PYRROLE DERIVATIVES. 299 



answered; still there does not seem to be any doubt that there exists 

 an isophonopyrrolcarboxylic acid, which can be obtained from the blood 

 as from the bile pigments. From the mixture of acid cleavage products 

 obtained by the reduction of hsemin with hydriodic acid, and glacial acetic 

 acid PILOTY and DORMANN 1 have obtained as well characterized prod- 

 ucts, phonopyrrolcarboxylic acid and isophonopyrrolcarboxylic acid and 

 also xanthopyrrolcarboxylic acid, CioHisNCb and they consider the 

 existence of this acid as positively proved. The melting-point of the 

 crystalline acid was 108, the picrate 143, and the oxime 208. The 

 corresponding values for isophonopyrrolcarboxylic acid was 122, 146 

 and 210 respectively. An isomeric xanthopyrrolcarboxylic acid, called 

 D-phonopyrrolcarboxylic acid, seems also to occur. 



It is extremely difficult to correlate the somewhat contradictory 

 statements of the various authors in this subject and to draw quite 

 positive conclusions from these statements. It is nevertheless positive 

 that from the hsemopyrrol mixture the three pyrrols, cryptopyrrol, 

 isohaemopyrrol and phyllopyrrol can be obtained and also that there 

 are two hsemopyrrolcarboxylic acids (phonopyrrol- and isophonopyrrol- 

 carboxylic acids), of which one possibly is related to the crypto- 

 pyrrol and the other to the isohaemopyrrol. On account of the uncer- 

 tainty of the experimental foundation it is difficult to enter into a 

 discussion of the variously proposed hypothetical constitutional formulae 

 for the derivatives of the blood pigments. The same is true for the 

 disputed question as to the form of binding of the iron in hsematin and 

 in haemin. It is generally admitted that the iron here is trivalent. The 

 views are different in regard to the valence of the iron in haemoglobin, 

 namely, MANCHOT considers that haemoglobin is a ferric combination 

 while KUSTER 2 on the contrary considers it a ferrous combination. 



Haematoporphyrin gives with hydrochloric acid a compound which 

 crystallizes in long brownish-red needles. If the solution in hydrochloric 

 acid is nearly neutralized with caustic soda and then treated with sodium 

 acetate, the pigment separates out as amorphous, brown flakes not 

 readily soluble in amyl alcohol, ether, or chloroform, but readily soluble 

 in ethyl alcohol, alkalies, and dilute mineral acids. The compound 

 with sodium crystallizes as small tufts of brown crystals and several 

 other salts of haematoporphyrin are known such as the methyl and ethyl 

 esters. The acid alcoholic solutions have a beautiful purple color, 

 which become violet-blue on the addition of large quantities of acid. 

 The alkaline solution has a beautiful red color, especially when too much 

 alkali is not present. 



1 Piloty and Dormann, Ber. d. d. chem. Gesellsch., 46. 



2 Manchot, Zeitschr. f. physiol. Chem., 70; Kiister, ibid., 71. 



