254 UROBILIN. 



description 1 , (ii) Precipitate the urine completely by the addition 

 first of normal lead acetate, then of the basic acetate. Wash the 

 precipitates, dry at low temperature, 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 ex- 

 tracted by shaking up with chloroform, in which it is readily soluble 2 , 

 (iii) The urine is acidulated with 0-2 p.c. of sulphuric acid and then 

 saturated 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 

 to which if necessary a few drops of ammonia have been added 3 , 

 (iv) Frequently from normal urine, the more readily if that be highly 

 coloured, a solution of urobilih may be obtained by simple agitation 

 with chloroform, or by gently shaking it up with half its volume 

 of pure ether free from all traces of alcohol. The ether is then 

 removed by a separating funnel, evaporated at ordinary temperatures 

 and the residue dissolved in a small quantity of absolute alcohol 4 . 



If the alcoholic or chloroformic solutions above described are 

 evaporated to dryness at a low temperature, the urobilin remains as 

 a yellowish-brown amorphous pigment, which is practically insoluble 

 in water except in presence of small amounts of neutral salts, very 

 slightly soluble in either ether or benzol, readily soluble in alcohol and 

 in chloroform. The neutral alcoholic solutions if dilute are. yellow 

 with a rosy tint, and if strong show a green fluorescence. The acid 

 solutions are reddish-yellow, or if dilute bright rose-coloured and do 

 not fluoresce. Alkaline (alcoholic) solutions are yellow or yellowish- 

 green according to the concentration and usually show a marked 

 fluorescence, which is much increased on the addition of a solution 

 of zinc chloride, appearing now rose-coloured by transmitted light and 

 brilliant green by reflected. 



Spectra of urobilin. Neutral or alkaline alcoholic solutions show 

 one absorption band between b and F. In alkaline solution the band 

 is frequently very faint, but is more strongly marked after the addition 

 of zinc chloride, so much so that it can often only be distinctly seen 

 after the addition of this salt. In acid solutions a similar band is 

 seen, situated however in this case slightly more towards the violet 

 end of the spectrum. 



1 For details see Neubauer u. Vogel, loc. cit. S. 334. 



MacMunn, -Proc. Roy. Soc. pp. 26, 206. Jl of Physiol. Vol. x. (1889), p. 71. 

 Mehu, Journ. d. pharm. et de chim. T. xxvm. (1878), p. 159. This method is 

 good, as avoiding to a considerable extent any alteration of the pigments by the 

 process employed. 



4 E. Salkowski, Zt. f. physiol. Chem. Bd. iv. (1880), S. 134. 



