H^MATOPORPHYRIN. 259 



(Hoppe-Seyler) ; (2) by the action of acetic acid saturated with HBr, 

 aided by heat (Nencki and Sieber). 



Hsemochromogen is, in the absence of oxygen, converted even by the 

 weakest acids into hajmatoporphyrin, the iron being found in the 

 solution as the ferrous salt of the acid employed. Although occurring 

 more slowly, the decomposition of CO-haemochroinogen by acids also 

 yields htematoporphyrin. 



According to Hoppe-Seyler, the composition of hsematoporphyrin is 

 represented by the formula C 34 H 3 , J N 4 ( .. 



According to Nencki and Sieber, who have made the most complete 

 investigation of this body, it has the composition C 16 H 18 N 2 3 , and they 

 explain its origin from hsematin by the following equation, in which 

 they adopt their own as distinguished from Hoppe-Seyler 's formula for 

 hsematin 



C 32 H 30 N 4 Fe0 3 +3H 2 = 2(C 16 H 18 N 2 8 +Fe) 



(htematin) 



According to Nencki and Sieber, hsematoporphyrin is isomeric with 

 bilirubin. 



G h HKLM NO 



FIG. 39. The photographic spectrum of hsematoporphyrin. 



Physical and chemical properties. Hsematoporphyrin forms beauti- 

 ful crystalline compounds with Na and with HCL 



It is insoluble in pure distilled water, slightly soluble in dilute acids, 

 more soluble in strong acids, and readily soluble in alkaline solutions, 

 weak and strong. It is also readily soluble in acid and alkaline alcohol. 



Solutions of hsematoporphyrin in acidulated alcohol have a beautiful 

 purple colour, and assume a bluish violet tint when the solution is made 

 very strongly acid. Alkaline solutions are of a fine red, but in the 

 presence of a great excess of alkali exhibit a violet tint. Solutions of 

 haematoporphyrin, even if extraordinarily dilute, exhibit a magnificent 

 red fluorescence, which strangely enough is not referred to in text-books, 

 though it seems to me to be their most remarkable characteristic. 



An alcoholic solution of haematoporphyrin, acidulated with hydro- 



