THE INDIVIDUAL GROUPS OF PROTEINS 485 



Acid H(SDiatoporphyrin. 



(a) A few drops of blood are mixed with 5 c.c. of concentrated 

 sulphuric acid. A purple solution is obtained, which, when examined 

 with the spectroscope, will show two well-marked absorption bands. 

 One of the absorption bands lies in the orange between C and D ; 

 the other, which is broader and darker, lies in the yellow-green be- 

 tween D and E. The solution may be diluted with glacial acetic 

 acid, if necessary. 



(b) Blood which has stood for 2-3 days in the cold, i.e. has be- 

 come reduced by standing, is treated with one-third of its volume of 

 concentrated hydrochloric acid and filtered. The mass of haematopor- 

 phyrin and precipitated proteins is extracted with alcohol ; the alcoholic 

 filtrate shows the spectrum of acid haematoporphyrin (Laidlaw). 



Alkaline Hamatoporphyrin. 



(a) The sulphuric acid solution of haematoporphyrin is poured into 

 excess of distilled water. The solution is cooled and neutralised with 

 caustic soda. A pigmented precipitate containing most of the haema- 

 toporphyrin separates out. Sodium acetate makes the precipita- 

 tion more complete. The precipitate is filtered off and dissolved in 

 dilute caustic soda. The solution of alkaline haematoporphyrin so ob- 

 tained shows, when examined with the spectroscope, four absorption 

 bands, a narrow one in the red, a broader and darker one in the green, 

 a third in the green extending to the violet side of E and a fourth at 

 the junction of the blue and green. 



(b) On rendering the hydrochloric acid solution just alkaline with 

 ammonia, the spectrum of alkaline haematoporphyrin may be observed. 

 It is, however, best seen if the alcoholic solution be evaporated to dryness 

 on the water-bath and the pigment dissolved in dilute ammonia. 



