142 



IV. BILE PIGMENTS 



estimations of urobilinogen and stercobilinogen were based on the 

 data obtained with mesobilane, while the chromogen predominant 

 in urine and feces is tetrahydromesobilane. 



Tetrahydromesobilene-{b) (neutral) has a melting point of 236° C. 

 (822). The monohydrochloride was purified by Watson and, later, 

 both Heilmeyer {1218) and Watson {297If) found a dihydrochloride. 

 The latter, however, easily loses one molecule of hydrochloric acid on 

 drying at 65° C. (2981). Crystallized from acetone both melt at 

 146-149° C, from chloroform at 125-128° C. With ferric chloride 

 stable ferrichlorides of stercobilin (m.p. 187-190° C.) and its dimethyl 

 ester (m.p. 160-162° C.) are formed (2981). The optical rotation of 

 a solution of the hydrochloride in chloroform is very strong, [ajs^s" = 

 - 3500° (822,823). 



According to Heilmeyer and Beickert {1215) the hydrochloride is oxidized 

 by hydrogen peroxide or by chloric acid to a red compound, rubrobilin. 

 Its absorption band in acid solution lies at 520 m/x. 



TABLE X 



Absorption Spectra of Tetrahydromesobilene-(b) and Its Compounds 



" Position measured by Pruckner and Stern spectrophotometrically, by Lemberg with 

 the Hartridge Reversion Spectroscope. Lemberg and co-workers {1713) found the 

 b.infl position 490. G m^i in the visual spectrophotometer, 487.0 m/u in the ultraviolet 

 spectrophotometer. 



''Not clearly distinguishable from zinc mesobilene-(b) band. 



