INDIVIDUAL BILATRIENES 115 



from ether by 1% hydrochloric acid with blue-green color. Hence 

 some authors stress the green, others the blue, color. 



The AVillstatter method (extraction from ether by hydrochloric 

 acid of graded strength) was first applied in bile pigment chemistry 

 by Lemberg in the investigation of phycobilins {1673) and for the 

 separation of oocyan from protoporphyrin {167 Jf); the method is 

 generally useful for the purification of bile pigments of more strongly 

 basic character. The hydrochloride is only slightly soluble in dilute 

 hydrochloric acid, a property which facilitates purification. It crys- 

 tallizes from concentrated solutions in fine green needles. Biliverdin 

 itself, if sufficiently pure, crystallizes well from methyl alcohol. 



In contradistinction to mesobiliverdin, biliverdin is destroyed by 

 heating with concentrated sulfuric acid. Biliverdin reacts with 

 hydrobromic acid in glacial acetic acid, but the bromoethyl side 

 chains formed are not easily hydrolyzed so that no pure hematobili- 

 verdin results. 



The biliverdin dimethyl ester crystallizes in two forms of different 

 optical properties but with the same melting point and mixed melting 

 point. These forms can be explained by differences in crystal growth 

 (Rawlins, cf. 1680). The melting point of the ester produced from 

 bilirubin is 215-223° C. {1680), of the synthetic ester, 206-209° {863), 

 of the ester from hemin, 208° {1681), and from hemoglobin (by 

 coupled oxidation with ascorbic acid), 216° {1707). 



Biliverdin dimethyl ester f err ichloride, C35Hj806H4' HFeCb, was first 

 described as "green hemin ester" by Warburg and Negelein {2952); 

 its structure was elucidated by Lemberg {1681) {cf. Chapter X). It 

 forms pleochroitic elongated platelets pointed at the ends, and has 

 no definite melting point. Ferric chloride and hydrochloric acid are 

 removed by washing the chloroform solution with water. 



3.2.2. Mesobilatriene, Mesobiliverdin ("Glaucobilin"). This 

 substance C33H38O6N4 was obtained by Fischer and collaborators 

 {803,820) by dehydrogenation of mesobilirubin, and named "glauco- 

 bilin." It can also be obtained by ferric chloride oxidation of meso- 

 bilane and mesobilene-(b) {1680) or by heating mesobilirubin, meso- 

 bilane, and even tetrahydromesobilene in concentrated sulfuric acid. 

 It is very stable and can be heated with sulfuric acid at 100° C. with- 

 out decomposition. In ether solution it is a purer blue than biliverdin. 



Siedel and Fischer {25^5) at first believed that glaucobilin belonged 

 to a class of bile pigments different in structure from biliverdin 

 {cf. 800) and Siedel {2551) objected strongly to the introduction of 



