116 IV. BILE PIGMENTS 



the generic term verdins and its use in the combination mesobihverdin. 

 It suffices to say that this nomenclature has meanwhile been adopted 

 by the Fischer school. 



INIelting point of mesobiliverdin dimethyl ester, prepared from mesobilirubin 

 is 'l\\-^li^2° (SOS), 2^21° (UkSO) and from mesoliemin (f/. Chapter X), 218-219° 

 (/6'<S'/). Siedel (J-VjO) finds a liigher melting point, 2.'}2°. 



Mesobiliverdin dimethyl ester ferrichloride, CiiHviOeN^ • HFeCh, melts at 

 27G° (,SY;.i). 2(;3° {KiSl). 



3.2.3. Other Bilatrienes. Bilatrienes with otlier side chains have not 

 yet been isolated in pure form. Lemberg and Legge (1703) have shown 

 that a bilatriene with oxidized side chains accompanies biliverdin in the 

 reaction mixture obtained by prolonged oxidation of hiliiul)in by hydrogen 

 peroxide. It differs from biliverdin by its somewhat lower light absorption 

 (cmM of hydrochloride 19.0, of biliverdin liydrochloride 28.0) and its higher 

 HCl numl)er. It is not extracted from ether by 2% hydrochloric acid. The 

 existence of this compound has led I'etermann and Cooley {2130) and Malloy 

 and Evelyn (IS-'jJ) to the mistaken belief, based on photocolorimetric data 

 alone, that biliverdin is only a mixture of bilirubin with "a stable blue stage." 



3.3. Reactions and Properties 



Reactions. On treatment with "yellow" nitric acid or with dilute 

 nitrous acid bilatrienes show the later stages of the Gmelin reaction 

 (green-blue-violet-red-yellow). They do not couple with diazotized 

 sulfanilic acid, and occasional statements to the contrary are due to 

 the use of "biliverdin" samples containing bilirubin. Very small 

 amounts of bilatrienes can be found by the following method: to a 

 solution in ammoniacal alcohol some zinc acetate and very small 

 amounts of iodine are added. A blue-green solution with intense 

 red fluorescence and a sharp absorption band in the orange results, 

 due to the formation of the zinc complex salt of a biliviolinoid 

 pigment (c/. Section 5.4.2.). 



The position of this absorption band in the orange part of the 

 spectrum can be used to determine whether the bilatriene contains 

 pro to or meso side chains; in the former case the absorption band is 

 found at about 635 m/Lt, in the latter at about 625 niyu. Bilirubin and 

 mesobilirubin behave similarly (97), but the phenomenon is less 

 striking. 



Absorption curves of biliverdin and of biliverdin hydrochloride are 

 given in Figure 12 and data of the extinction coefficients of biliverdin 

 and mesobiliverdin are given in Table IV.* The maximum of 



* .\11 tlie al).s()r[)ti()ii curves of the "hiliverdiiis" in Heihiieyers hook (121-i) are 

 ohviously tliose of niixtiirt's of liiliverditi witli hiliruliiii (pages 1(51, 1()7) and other 



