40 CHEMICAL PHYSIOLOGY. 



change of the colour to that of purplish or claret until 

 a solution is obtained, which gives the single characteristic 

 absorption band of reduced Hb. This is usually obtained 

 with a solution of Hb of about O2 per cent. 



(b.) Observe the single absorption band less deeply 

 shaded, and with less denned edges between D and E, 

 conveniently designated by the letter 7. It extends be- 

 tween W.L. 595 and 538, and is not quite intermediate 

 between D and E ; is blackest opposite W.L. 550, so that it 

 lies nearer D than E (Gamgee), Both ends of the spectrum 

 are more absorbed than with a solution of oxy-hsemoglobin 

 of the same strength. On further dilution of the solution, 

 the band does not resolve itself into two bands, but simply 

 diminishes in width and intensity. 



3. W.L. of the Spectrum of Carbonic Oxide Haemoglobin. 



(a.) Use a dilute solution of carbonic oxide-haemoglobin 

 of such a strength as to give the two characteristic absorp- 

 tion bands. 



(b.) Observe the two bands, a and /3, like those of Hb-O 2 , 

 but both are very slightly more towards the violet end of the 

 spectrum, a extends from about W.L. 587 to 564, and j8 

 from 547 to 529 (Gamgee). 



(c.) No reduction is obtained by reducing agents. 



4. Preparation of Haematin. 



(a.) Make defibrinated blood into a paste with potassic 

 carbonate. Dry the paste on a water-bath. Place some of 

 the paste in a flask, add 4 volumes of alcohol, and boil on 

 a water-bath. Filter, and an alkaline brown solution of 

 haematin is obtained. Re-extract the residue several times 

 with boiling alcohol, and mix the alcoholic extracts. The 

 solution is dichroic. 



(6.) Acidify the alkaline nitrate of (a.) with dilute sul- 

 phuric acid, filter, and keep the filtrate. Observe the spec- 

 trum of acid-haematin in the filtrate (Fig. 5, 5). 



(c.) Add excess of ammonia to the acid filtrate of (6.), and 

 filter off the precipitate, keep the filtrate, and observe that 



