252 UKOBILIN. 



the chief colouring-substance of normal urine, while present in 

 much larger amounts in the urine of fever. 1 He also obtained it 

 occasionally from bile, the name urobilin thus indicating its double 

 source. In fresh normal urine the amount was frequently ex- 

 tremely small, but was observed to increase on standing exposed 

 to the air (oxygen), a result due to the probable presence in the 

 urine of some chromogen or mother-substance (urobilinogen) 2 of 

 the urobilin. The amount of this pigment in urine is too small 

 to provide adequate material for an elementary analysis, so that it 

 was at first characterised by its solubilities in various fluids, by 

 the strongly-marked fluorescence of certain of these solutions 

 and more particularly by the absorption-spectrum it exhibited. 

 The subsequent preparation of hydrobilirubin from bilirubin, and 

 the establishment of its identity with urobilin (p. 246) provided 

 for the first time a mass of the substance sufficient to admit of 

 analysis, and upon this the formula given above for urobilin is 

 based. It must not however be forgotten that the identity of 

 the two pigments is disputed by several observers, although the 

 balance of belief seems as yet to support it. It will conduce to 

 clearness if we incline for the present to this belief and describe 

 the preparation and properties of urobilin as given by Jaff'^, on 

 the assumption that it is identical with hydrobilirubin, and then 

 subsequently give a short account of the opposing views. 



Preparation from urine. Several methods may be adopted ; of 

 these only the broader facts can here be given, but they suffice 

 to provide solutions which exhibit the characteristic spectra, 

 (i) When urine contained much urobilin Jaffe' precipitated it by 

 the addition of chloride of zinc in presence of an excess of am- 

 monia ; if but little, then by the addition of basic lead acetate. 

 These precipitates were then worked up by processes which do 

 not admit of a suitably brief description. 3 (ii) Precipitate the 

 urine completely by the addition first of normal lead acetate, then 

 of the basic acetate. Wash the precipitates, dry at low tempera- 

 ture, and extract with absolute alcohol (not methylated spirit) 

 acidulated with 1 2 p.c. of sulphuric acid. This extract may 

 be then diluted with water and the pigment extracted by shaking 

 up with chloroform, in which it is readily soluble. 4 (iii) The 

 urine is acidulated with 0*2 p.c. of sulphuric acid and then satu- 

 rated with neutral ammonium sulphate. The precipitate thus 

 obtained is then collected on a filter, washed with an acidulated 

 saturated solution of the ammonium salt, freed by pressure from 

 adhering fluid, and dissolved by gentle warming in absolute alcohol 



1 Centralb. f. d. med. Wiss. 1868, S. 243; 1869, S. 177. Virchow's Arch. Bd. 

 XLVII. (1869), S. 405. 



2 For further references see Xeubauer u. Vogel, Anal. d. Harris. 1890, Sn. 331, 

 336. 



3 For details see Neubauer u. Vogel, he. cit. S. 334. 



4 Mac Munn, Proc. Roy. Soc. pp. 26, 206. Jl. ofPhysiol. Vol. x. (1889), p. 71. 



