogen, the body itself and its properties 
(so far as these are known to us), its combinations, and especially to 
refer to the views which Hoppe-Seyler advanced and held, in reference 
1 Gamgee, Proc. Roy. Soc. London, 1896, vol. lix. p. 276. 
